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                           Biogas Systems in India
                            by Robert Jon Lichtman
                       Illustrations by William Gensel
                      1600 Wilson Boulevard, Suite 500
                        Arlington, Virginia 22209 USA
                  Tel:   703/276-1800 * Fax:   703/243-1865
                             in cooperation with
                   The Committee on Science and Technology
                      for Developing Countries (COSTED)
                      Central Leather Research Institute
                         Adyar, Madras 600 026 India
                     This publication is one of a series
                  issued by VITA to document the activities
                  of its worldwide Renewable Energy Program.
                             ISBN 0-86619-167-4
           Composed and produced in Arlington, Virginia, by VITA, Inc.
                [C] 1983, Volunteers in Technical Assistance, Inc.
                                Table of Contents
Abbreviations and Terminology
I.     Rural Energy Consumption and Biogas Potential
II.    An Overview of Biogas Systems
III.   Digester Designs
IV.    System Operation
V.     Gas Distribution and Use
VI.    Economic Analysis of a Village System
VII.   Village Utilization
VIII. Conclusions and Recommendations
An important common theme underlies much of the current literature
on the application of technology within both developed and
developing nations.  Any technology has a complex series of
impacts on the environment in which that technology operates.
The concern over a technology's "appropriateness" is based on
the need to determine clearly who will be affected by use of
the technology and in what ways.
Behind the concept of "appropriate technology" is the belief
that the complex interactions between a technology and its
environment should be made "visible."  Only then can a technology
be evaluated properly.  By describing explicitly the impact
of a technology, the selection criteria for the technology also
become explicit.  If we choose a technology that pollutes a
river, but which also provides permanent jobs for 10,000 workers,
we presumably either value employment benefits over
environmental costs or else were ignorant of the pollution
effects at the time we made the decision.
The choice of a technology is "appropriate" or "inappropriate"
only in the context of the demands we place upon it.  The subtle
trade-offs between these often conflicting demands are at the
real core of any debate over the choice of a technology.  Appropriate
technology is less a problem of hardware than of appropriate
data collection, decision-making, financing, installation,
and use--with all the problems of sorting out competing
demands and value judgements in each of these tasks.
This study is an assessment of the "appropriateness" of biogas
technology in meeting some of the needs of India's rural population.
Such an assessment is quite complicated, despite claims
that a biogas system is a simple village-level technology.
While there is evidence that biogas systems have great promise,
they are subject to certain constraints.  It is impossible to
describe here all the factors that one might study to assess
any technology.  I only hope that the approach used in this
study will help others.
One difficulty in studying biogas technology is the fragmented
and often anecdotal nature of the research and development
work.   In order to provide this snapshot of the state-of-the-art
in India, I have had to enlist the aid of a bewildering number
of government officials, industrialists, university researchers,
missionaries, social workers, journalists, voluntary
groups, farmers, merchants, and villagers.  While I will
never be able to express fully my gratitude to the hundreds of
people who have helped me piece this puzzle together, I am
particularly indebted to the following:
    Dr. A.K.N. Reddy, and the ASTRA team, Indian Institute of
    Science, Bangalore; K.K. Singh, PRAD, State Planning
    Institute, Lucknow; Dr. Ram Baux Singh, Etawah; T.R.
    Satishchandran, Energy Adviser, Planning Commission,
    Government of India; Dr. S. Shivakumar, Madras Institute
    of Development Studies; Dr. C.R. Muthukrishnan, IIT,
    Madras; John Finlay and David Fulford of Development and
    Consulting Services, Butwal Technical Institute, Butwal,
    Nepal; D. Kumar and M. Sathianathan, Center for Science
    for Villages, Wardha; Dr. C.V. Seshadri and Rathindranath
    Roy, Murugappa Chettiar Research Centre, Madras; C.R. Das,
    Coordinator, Tata Energy Research Institute, Bombay; and
    the staff at the Central Leather Research Institute,
    Madras, all of whom were extremely helpful, generous, and
    patient with a stranger in a strange land.
I am extremely grateful to Dr. S. Radhakrishnan, Scientific
Secretary of the Committee on Science and Technology in Developing
Countries (COSTED), Indian Institute of Technology,
Madras, for his constant trust and financial support throughout
the course of my research.  John Westley and the staff of the
U.S. Agency for International Development (USAID), New Delhi
Mission, provided both editing and typing assistance, as well
as a research grant (USAID/India Purchase Order IN-P-O-67).  The
staff of Volunteers in Technical Assistance (VITA) spent many
long hours editing the final manuscript and bringing it out in
its present form.  Of course, the views expressed in this study
are my own, and do not represent the official position of VITA,
USAID, the U.S. Government, or any other body.
Finally, I am deeply indebted to Dr. Y. Nayudamma, Distinguished
Scientist, Central Leather Research Institute, Madras.
without his guidance, friendship, and unyielding support, none
of this would have been possible.  All of these individuals have
immeasurably deepened my understanding of biogas technology, as
well as of India itself.  Any errors or omissions contained in
this study are due to my own failure to utilize their considerable
                                           Robert Jon Lichtman
                                           December 1982
Abbreviations and Terminology
BHP        = brake horsepower
crore      = 10,000,000 rupees
hr         = hour
kcal       = kilocalorie (1,000 calories)
kwh        = kilowatt-hour
lakh       = 100,000 rupees
[m.sup.3] = cubic meter
MT         = million tonnes
MTCR       = million tonnes of coal replacement
Rs         = Indian rupee(s)
tonne      = metric ton (1,000 kg)
Rs 1.00    =  US$0.125 at the time of this study
The term "biogas" system is somewhat of a misnomer.   Though
biogas systems are often viewed as an energy supply technology,
the Chinese regard their systems primarily as a means to provide
fertilizer and the sanitary disposal of organic residues.
Gas is considered a useful by-product.(1)  In India, interest in
biogas is due to its potential as a fuel substitute for firewood,
dung, kerosene, agricultural residues, diesel, petroleum,
and electricity, depending on the particular task to be performed
and on local supply and price constraints.  Thus, biogas
systems provide three primary products:  energy, fertilizer, and
waste treatment.  For the sake of convenience, the term "biogas
system" in this study will refer to the technology of digesting
organic wastes anaerobically to produce an excellent fertilizer
and a combustible gas, and to dispose of agricultural residues,
aquatic weeds, animal and human excrement, and other organic
While use of biogas systems is not restricted to rural areas,
the difficulties of retrofitting such systems in urban areas,
supplying a balanced charge of biomass, generating adequate
pipeline pressure, and minimizing capital costs all suggest
that biogas systems will be more easily adapted, in the short
term, to rural areas.  This study therefore is focused on rural
utilization of biogas systems.(2)
                 I.   Rural Energy Consumption
                      and Biogas Potential
Biogas has great potential for supplying energy for cooking,
lighting, and small-scale industry in rural India.  This section
will show through a series of calculations that biogas theoretically
can play a significant, if not major, role in meeting
many of these needs, as well as in supplying fertilizer and
helping to solve other development problems.  Readers not
interested in these calculations should skip to Section II on
Page 11; the important point is that biogas holds considerable
promise and deserves further study.
To assess properly the potential of biogas systems for meeting
a variety of rural needs, one would have to know the total
amount of organic material (biomass) available annually; that
is, material for which there are no other more productive uses.
Biomass that could be employed as feed material would have to
be studied carefully with respect to the annual output of each
material, the average biogas yield per unit of material, collection
and transportation costs, and the availability of the
material over time.
Unfortunately such data do not exist in India with any degree
of reliability.  No accurate data exist on the annual supply of
water hyacinth, congress grass, banana stems, and other biomass
that can serve as a feed material to a biogas system.
Since many agricultural residues are used as fodder, knowledge
of the net availability of these residues is important to avoid
conflicting demands on their use.  Statistics on the amount of
residue per crop, though available, tell nothing of the end use
of the residue.  Revelle cites aggregate figures of 34-39 MT of
crop residues consumed annually as fuel.(3)
Even annual dung output is a matter of some controversy.  Desai
estimates that out of the 114-124 MT (dry weight) of dung produced
annually, about 36 MT dry weight are burned as fuel.(4) The
Working Group on Energy Policy calculates that 73 MT of dung
are used as fuel,(5) without specifying if this is a dry weight
figure (dry weight = approximately 1/5 of wet weight).  Revelle
uses a World Bank estimate of 68 MT burned as fuel (out of a
total of 120-310 MT) and suggests that 83 percent of this, 56
MT (dry weight), is consumed in rural areas.(6)
The Indian Ministry of Agriculture offers data on livestock
Population and dung voided per animal per annum as shown in
Table I-1.  Again, there is uncertainty about the percentage of
dung produced in rural areas.  To be conservative, we will
assume that there are roughly 237.5 million cattle, buffalo,
and young stock (from Table I-1), and that their collectible
daily yield from night droppings (when cattle are tied up near
a dwelling) is approximately 8.0 kg per head.(7)  Using Revelle's
estimate of rurally produced dung at 83 percent of the total,
annual rural dung production would be over 575.6 MT wet weight,
or 115.1 MT dry weight.
Various estimates shed little light on the percentage of dung
collected, or on factors affecting dung output, such as cattle
species, body weight, diet, etc.  Data will also vary regionally
and seasonally.  If we assume that there is a 20 percent weight
loss during collection of the 115.1 MT dry weight of rural dung
(calculated above), then the net available dung is 92.1 MT.  To
this can be added 34 MT dry weight of crop residues that are
burned annually.  This gives a total of about 126 MT (dry) of
biomass that is available for biogas systems.  Assuming an
average gas yield of 0.2 [m.sup.3]/kg (dry) for the biomass(8) and a
calorific value of 4,700 kcal/[m.sup.3] for biogas(9), the available
biomass would yield roughly 25 billion [m.sup.3] for biogas.  This is
     Table I-1   Potential Annual Availability of Dung (1972)(10)
                   Number of        Daily         Output/hd.    Total
                   Animals          Output/       (millions     (millions
Livestock           (Millions)       Head (kg)    of tonnes)    of tonnes)
Cattle                131.4             10           3.65         479.6
(3 + years old)
Buffalo                37.8             10           3.65         138.0
(3 + years old)
Young stock           68.3              3.3          1.20          82.0
Sheep and goats      108.4              1.1           .4           43.4
                                               TOTAL            743.0
Total = 743 MT (wet weight)
Total minus 20 percent collection loss  =   594.4 MT (wet weight)
                                        =   118.9 MT (dry weight)
equivalent to 118 trillion kcal.  This estimate probably is low,
because it does not include numerous weeds and aquatic biomass
that might be used as a feedstock for biogas plants, but which
currently have no alternative uses.
Assuming biogas burners have a thermal efficiency of 60 percent,
the potential net energy for cooking from biogas is
roughly 71 trillion kcal per annum.  Approximately 975 trillion
kcal are currently consumed during the burning of dung, firewood,
charcoal, and crop residues for domestic use (cooking,
water heating, etc.).(11)  Of that figure, 87 percent is used in
cooking.(12)   Therefore, approximately 848 trillion kcal per annum
is consumed in cooking in rural India.  This figure, when combined
with a 10 percent average thermal efficiency of
"chulahs"(13) (mud/clay stoves) and the vast number of open
cooking fires, gives a net energy consumption of approximately
85 trillion kcal per annum for cooking.  We will assume that
rural cooking needs consume about 85 percent of this figure, so
that the annual net energy consumption for rural areas is 72.3
trillion kcal.  Thus, biogas can essentially provide the net
usable energy currently consumed in cooking from all noncommercial
fuel sources in rural India.
The amount of total solids in biogas slurry prepared from 126
billion kg (dry weight) of organic matter, the minimum amount
annually available for fuel and fertilizer (from our previous
calculations), is roughly 630 billion kg (wet weight), assuming
for simplification that both plant wastes and dung contain 20
percent solids.
Given current practices, this biomass would be mixed with water
at a 1:1 ratio if it was to be fed into a biogas system.   The
total influent would weigh 1.2 trillion kg.  Twenty percent of
this would be lost during microbial digestion.  Of the remainder,
the percentage of total solids per kg of weight of slurry
would be about 6.4 percent.  The digested biomass thus would
contain 61 MT of solids.
Table I-2 shows the relative fertilizer content of biogas
slurry and farmyard manure.(14)  Based on this table, 61 MT of the
total solids in biogas slurry would yield approximately 1.037
MT of nitrogen (N), .976 MT of phosphorus pentoxide ([P.sub.2][O.sub.5]), and
.610 MT of potassium monoxide ([K.sub.2.O]) per annum.
Without a more detailed picture of the current end uses of
organic residues, it is difficult to assess accurately the
potential impact of a large-scale biogas program on overall
fertilizer supply.  Importation of chemical fertilizer is a
function of the gap between demand and domestic production.
Domestic production is comprised of indigenous production of
chemical fertilizers and the use of organic residues and wastes
that are composted as farmyard manure.  Any net increase in the
                          Table I-2
Average Fertilizer Value of Biogas Slurry and Farmyard Manure
                    (Percentage of dry weight)
Substance                       N       [P.sub.2][.O.sub.5]        [K.sub.2.O]       Total
Biogas slurry                 1.7       1.6        1.0       4.25
Farmyard manure + compost     1.0       0.6        1.2       2.8
amount of fertilizer derived from organic residues can be used
to offset imports, assuming of course that domestic production
of chemical fertilizers remains constant.  The net increase in
available fertilizer attributable to biogas slurry is derived
from the following calculations:(15)
a)   [F.sub.n] = [] + ([F.sub.fyma] - [F.sub.fym])
    [F.sub.n] = the net increase in fertilizer
    [] = fertilizer value of currently burnt biomass, if it
    was digested anaerobically instead.
    [F.sub.fyma] = fertilizer value of biomass currently composted as
    farmyard manure, if it was digested anaerobically.
    [F.sub.fym] = fertlizer value of biomass currently composted as
    farmyard manure.
b)   Surveys from 13 states during 1962-69 found that 72
    percent of total dung is collected on an average from
    urban and rural areas.   When this figure is combined with
    earlier calculations, we find that 92.1 MT of rural dung
    (dry weight) X 72 percent = 66.3 MT of dung (dry weight)
    that is actually used as manure in rural areas each year.
    An estimated 10 MT (dry weight) of a possible 34 MT of
    agricultural residues are added to this.  This produces a
    total of 76.3 MT of dung and agricultural residues that
    currently are being used for fertilizer in rural areas.
    The remaining 25.8 MT of dung and 24 MT of agricultural
    residues, or a total of 49.8 MT (dry weight), currently
    are consumed as fuel, assuming the same rate of collection
    and distribution as explained above.
c)   Using the calculations from (b) above and Table II, the
    values for [], [F.sub.fyma], and [F.sub.fym] are shown below.  Values
    are in MT:
                                 N         [P.sub.2][O.sub.5]      [K.sub.2.O]
                               _____      _______  _______
    []                   .847      .797     .498
    [F.sub.fyma]                1.297     1.221     .763
    [F.sub.fym]                  .763      .458     .916
d)   Therefore, the net increase in fertilizer due to digesting
    available organic material in biogas is approximately:
    [] + ([F.sub.fyma] - [F.sub.fym]) = [F.sub.n] (a)
    .847 + (1.297 - .763) = 1.381 MT of N.
    .797 + (1.221 - .458) = 1.560 MT of [P.sub.2][O.sub.5]
    .498 + (0.763 - .916) = .345 MT of [K.sub.2]O
In 1979-1980, 1.295 MT of N, .237 MT of P, and .473 MT of K
were imported at a cost of Rs 887.9 crores with additional subsidies
of Rs 320 crores.(16)  While our calculations show the
enormous potential of biogas slurry in meeting domestic fertilizer
needs, it must be noted that to organize such an effort
would be a massive task.  Manure would have to be collected from
very diffuse points and transported to farms as needed.  Fertilizer
requirements will increase dramatically as India's population
approaches one billion people shortly after 2000 A.D.,
including an increased demand for chemical fertilizers.  Organic
fertilizers from the slurry of biogas systems could certainly
contribute to fertilizer supply needs.  Our analysis is probably
somewhat understated in that, as additional residues will be
available from increased crop production, a potential increase
in cattle population or improved cattle diet will mean more
dung.   Also, a variety of organic materials such as water hyacinth,
forest litter, and other under-utilized biomass could
all be digested, increasing the fertilizer derived from biogas
The above discussion is intended only to illustrate the order
of magnitude of the potential impact of large-scale utilization
of biogas systems.  Much of the data used were aggregated from
small and often inaccurate sample surveys, causing considerable
margins of error.  This problem will be discussed further at the
end of this section.
Additional insight into the potential contribution of biogas
systems can be obtained from recent projections of rural energy
demand.   Commercial and noncommercial energy demand, based on
the Report of the Working Group on Energy Policy, is shown in
Table I-3.
This data is the basis of the Reference Level Forecast of the
study, an extrapolation of current trends.  It is interesting to
note that the household sector (90 percent of India's households
are in rural areas) is assumed to account for almost all
noncommercial fuel consumption throughout this period, except
for 50 MTCR of firewood, agricultural residues, and bagasse
that are used in industry.  The Working Group also suggests that
noncommercial fuels, as a percentage of total household demand,
will gradually decline from the current 83.9 percent to 49.7
percent, and that the percentage of the total noncommercial
fuel demand in all of India will drop from 43.5 percent to 11.5
                               Table I-3
                        Reference Level Forecast
                      Energy Demand (1976 - 2000)
                      In Household and All-India
         In Millions of Tonnes of Coal Replacement (MTCR)(17)
                            Commercial Fuels
                         MTCR (percent of total)
                         1976               1983               2000
                     _____________     ______________     ______________
Household              37.4 (16.1)        51.6 (20.2)        165.5 (50.3)
All-India             252.7 (56.5)       390.2 (65.7)      1,261.3 (88.5)
                         Non-Commercial Fuels
                      MTCR (percent of total)
                         1976               1983               2000
                     _____________     ______________     ______________
Household              194.6 (83.9)       204.1 (79.8)       163.5 (49.7)
All-India              194.6 (43.5)       204.1 (34.3)       163.5 (11.5)
Note:   Indian coal contains 5,000 kcal/kg.
The Working Group does not view this situation as desirable,
and offers an Optimal Level Forecast based on a series of policy
recommendations.   This is shown in Table I-4.
For this optimistic projection to be realized (assuming total
demand remains the same), commercial fuels will need to be
substituted increasingly by noncommercial fuels.  By 1983, noncommercial
demand for all-India must increase by 1.3 MTCR over
present projections.
                                 Table I-4
                         Optimal Level Forecast(*)
                        Energy Demand (1982 - 2000)
                     For Household Sector and All-India
            In Millions of Tonnes of Coal Replacement (MTCR)(18)
                              Commercial Fuels
                           MTCR (percent of total)
                               1983                      2000
                           _____________            ______________
Households                   51.6 (20.0)(*)            134.3 (41.0)(*)
All-India                   388.9 (65.4)             1,017.8 (71.3)
                              Non-Commercial Fuels
                             MTCR (percent of total)
                               1983                      2000
                           _____________            ______________
Households                   204.1 (80.0)             194.7 (59.0)
All-India                    205.4 (34.6)(*)           407.0 (28.7)(*)
(*) Note:  The author has calculated commercial fuel demand for
           households and non-commercial fuel demand for All-India
           on the assumption that the Reference Level Forecast
           total demand for each category remains constant.
           A relative increase in demand for commercial fuels
           would cause a relative decrease in demand for non-commercial
           fuels.   Conservation measures would reduce
           overall demand, and thus reduce the amount of non-commercial
           fuels needed to bridge the gap between
           supply and demand.
           The actual figures are not included in the Report of
           the Working Group on Energy Policy.
By the year 2000, the household noncommercial fuel demand must
increase by 31.2 MTCR, and noncommercial fuel demand in all of
India must increase by 273.5 MTCR if commercial fuel consumption
is to remain at the level suggested in the Optimal
Forecast (without additional conservation).
Though these projections can be criticized for relying on
suspect sample data(19) or questionable assumptions,(20) The Report
of the Working Group nonetheless shows clearly that an increase
in energy from noncommercial, renewable resources is a high
priority.   The report specifically describes biogas systems as
"the most promising alternative energy technology in the household
sector," although it does not minimize some of the problems
associated with the technology.(21)
The optimal level forecast for irrigation and lighting (based
on a series of recommended conservation measures) is shown in
Table I-5.
                               Table I-5
    Electricity and Diesel Demand:   Irrigation and Rural Lighting
                             (1976 - 2000)(22)
                               1978            1983            2000         1978-2000 
Diesel                           2.6             4.6             6.6          + 4.0
(billion liters)
Electricity                     14.2            16.0            28.0          +13.8
(billions of KWH)
ELECTRICITY                      4.4           10.7            32.2           +21.5
(billions of KWH)
(With rural                    (3.7)           (9.6)          (29.0)        (+25.3)
households at
90 percent of total)
                              ________       _________      _________      __________
Total Rural                    17.9            25.6            57.0          +39.1
Electric Demand
(billions of KWH)
NOTE:   Electric pumps consume approximately 3,000 KWH/year/
       pumpset (at about 5 HP/pumpset).
       Diesel pumps consume approximately 1,000 liters (.8
       tonnes) of diesel fuel/year/pumpset.
In 1978-1979, an estimated 360,000 electric pumpsets and 2.7
million diesel pumps were used for irrigation.  Future growth is
projected to increase to 5.4 million electric pumpsets and 3.3
million diesel pumps by 1983.  The estimated ultimate potential
of 15.4 million energized wells optimistically is reached by
the year 2000, when there will be 11 million electric pumpsets
and 4.4 million diesel pumps in operation.  Animal-power lifting
devices are expected to decline from around 3.7 million in 1978
to 660,000 by the year 2000.(23)
As shown in Table I-5, the total increase in projected diesel
fuel demand for irrigation between 1978-2000 is 4 billion
liters or 16 billion BHP-hrs, since .25 liters of diesel generate
1 BHP-hr.  For the same period, rural electricity demand
(irrigation and household lighting) is expected to increase by
39.1 billion kwh.  Modified diesel engines can run on a mixture
of 80 percent biogas and 20 percent diesel.  Since .25 liters of
diesel = 1 BHP, .05 liters can be mixed with .42 [m.sub.3] of biogas
to generate the same power.  Using a conversion factor of 1 BHP
= .74 kwh, .07 liters of diesel mixed with .56 [m.sub.3] of biogas
will generate 1 kwh.(24)  Therefore, the 16 billion BHP-hrs required
by the year 2000 to run diesel pumpsets could be supplied
by a little over 6.7 billion [m.sub.3] of biogas and .8 billion
liters of diesel fuel.  Alternatively, the 39.1 billion kwh
required for rural electricity needs could be supplied by 21.9
billion [m.sup.3] of biogas and 2.74 billion liters of diesel fuel.
We have previously calculated that at least 25 billion [m.sub.3] of
biogas is potentially available from current patterns of biomass
use.   If, and it is a big "if", an alternative cooking fuel
could be supplied to those areas that presently rely on dung
and plant wastes, perhaps with fuelwood plantations, this biomass
could be shifted toward meeting a large share of increased
demand for commercial fuels in rural areas.  Since food production
and cattle population will have to increase to keep pace
with population growth, the amount of available biomass, and
hence biogas, will expand similarly.  The total increase in
rural commercial fuel demand could be met by a mix of 28.6
billion [m.sub.3] of biogas and 3.6 billion liters of diesel, which is
less than the 4 billion liters projected in Table I-5.  Such
a substitution seems well within the range of technical
Some of the economic aspects of substituting biogas for diesel
and electricity are discussed in section VI.  In many villages,
the costs of connection to the nearest central grid are prohibitive
even if the load were increased to include lighting,
pumpsets, etc.(25)  For some areas, biogas may represent the only
viable technology, whether or not the gas is burned directly or
converted to electricity.  As the Working Group notes, despite
the fact that roughly half of India's villages are electrified,
population increases have kept the percentage of total households
that are electrified relatively constant at 14 percent.
Within "electrified" villages, only 10-14 percent of the houses
obtain electricity for household applications.  Only 5 percent
of rural houses use electricity for lighting because rural
family incomes cannot support the high installation cost of
As an alternative, a benefit of a large-scale biogas program
could be to free up the millions of tonnes of firewood that are
consumed annually for cooking.  Using the Working Group on
Energy's norm of 1 MT of firewood (all types) = .95 MTCR, this
represents almost 66.8 MTCR, which is over 30 percent of the
increased demand for noncommercial fuels, or 10 percent of the
increased demand for commercial fuels in the optimal level
forecast for the year 2000.  While the actual use of this vast
amount of energy would depend on the economic, social, and
managerial constraints associated with various thermal conversion
processes, the possibilities for converting this energy
into electricity, gas, or pyrolytic oil deserve serious
Before biogas could be used as a substitute for commercial
fuels, a number of complex energy demand, investment, and
development issues would need to be analyzed carefully.  Such an
analysis is far beyond the scope of this study.  Nevertheless,
it is in India's interest to raise these questions since there
are many different energy supply mixes that are technically
possible, given India's resources.  The preceeding discussion is
intended only to show the magnitude of the potential
contribution that biogas systems could make to India's energy
and fertilizer needs.
A number of technical, political, and organizational problems
must be solved before a large-scale biogas program can be
undertaken.   The remainder of this study is devoted to exploring
these problems in some detail.
             II.   An Overview of Biogas Systems
Most biogas systems consist of a basic series of operations,
which is described briefly in this chapter.  There may be certain
variations or additions to this basic schematic design,
especially if the system is integrated with other "biotechnologies,"
such as algae ponds or pisciculture, or if additional
uses can be found for carbon dioxide ([CO.sub.2]) that is present
in biogas.  A brief description of the different aspects of a
biogas system is necessary before discussing the economic and
social dimensions of the technology.
Almost any organic, predominantly cellulosic material can be
used as a feed material for a biogas system.  In India, the
Hindi name for these systems, "gobar" (dung) gas plants, is
imprecise.   This is shown by the following list of common
organic materials that may be used in gobar gas plants:(27)
     *  algae
     *  animal wastes
     *  crop residues
     *  forest litter
     *  garbage and kitchen wastes
     *  grass
     *  human wastes
     *  paper wastes
     *  seaweed
     *  spent waste from sugar cane refinery
     *  straw
     *  water hyacinth and other aquatic weeds
Table II-1 on the following page shows some laboratory yields
associated with different biomass.  It is important to remember
that the amount of gas produced from different kinds of biomass
depends on a number of variables.  The most important of these
include the temperature and the amount of time that the biomass
is retained in the digester, which is called the loading rate.
Unless stated otherwise, all biomass has been tested at 35 [degrees] C
and retained for a 35-day period.
Despite the obvious sanitation benefits of feeding human feces
into a biogas digester, this practice produces a per capita
daily gas yield of only about .025 [m.sup.3].  This means that the
excrement from perhaps 60 people would be needed to provide
enough gas for the cooking needs of a family of five people.   In
addition, excessive slurry dilution can result from uncontrolled
     Table II-1 Gas Yields for Selected Organic Materials(28)
   Material         Gas yield in [m.sup.3]/kg of volatile solids
   cattle dung                                    .20
   human feces                                    .45
   banana stems                                   .75
   water hyacinth                                 .79
   eucalyptus leaves                              .89
rinsing in a community latrine, since all the latrine
water will enter the digester.  Corrosive hydrogen sulfide ([H.sub.2]S)
is more prevalent in human waste than in animal dung.  This may
adversely affect engines run on the biogas unless the gas is
passed through iron filings for purification.  Nevertheless, the
role of human enteric pathogens in the communication of disease
is well established.  Therefore, latrines could be incorporated
into a biogas system, provided they are accepted by villagers,
affordable, not disruptive of the digestion process, and not
harmful to any engine operation.  Safe procedures for handling
both influent and effluent also must be developed.  More research
is needed to understand the effects of different combinations
of temperatures and retention times in killing harmful
pathogens that could remain in the digested slurry.
Water hyacinth is particularly appealing because it is not used
as animal fodder, and therefore does not present any "food or
fuel" choices.  In addition to its higher gas yield, water
hyacinth produces gas that appears to have a greater methane
content and more soil nutrients than digested dung.  However,
there are some drawbacks to using water hyacinth.  One is that
its water requirements are vast.  Through transpiration from its
leaves, hyacinth absorbs from three to seven times the amount
of water that would normally be lost to surface evaporation
from the water occupied by the hyacinth.  Water hyacinth also
can become a breeding ground for mosquitoes and snails, although
these can be controlled by introducing predator fish.(29)
There are certain annoyances associated with the use of this
and other plant materials.  Younger plants yield more gas than
older plants, which may necessitate greater discrimination in
the manner in which biomass is collected.  Plants may have to be
dried and shredded to ensure proper mixing, dilution, and
digestion.   It may often be necessary to add urine to maintain a
proper carbon to nitrogen (C/N) ratio.  There have been many
field reports of scum build-up, clogged inlet tanks, and toxicity
to methanogenic bacteria (due to the "shock" caused by the
introduction of different biomass materials).  However, these
reports are sketchy, and the problems could be due to improper
digester design or operation.  Water hyacinth is almost always
mixed with dung; there is little reliable field experience
using water hyacinth as the sole input, although this has
been done successfully in laboratories, as will be discussed
Several Indian research groups have been experimenting with
"bio-dung"--a fuel cake and/or biogas feed material made from
dried and partially composted organic matter of varying combinations.(30)
Excellent gas yields have been reported with this
still experimental idea, but documentation is insufficient.
Nonetheless, this practice of "partial digestion" of the
biomass in plastic bags seems similar to the 10-day "predigestion"
period observed in China, where organic material is composted
prior to batch loading in family digesters.(31)  The
Chinese report faster gas production if material is partially
digested.   The process probably reduces the [CO.sub.2] present in the
early phases of digestion by simply releasing it in the
atmosphere as the gas percolates up through the compost pits.
There are many advantages claimed by proponents of "bio-dung,"
such as its greater gas yield, higher calorific value, potential
for generating revenue as a saleable product, eradication
of harmful weeds, and making family-scale digesters affordable
to those who own fewer than three to four cattle.  There is
little evidence currently available to evaluate these
There has been a good deal of experimentation with the digestion
of organic materials in various combinations.  Regardless
of the biomass used, it must be loaded without being diluted
excessively with water.  Most researchers mix fresh dung and/or
sun-dried organic matter with water at roughly a 1:1 ratio.   If
the plant matter is still green or the cattle diet is rich in
straw, the ratio should be changed slightly to about 1:0.8.
Materials should have a C/N ratio of roughly 30:1 due to the
digestive requirements of methanogenic bacteria.  The relative
proportions of different material should be adjusted to
maintain this ratio.(32)
The inlet tank can become clogged when assorted feeds of different
sizes and composition materials are mixed.  Fibrous
material can be shredded to avoid this.  Different digester
designs, incorporating larger inlets, may alleviate this problem
Most Indian systems work best if the biomass and water are
mixed thoroughly in the inlet tank prior to injection into the
digester.   Many of these inlet tanks have a removable plug to
block the inlet pipe during mixing.  Alternatively, the Chinese
seem to use less water and spend less time mixing material.
This is perhaps due to their batch feeding process, which
eliminates the need to add slurry daily.(33)
Anaerobic digestion consists broadly of three phases:
1.   Enzymatic hydrolysis--where the fats, starches, and proteins
    contained in cellulosic biomass are broken down into simple
2.   Acid formation--where acid-forming bacteria break down
    simple compounds into acetic acids and volatile solids.
3.   Methane formation--where methanogenic bacteria digest these
    acids and solids and give off [CH.sub.4], [CO.sub.2], and traces of [H.sub.2]S.
Any remaining indigestible matter is found in either the
"supernatant" (the spent liquids from the original slurry) or
the "sludge" (the heavier spent solids).  These two products are
often described as "slurry" because the influent in most Indian
plants is diluted with water at about a 1:1 ratio to form a
relatively homogenous, liquid-like mixture.  In China, the
supernatant and sludge generally settle into separate layers in
either the digester itself or in the output tank, and are
removed separately by buckets that are lowered to different
During the first phase of digestion, a great deal Of [CO.sub.2] is
produced and pH drops off to roughly 6.2 (pH values of less
than 6.2 are toxic to the bacteria needed for digestion).  After
about ten days, pH begins to rise, stabilizing at between 7-8.
Temperatures below 15 [degrees] C (60 [degrees] F) significantly reduce gas production.
During the winter months, many family-scale biogas systems
in northern India reportedly produce only 20-40 percent of
their summer yields.  Similarly, Chinese plants often produce
almost no gas during winter, and more than half the annual
energy required for cooking must be provided by burning crop
residues directly.  However, the need for a backup source of
energy to supplement a biogas system can probably be eliminated
with some of the design modifications suggested in the next
section.   Higher temperatures generally increase gas production,
reduce retention time, and increase loading rates, once the
bacteria adjust to the warmer environment.  Mesophilic bacteria
favor temperatures near 35 [degrees] C (95 [degrees] F).  Thermophilic bacterial
strains are found in the 50-60 [degrees] C (122-140 [degrees] F) range.   The
addition of nitrogen-rich urine seems to aid in gas production
during winter, especially when it is combined with plant
wastes.   Digesting the wet straw flooring from cattle sheds, if
available, is a convenient way to add urine to the influent.
The microbial population of methanogenic bacteria will decrease
as slurry flows out from the digester.  These bacteria have a
doubling rate of roughly 40 hours.  However, this slow growth
rate can be overcome by greatly increasing the microbial population.
There has been informal discussion among experts about
a process, reportedly developed in Belgium, that uses a membrane
to retain the methanogenic bacteria inside the digester.
Gas yield per kg of biomass reportedly increases by a factor of
5-10 when the membrane is used.  If these claims can be documented,
and if the membrane is both affordable and durable, it
would be an important development.  There also is sketchy
evidence that methanogenic bacteria are pressure sensitive.
This might be a problem in some fixed dome systems, which can
generate pressure above a water column of 80-90 cm.  More
research is needed on this point.
The effect of animal diet on gas yield has received far less
attention than it deserves.  Cattle can be either well fed or
near starvation, depending on the income of a farmer and the
time of year.  Farmers often barely maintain their cattle until
just prior to plowing season, when the diet is increased to
fatten the cattle for work.  Obviously, the less an animal eats,
the less dung it produces.  The more cellulose, especially in
fibrous materials, that it eats, the greater the gas yield will
be.   More research is needed to determine the optimal diet for
cattle given their use as a source of milk, motive power, and
combustible energy (biogas), and also considering local resources,
available capital, and knowledge constraints.(35)  Even
without this research, however, it is clear that diet, grazing
habits, and costs of collection will greatly affect the net
available dung yield per animal.
Many statistics quoted in the literature simply may not apply
to a particular locale.  These include data on dung yield of
animals, gas yield of dung, temperature, the nature and nutrient
content of other materials digested, and the [CH.sub.4] content,
which can vary 50-70 percent for a given quantity of biogas,
depending on diet.  Inaccuracies usually manifest themselves in
an overestimation of gas availability and overall benefits.
Norms mentioned in numerous studies are useful guides to these
questions but cannot replace micro-analysis.
A great deal of research is furthering our understanding of the
microbiological aspects of biogas systems.(36)  If gas yield could
be increased and retention time reduced, production costs would
decrease, since a smaller volume of biomass per cubic meter of
gas would be required.  Some of the areas or research include
ways to increase the growth rate of methanogenic bacteria,
improve the digestibility of lignin, develop microbiological.
innoculins that would increase gas production, develop bacterial
strains that are less sensitive to cold weather, identify
micro-organisms involved in digestion, and separate acid-forming
and methanogenic bacteria.  As of the writing of this
study, there have been no major documented performance breakthroughs
achieved as a result of this research.
                  III.   Digester Designs
There are many ways to design biogas systems.  The designs
discussed in this study are by no means the only possibilities.
They either have been tested extensively or were in the midst
of serious research and development during the writing of this
study.   Groups attempting to develop their own systems should
use the illustrations in this section only as guides.  The
characteristics and costs of labor, construction materials,
land, etc., will vary according to local conditions and the end
uses of the system's gas and slurry.
The Khadi and Village Industries Commission (KVIC) design has
been developed over the past 15 years and is similar to the

53p18.gif (600x600)

majority of systems currently operating in India (see Figure III-1).(37)
As of 1981, KVIC claims to have built about 80,000 of
these systems, although there are no reliable data on how many
of the units are actually operating, temporarily shut down, or
nonfunctioning.   The KVIC system consists of a deep well and a
floating drum that usually is made of mild steel.  The system
collects the gas and keeps it at a relatively constant pressure.
As more gas is produced, the drum gas holder rises.  As
the gas is consumed, the drum falls.  Actual dimensions and
weight of the drum are functions of energy requirements.  A long
distribution pipeline that might necessitate greater pressure
to push gas through its length would require a heavier drum,
perhaps weighted with concrete or rocks.  Biomass slurry moves
through the digester because the greater height of the inlet
tank creates more hydrostatic pressure than the lower height of
the outlet tank.  A partition wall in the tank prevents fresh
material from "short circuiting" the digestion process by displacement
as it is poured into the inlet tank.  Only material
that has been thoroughly digested can flow up and over the
partition wall into the outlet tank.
Most KVIC systems are designed to retain each daily charge for
50 days, although this has been reduced to 35 days in newer
units.   The slurry should be agitated slightly to prevent any
chance of stratification.  This is accomplished by daily rotation
of the drum about its guide post for about 10 minutes.  In
Nepal, some gas holders have been painted to look like prayer
wheels.   They are turned during frequent religious ceremonies,
or "puja" (individual prayer).  The Nepali group, Development
and Consulting Services (DCS), Butwal, also has modified the
KVIC gas pipe connection.  It has attached an underground fixed
pipe to the guidepost, feeding gas through the guidepipe rather
than connnecting a flexible hose to the roof of the gas holder.

53p19.gif (600x600)

DCS uses a taper design for high water table areas (see Figure III-2)
and a straight design for low water table areas (see
Figure III-3).

53p20.gif (600x600)

KVIC systems are reliable if properly maintained, although drum
corrosion has historically been a major problem.  It appears
that the quality of steel manufactured in India may have
declined during the early 1960s.  There are anecdotes of
unpainted systems built before then that are still functioning.
Drums should be coated once a year with a rustproof bitumin
paint.   Oil can also be introduced into the top of the digester
slurry, effectively coating the steel drum as it rises and
KVIC designs of over 100 [m.sup.3] have been constructed for institutions
such as schools, dairies, and prisons.  Though construction
economies of scale exist for all digesters, the use of
mild steel accounts for 40 percent of the system cost.  KVIC
systems are relatively expensive.  The smallest family KVIC system
costs well over Rs 4,000 (US$500) to install.  KVIC has experimented
with a number of materials, including plastics, for
dome construction.  The Structural Engineering Research Center,
Rourkee, has done work with ferrocement, reducing costs somewhat.
Ferrocement gas holders become extremely heavy as their
scale increases, and they require proper curing and a fair
amount of manufacturing skill.  The curing process requires that
domes be either submerged in water for 14 days or else wrapped
in water-soaked cloth or jute sacks for 28 days.  This raises
questions about their use, or at least their fabrication, in
many villages.  KVIC would like to prefabricate both gas holders
and digester sections at regional centers and then transport
these out to villages.  This would create rural industry and
employment, and introduce quality control into the manufacturing
Dr. A.K.N. Reddy and his colleagues at the Cell for the Application
of Science and Technology to Rural Areas (ASTRA), and
the Indian Institute of Science, Bangalore, have modified the
KVIC design in several important ways.  The result is a shallower,
broader digester than the KVIC design.  Table III-1 shows
some statistical comparisons between the two designs.(38)
ASTRA also examined the retention time for a charge of biomass,
given Bangalore climatic conditions, and reduced the 50-day
retention period suggested by KVIC to 35 days.  It observed that
since almost 80 percent of the total amount of gas produced was
generated within the shorter time, the increase in digester
capacity necessary to more completely digest slurry did not
seem justified.  Further research on cutting down retention time
as a way to reduce system costs may suggest other design modifications.
The shorter the retention period, the less digester
volume (and hence, lower cost of construction) is required for
the storage of the same volume of organic material.  As shown in
Table III-I, the ASTRA unit, though almost 40 percent cheaper
than the KVIC unit, had a 14 percent increase in gas yield.  Its
improved performance needs to be monitored over time.(39)
                               Table III-1
                    Comparison of KVIC and ASTRA designs
                       for similar Biogas Plants(40)
                                        KVIC               ASTRA
Rated daily gas output                  5.66               5.66
Gas holder diameter (m)                 1.83               2.44
Gas holder height (m)                   1.22               0.61
Gas holder volume ([m.sup.3])           3.21               2.85
Digester diameter (m)                   1.98               2.59
Digester depth (m)                      4.88               2.44
Digester depth-diameter ratio           2.46               0.94
Digester volume ([m.sup.3])            15.02              12.85
Capital cost of plant (Rs)          8,100.00           4,765.00
Relative costs                        100.00              58.80
Daily loading (kg fresh dung)         150.00             150.00
Mean temperature (Celsius)             27.60             27.60
Daily gas yield ([m.sup.3]/day)  4.28 [+ or -] 0.47  4.39[+ or -] 0.60
Actual capacity/rated capacity         75.6%             86.4%
Gas yield (cm/g fresh dung)       28.5 [+ or -] 3.2   32.7 [+ or -] 4.0
Improvement in gas yield             --                  +14.2%
The ASTRA group conducted a series of tests on existing biogas
systems and found that there was uniform slurry temperature and
density throughout the digester,(41) and that the heat lost in
biogas systems occurs mainly through the gas holder roof.   It
also found that when the colder-temperature water was mixed
with dung to make slurry, the charge shocked the indigenous
bacteria and retarded gas production.  The result was a 40
percent or more reduction in gas yield.(42)
An important goal thus was to control the temperature of the
slurry.   This raised a number of problems:   maintaining the
slurry temperature at the 35 [degrees] C (95 [degrees] F) optimum; heating the
daily charge to minimize temperature loss due to colder ambient
temperatures; and providing insulation for the floating drum
gas holder.  ASTRA found an ingenious solution to all these
needs.   It installed a transparent tent-like solar collector on

53p23.gif (600x600)

top of an ASTRA floating drum gas holder (see Figure III-4).(43)
This was done by modifying the drum design so that its side
walls extended up beyond the holder roof, forming a container
in which to place water.  This water was drawn from the
collector, heated by the sun, and mixed with the daily charge
of dung.   Preliminary data from the 1979 Bangalore rainy season
showed an increase in gas yield of about 11 percent with this
solar heating system.  During this often cloudy period, the
temperature of the water in the collector was only 45 [degrees] C (112 [degrees] F)
compared with the 60 [degrees] C (140 [degrees] F) temperature recorded during the
summer months.  More work is needed to improve the cost and performance
of this solar heating method, but its potential for
reducing system costs seems promising, especially on a village
scale.   In addition, distilled water can be obtained by collecting
the condensate as it runs down the inclined collector roof.
The ASTRA group is constructing a 42.5 [m.sup.3] biogas system in Pura
village, Tumkur District, near Bangalore, that eventually will
incorporate ferrocement gas holders and solar heating systems,
enabling the group to evaluate its ideas in an actual village
context.   Dr. C. Gupta, Director of the TATA Energy Research
Center, Pondicherry, is constructing an ASTRA design biogas
system with a community latrine in Ladakh, Jammu and Kashmir
State, where the 3,600-meter altitude and chilly winter
temperatures will provide valuable data on the performance of
this design.  Most recently, ASTRA has reportedly constructed a
2.3 [m.sup.3] fixed dome plant for Rs 900 (US$112).  It may be possible
to reduce this cost further by experimenting with a compacted
earth pit that would be covered by a brick dome.  The costs of
constructing the brick digester would thereby be eliminated.
Such experiments are still quite recent and the data on performance
and durability are not yet available.  Parts of
Karnataka have large, brick-producing activities, and the easy
availability of inexpensive bricks may account partially for
this low cost.  Nevertheless, the potential exists for large
reductions in system costs, which could alter dramatically the
economics of biogas systems.
The Planning Research and Action Division (PRAD) of the State
Planning Institute, Lucknow, has been conducting biogas research
at its Gobar Gas Experimental Station, Ajitmal (near
Etawah), Uttar Pradesh, for more than 20 years.  PRAD constructed
the 80 [m.sup.3] community system in the village of Fateh Singh-Ka-Purva,
which will be discussed later in this study.  After several
years of experimentation with designs modified from the
fixed dome systems popular in the People's Republic of China,
PRAD developed the "Janata" fixed-dome plant.(44)
The PRAD design has several advantages.  A Janata plant system
can be built for about two-thirds the cost of a KVIC system of
similar capacity, depending on local conditions, prices, and
the availability of construction materials.  The magnitude of
savings due to the all-brick Janata design may diminish with
increased capacity, but there is little data regarding large
fixed-dome plants.  One of the key features of the Janata and
other fixed-dome designs is that inlet and outlet tank volumes
are calculated to ensure minimum and maximum gas pressures due
to the volumes displaced by the changing volumes of both gas
and slurry inside the system.
Janata designs are relatively easy to construct and maintain
because they have no moving parts and because corrosion is not
a problem.  One drawback is that Janata plants may require periodic
cleaning due to scum build-up.  As gas pressure increases
in a fixed volume, the pressure pushes some of the slurry out
of the digester and back into both the inlet and outlet tanks,
causing the slurry level in each tank to rise.  As gas is consumed,
the slurry level in the tanks drops and slurry flows

53p250.gif (600x600)

back into the digester itself (See Figures III-5a through III-5d).
Such movement probably acts as helpful agitation, but
the motion may also cause heavier material to settle on the
bottom of the digester.  The result then is that only the supernatant
flows through the system.  Such buildup has been reported
occasionally, and may result in a gradual accumulation of
sludge that could cause clogging.
The more serious problem is posed by the heterogeneous nature
of even the most well-mixed influent.  Lighter material can form
a layer of scum that remains unbroken precisely because the
plants are designed to prevent the slurry level from descending
below the top of the inlet and outlet tank openings in the
digester, which might allow gas to escape through the tanks.
This problem of scum build-up may be more serious in large-scale
plants, and may require the installation of stirring
The digester must be cleaned if build-up does occur.  Someone
must descend into the unit through the outlet tank and scrape
out the sludge.  The Janata plant has no sealed manhole cover in
the dome.  This differs from Chinese plants, for which sludge
removal is assumed to be a regular part of normal operation.
With the Janata plant, extreme caution must be used when entering
the digester since concentrated [CH.sub.4] is highly toxic and
potentially explosive.  The Chinese often test this by lowering
a caged bird or small animal into an emptied digester, exposing
it to the gases for some time, and then descending only if the
animal lives.
More research is needed on the kinetics and fluid dynamics of
fixed-dome plants.  The ASTRA observation of homogeneous slurry
density in the KVIC unit would seem to conflict with some field
reports, although poor maintenance and lack of thorough mixing
may account for such discrepancies.
An important advantage of Janata plants is that their required
construction materials are usually available locally.  Lime and
mortar can substitute for concrete.  Neither steel (which often
is scarce) nor ferrocement are needed, which reduces dependence
on often unreliable outside manufacturing firms and suppliers.
The dome of the Janata plant does require a good deal of
skilled masonry, including several layers of plastering, to
ensure a leak-proof surface.  Many early plants leaked badly.
PRAD reports this is no longer a problem due to extensive
construction experience and the fact than it has trained many
local masons in Uttar Pradesh who can competently construct
such units.
Although PRAD recommends constructing a raised platform to
support the earthen mound that serves as the form for the construction
of the brick dome, the Chinese build brick domes with
little or no support scaffolding.  It is difficult to learn this
technique unless one visits a construction team in China.   The
few manuals that exist are inadequate in explaining the construction
method, often omitting details such as the angle at
which bricks should be laid to form the correct arc for the
dome, or the number of rings required for bricks of unknown
Using some PRAD diagrams and A Chinese Biogas Manual, translated
by the Intermediate Technology Development Group (London,
1980), the author directed the construction of a modified 2 [m.sup.3]
Janata plant to be used as an experimental digester at the
Indian Institute of Technology, Madras.  A free-standing dome
was successfully constructed, but the process took three days
and required vigilant monitoring of cracks that occasionally
began to spread around different areas of the brick rings that
formed the dome.  The safety of masons working under the emerging
dome was cause for some concern.  The weight of the partially
formed arc sections easily could have proven fatal if someone
had been caught underneath a collapsing section.  It also
was difficult to set the bricks at a proper angle.  The dome
emerged somewhat misshapen, despite the use of a two-pole system
in which one pole defined the vertical axis and the other,
equal to the radius of a sphere formed by "extending" the dome,
pivoted about a nail.  By rotating the vertical pole 360 [degrees] and
lining up each brick ring with the angle formed by pivoting the
"radius" pole between 45 [degrees] and 135 [degrees] (off the horizontal), the
correct dome arc, and hence each brick's proper angle, should
have been readily apparent.  However, due to the irregular surface
of the bricks, the varying amounts of concrete applied to
the bricks, and the reluctance of the masons, for whatever
reason, to use the device frequently, the dome construction
became a matter of educated guesswork.
Given the short time many of the Janata systems have been
operating, the possibility still exists that micro-cracks may
develop in the dome over several years.  The Center for Science
for Villages, Wardha, has covered the top of its fixed-dome
plants with water so that any leaks will be visible as bubbles.
This idea could be further modified to incorporate an ASTRA
type solar collector to produce warm water for hot charging.
However, one of the additional advantages of the fixed-dome
designs is that they are largely underground.  This frees the
surface land area for alternative use.  Improved system performance
due to solar heating must be evaluated against other
possible uses of the land.
Fixed-dome plants release stored gas at pressures as high as 90
cm (36") of water column.  As gas is consumed, and in spite of
the changing slurry level, pressures do drop.  The amount of gas
inside the dome at any time can be estimated crudely by measuring
changes in the slurry level in the inlet and outlet tank
(as long as the daily charge has settled in the digester).
There is some concern that flame temperatures drop with lower
pressures, increasing cooking time and gas consumption.  However,
there seems to be little complaint from individual users
on this point.  Minimizing gas consumption during cooking can be
of great importance in a village system that requires gas for
uses other than cooking.  There are few data on the economic and
thermodynamic efficiencies of diesel or petrol engines or of
generators powered by a fixed-dome system.  Presumably, more
diesel would be consumed as pressure drops.  Gas pressure regulators
have been discussed periodically as a way to alleviate
this problem.  Regulators can ensure that enough pressure is
maintained throughout a distribution system, and that occasional
high pressure will not blow out valves or pipe joints.  Work
is now under way in Sri Lanka near the University of Peredeniya,
in Uttar Pradesh, and in Bihar on fixed-dome plants as
large as 50 [m.sup.3].  Plants of this size have been reported in
China, but little information is available to confirm this.   It
remains to be seen if cost reductions observed in small-scale,
fixed-dome plants will be repeated or even improved with increased
scale.   Constructing large domes from bricks, or even
from ferrocement, may prove difficult and/or expensive since
their performance and durability remain a matter of speculation.
Variations on the fixed-dome design have been reported in
Taiwan, where heavy gauge collapsible Hypalon/Neoprene bags
have been used as digesters.(45) The Sri A.M.M. Murrugappa
Chettiar Research Center (MCRC), Madras, has developed a brick
digester with a high-density polyethelene gas holder supported

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by a geodesic frame (see Figure III-6).  The frame is bolted to
the digester walls, and the plastic gas holder is retained by a
water seal.  The MCRC plant is still being tested in several
Tamil villages and few performance data are available.   The
plant is less expensive than the PRAD Janata design and has the
advantage of being easily and quickly installed.  However, major
questions remain concerning this design's durability and safety.
Only small-scale systems have been constructed, although
larger systems are planned.(46)
Development and Consulting Services (DCS) of the Butwal Technical
Institute, Butwal, Nepal, has begun field testing a horizontal
plug-flow digester design based on the work of Dr.
William Jewell of Cornell University (USA).  A long, shallow,
horizontal system night require less water, be less susceptible
to scum formation and clogging, and foster greater gas production.
A plug-flow system should be easier to clean, and would
require less excavation, helping to reduce costs.  This system
has great promise; a prototype should be developed within a
The Jyoti Solar Energy Institute, Vallabh Vidynagar, Gujarat
(near Anand), has done some interesting design work in conjunction
with the research on agricultural residues discussed
earlier.   JSEI researchers found that a scum layer was forming
in experimental digesters that were fed with banana stems,
water hyacinth, and eucalyptus leaves.  This layer gradually
reduced gas production to almost zero.  The researchers concluded
that the scum layer formed because the fresh biomass contained
a good deal of oxygen between its cell walls.  Since the
shredded sections were lighter than the water they displaced,
the biomass tended to float to the surface of the slurry.  During
experimental batch feeding, this scum layer was observed to
sink gradually to the digester floor as digestion progressed.
The scum layer that has troubled many of the digesters used for
agricultural residues seems to form when fresh biomass, entering
at the bottom of the digester, pushes up against heavier,
older biomass that is settling toward the digester floor.  The
lighter biomass causes the heavier layer to rise, creating the
thick scum layer.  JSEI engineers devised an ingenious system of
loading fresh biomass through the top of the gas holder to the
surface of the slurry by means of a plunger arrangement (see

53p31.gif (600x600)

Figure III-7).  This ensures that the heavier, partially digested
material settles to the digester floor unimpeded by the
lighter biomass.   The JSEI innovation could be an important
breakthrough in the use of agricultural and forest residues in
biogas systems.  In addition to solving the problem of scum
build-up, the JSEI technique also seems to eliminate the
necessity of excessive shredding or drying of residues, making
the handling of these materials far less cumbersome and time-consuming.
Biomass is merely chopped into 2-3 cm (.75-1.25")
squares and then is pushed into the digester through a cylindrical
tube inserted into the floating gas holder.  The tube is
always in contact with the slurry, even with the dome at
maximum height, so that no gas can escape.
There remain a number of questions concerning the relative performance
of fixed-dome plants versus floating drum plants.
Conflicting data have been reported concerning equipment life,
material durability, gas production, delivered gas pressure,
and installation and maintenance costs.  The Department of
Science and Technology has established five regional testing
centers where different designs of similar capacity are being
monitored under symmetrical, controlled conditions in different
agro-climatic regions.  One such station visited by the author,
in Gandhigram, Tamil Nadu, appears to have insufficient
resources to assess accurately the performance of the different
biogas systems that have been constructed.  More rigorous comparative
research on fixed-dome plants is needed, especially
after further design improvements, such as those done by ASTRA,
are completed.  The effects of agitation, digester wall protrusions,
and partition walls to improve gas yield need to be
analyzed in different digester designs.  It is not yet clear if
the cost advantages of fixed-dome digesters outweigh the performance
advantages of floating-drum digesters.  This may be a
function of the uses of the gas in a particular village, which
determines the relative importance of providing gas at a
constant pressure and the effectiveness and cost of pressure
regulators currently under development.  More research is needed
before any conclusions can be made.
There are numerous experimental digesters with modifications of
the designs described in the preceeding discussion.  MCRC is
planning to link its biogas plants with other biotechnology
projects, such as pisciculture, algae growth, and organic
farming.   The Indian Institute of Technology - Delhi Center for
Rural Development and Appropriate Technology is developing a
system that will grow algae in the supernatant of a fixed-dome
system.   It will recycle the algae to supplement the daily raw
material charge.  The system will provide fertilizer, gas,
oxygenated water for irrigation, and animal nutrients such as
single cell proteins for fodder.(48)  The idea is to generate the
maximum yield per unit of local resources.  Integrated systems
have a great deal of potential, although their often elegant
simplicity requires a great deal of skilled operation and
effective maintenance.
                   IV.   System Operation
The appropriate role of a biogas system in producing heat,
light, refrigeration, and motive power can be determined after
end-use energy requirements over time have been assessed carefully,
including any anticipated demand from population growth.
The system's capacity should be based on a careful analysis of
costs, local climate and soil conditions, and the net availability
of biomass.  This latter consideration must account for
competing uses of crop wastes and dung, animal diet, grazing
habits, difficulty of biomass collection, and the availability
of labor.  Also, the probabilities of the survey data remaining
constant over time must be assessed.
Many family-sized systems have been designed with insufficient
capacity to produce gas when it is needed at different times
during the day or year.  In India's colder northern climates,
the drop in gas production during winter often has been underestimated.
Great care should be exercised in preparing plant
feasibility studies so that different contingencies can be
accommodated without disrupting the operation of the system.
For example, farmers often sell cattle during droughts (if the
cattle survive), and this obviously reduces dung availability.
Baseline surveys of available biomass can be distorted if conducted
during periods of exceptionally good harvests or failed
It probably is wise to build two or more medium-size plants in
a village rather than one large plant, even though the total
cost may increase.  If problems or maintenance force a temporary
shutdown in one of the digesters, the entire system will not be
disrupted.   If small-scale, fixed-dome system costs call be reduced
to around Rs 400-500 (US$50-62), which does not seem
impossible, clusters of small systems might be a more cost-effective
way to provide energy than one large system.  Some of
the complexities of planning village energy systems are discussed
in the following section on the economic analysis of
biogas systems.(49)
Biogas plants require certain care during their initial starting
up or "charging."  If a digester contains a partition wall,
slurry must be added from both the inlet and outlet tanks to
This chapter presents certain points that are not usually
covered in discussions about biogas systems.  The author recommends
John Finlay's Operation and Maintenance of Gobar Gas
Plants[N] (1978) for a more complete description of how biogas
systems operate.
equalize pressure and prevent collapse of the wall.  While not
essential, introducing either composted manure or digested
slurry as seed material to the digester will speed up the
initial charging.  There is some disagreement over how best to
start up a plant.  One suggestion is to fill the digester as
rapidly as possible until the outlet tank begins to overflow,(50)
ensuring that the seed material is twice the volume of the
fresh biomass initially fed into the system.  Another is to
increase gradually over a three-week period the amount of biomass
mass introduced daily to the system.(51)  The inlet and outlet
tanks are then covered and digestion begins.
The plant should begin producing gas within 7-20 days, depending
on temperature, agitation, etc.  This initial gas is largely
[CO.sub.2] and should be released into the atmosphere; it will burn
poorly, if at all.  This step may have to be repeated.  Within a
month after charging, however, the system usually will have
developed a kind of critical mass of bacteria that is stable
enough to digest the daily biomass charge and produce gas.
Care should be taken to ensure that the biomass fed into the
system is relatively free from sand, gravel, and coarse fibers.
Many inlet tanks have a floor that slopes away from the opening
through which material flows into the digester.  The opening is
blocked during slurry mixing and the slurry is allowed to
settle for several minutes.  The plug is then removed and, as
the slurry drains into the digester, heavier sediments and foreign
matter collect at the lower end of the sloped inlet tank
floor.   This material can be removed after the slurry has
drained into the digester.  Material should be mixed thoroughly.
Shredders, screens, and mixing devices may be required for
village scale systems that handle a large amount of different
raw materials.  These precautions are recommended to reduce the
chances of the digester becoming clogged in either the inlet or
outlet tanks, or of having a scum layer form in the digester
itself.   More research is needed to understand the sensitivity
of biogas systems to variations in the biomass charge.  Similarly,
ideal rates of loading different materials at different
temperatures need to be determined.  Many of the guidelines for
operating biogas systems are based on trial and error observation
in the field.  The systems work, but their efficiency could
be increased and their costs reduced.
Systems should be built in a sunny area to take advantage of
solar radiation.  They should be at least 5-10 meters from a
source of drinking water sources, especially if human wastes
are used.  This is particularly important with large-scale systems,
which could represent concentrated sources of enteric
(intestinal) pathogens if they leak.  Adequate space should be
provided for raw material and water-mixing as well as for
slurry handling and storage.  Land and water requirements are a
critical and often underemphasized part of a biogas system.
Care must be taken to minimize water condensation in the gas
lines (possibly by including water traps), isolate sparks and
flames from the gas lines (by including flame traps), and prevent
pipe freezing in winter.  Provision must be made for frequent
inspection and maintenance of the system (including pipelines).
There also must be proper handling of the slurry to
conserve nutrients and minimize contact with pathogens in both
the influent and effluent.
If a biogas system is not performing as it should, the following
trouble-shooting sequence is suggested.(52)
1.   Check temperature of the influent mixture.  Sudden cooling of
    the slurry in the digester can impede microbiological digestion.
    Temperature variations should be kept to a minimum.
2.   Check loading rate of organic materials.  Overloading will
    cause material to flow out of the digester before the slurry
    has been digested.
3.   Check pH levels, which may drop below the 6.0-7.0 minimum.
    Add lime to increase the pH level, if necessary.
4.   Check for toxic material in the influent, and alter the composition
    of materials - mixed in the slurry.
Whenever daily feeding procedures are altered, the change
should be introduced gradually so that the microbial population
has time to adjust to the new environment.
             V.   Gas Distribution and Use
Gas distribution systems can cost from several hundred rupees
for a family system to as much as three/fourths the total cost
of a village scale digester (exclusive of pumpsets, engines,
generators, etc.).  Distribution costs can offset the scale
economies of larger digesters.  The distribution system in a
particular village will be determined by local conditions,
e.g., the distance between the points to which the gas must be
distributed (houses, pumpsets, or industries), the availability
of organic material, the difficulty of collection, and the
availability and cost of construction materials.
Because the gas is usually released from a floating drum holder
at a pressure of less than 20 cm of water column, the total
length of the distribution pipeline is probably limited to less
than 2 kilometers unless booster pumps are used, which increases
costs.   As delivery pressure decreases with pipeline
distance, the flame velocity gradually becomes too low to support
a stable flame.  Similarly, pumpsets for biogas that are
too far from the digester will require either an expensive
pipeline, a gas storage vessel/bag of some sort, or possible
conversion of the biogas to electricity.
Many different materials have been used in constructing pipelines,
such as GI pipe and PVC or HDP plastics.  It would seem
possible to use clay or earthen pipe as well.  Problems of gas
leaks, durability, and rodent damage vary with material characteristics
and care in construction.  Generally, plastic pipes
with a diameter greater than 35 mm seem best for cost optimization,
ease of construction, and favorable friction characteristics
to aid in gas flow.(53)  The availability of large quantities
of plastic piping may be a problem in certain locales.
One way to reduce the cost of pipelines might be to use the
same pipeline for delivering drinking or irrigation water as
well as gas.(54)  Water condensation in the pipeline would have to
be monitored carefully, as would any possible health hazards.
There are several descriptive accounts from China and Sri Lanka
of using bags to store and transport gas to run pumpsets and
tractors, and possibly to meet household cooking and lighting
needs.(55)   Kirloskar Oil Engines, Limited, is experimenting with
a rayon-coated rubber bag that has enough capacity to power a
5 hp pumpset for two hours.  It would cost approximately Rs 500
(US$40).   The general problem with such bags is that they must
be large enough to enable the gas to be released at the
10-12 cm water column pressure that is required for stove or
engine use.  Unless compressed in some way, a bag to provide
enough gas for the daily cooking and gas requirements for a
single family would have to be almost as big as the hut to
which it was attached.  In addition, the safety and durability
of such a system are debatable, given the rigors of village use
and the susceptability of such a system to vandalism.  Despite
the presence of [CO.sub.2] in biogas, puncturing a bag in the vicinity
of a flame could cause a large fire.  The danger is magnified if
the gas is purified by bubbling it through time to increase its
calorific value.
Nonetheless, a centralized delivery scheme where a few "regional"
pipelines are laid near clusters of huts, and from which
individual consumers fill their own storage bags, might have
certain advantages.  It may ultimately be cheaper than a full-scale
pipeline system.  It could expand easily if demand increased,
and would free families from being restricted to using
gas only during certain times of the day.  Most community systems
have several uses for gas and deliver gas only during
fixed times of peak demand, especially during morning and
evening cooking periods.  This staggered delivery is designed to
minimize gas waste, but can be inconvenient for villagers, who
occasionally have to work during the time gas is delivered in
their area.(56)  A decentralized "gas bag" system might facilitate
plant management and the easy monitoring of gas consumption.   It
might also allow for more efficient use of the gas.  There are
problems with this concept, but it has not yet received adequate
attention from biogas system designers.
The costs of pressurized biogas cylinders, similar to Liquid
Propane Gas (LPG), seem prohibitive.  Biogas can only be liquified
at -83 [degrees] C (-117 [degrees] F) and at a pressure of approximately 3.2
meters of water column.  Reddy has estimated that such a gas
cylinder system could almost double the cost of a pipeline in
Pura village.(57)  It is doubtful that individual families would
have sufficient capital to purchase cylinders (Rs 300-700/cylinder).
However, this concept should not be completely dismissed.
The revenue-generating potential of a large-scale
biomass system might justify an investment in a pressurized gas
cylinder system.  The compressor itself could be powered by the
biogas system.
Using biogas for cooking is more complicated than the literature
suggests.   KVIC (1980), Finlay (1978), National Academy of
Sciences (1977), Bhatia (1977), the Indian Council of Scientific
and Industrial Research (1976), and Parikh and Parikh
(1979) all suggest that gas requirements for cooking vary between
0.2 and 0.4 [m.sub.3]/person/day, although some anecdotal field
reports suggest that these figures may be high.(58)
The difficulty in establishing norms for gas required for cooking
is due to our scanty knowledge of rural cooking habits.  The
key to formulating cooking norms is to determine the usable or
net energy used by a family to prepare meals.  There are several
levels of analysis needed to generalize about net available
cooking energy.  Diet varies regionally according to climate,
custom, income, etc.  Even the quality (calorific value) of
identical fuel sources, such as firewood, varies regionally.
Finally, the efficiencies of stoves (often a group of stones),
and consequently the thermal efficiencies of different fuels,
are also highly variable.
A detailed investigation of these variables would begin to shed
some light on village cooking needs.  These are more difficult
to determine than the cooking needs of a wealthier farmer, who
is the most likely consumer of a family-sized biogas plant, and
on whom data do exist.  At the moment, there is no accurate way
to generalize about the gas required for village cooking.  KVIC
did attempt to generate data on the calorific value, thermal
efficiency, and "effective heat" of different fuels,(59) but no
description of its methodology is included in its report.  It
also assigned calorific values of biogas and wood, which conflict
with other analyses, thus leaving KVIC information open
to question.
Gas requirements for cooking can affect significantly the performance
and economic viability of a village system, depending
on competing uses for the gas.  This is especially true if non-cooking
uses of biogas are a source of revenue.  More research
and development are needed on cooking burners, stoves, and
cooking vessels (and on their heat conducting properties),
which collectively affect the efficiency of gas consumption.
The relative system efficiencies of metal and terracotta cookware
need to be analyzed.  Though metal is a better conductor of
heat, it also cools faster.  Terracotta vessels take longer to
heat yet they retain their heat.  Rice cooked in terracotta
vessels often is cooked only until half-done.  The vessel is
then removed from the fire, and the remainder of the cooking is
done with the heat that radiates from the walls of the terracotta
vessel.   This is why both energy consumption and cooking
costs need to be analyzed with respect to cooking systems,
i.e., the fabrication of all utensils, their collective thermal
properties, the costs of the various components (energy source,
stove, vessel) over their useful lives, and the nature of the
foods or liquids being heated.
The Gas Crafters' iron burner recommended by KVIC costs Rs 100.
Though "rated" at 60 percent efficiency, there have been complaints
about its air valve becoming clogged with fat and oil,
and that not all cooking vessels rest upon it equally well.
Developing and Consulting Services, Butwal, Nepal, claims to
have both improved this design and reduced its cost to Rs 80.(60)
There have been other attempts by the Gandhigram Trust and PRAD
to develop simple ceramic burners for as little as Rs 20, but
these are still experimental and little is known about their
performance or durability.  There are many photographs of a
variety of ceramic, bamboo, and stone-filled tin can burner
designs from China,(61) but again, no performance, durability, or
cost data exist.  The stove used for cooking with biogas may
itself have to be modified to achieve maximum efficiency.  The
Chinese often seem to set their cooking vessels on top of simple
burners in deep stoves that surround the vessels, thereby
using heat more efficiently.(62)
Social or cultural factors must be considered when designing a
distribution system.  The flame properties of biogas make burners
difficult to light unless a cooking vessel is resting on
the burner prior to lighting the gas.  This can conflict with
certain religious ceremonies that reverse the procedure as part
of the need to show reverence toward fire.(63)  Village cooking
requirements may be significantly affected by season.  In many
areas, when labor demand increases during harvesting and planting,
groups of workers are fed at staggered times throughout
the day.   During these peak times, stoves often are kept hot all
day for as long as two months of the year.  Such increases in
cooking energy requirements need to be studied by anyone involved
with the establishment of a village system.
The decision to use gas directly for lighting gas lamps, as
opposed to running a diesel generator to produce electricity
for electric lights, depends on the local demand for electricity.
Ghate found that while electric lighting consumed less gas
than direct gas lighting, gas lamps are far cheaper in terms of
cost per delivered candle power.  Electric lights are brighter
and more reliable than gas lamps.  Roughly .13 [m.sup.3]/hr of gas is
needed to energize one gas lamp.  Slightly less gas is needed
for electric lighting, depending on the generator output.(64)
Ghate admits that his data are open to question and that the
high cost of electric lighting might make sense if a generator
also was used for other operations.
Biogas has been used successfully to power all types of internal
combustion engines.  This raises the technical possibility
of biogas providing energy for rural agriculture as well as for
industrial machinery and transportation.  There are various
reports of tractors powered by methane stored in huge bags
towed behind the tractor.  The practicality and economics of
such a scheme are open to question, given little hard data.
Stationary motive power for operating pumpsets, milling and
grinding operations, refrigerators, threshers, chaffers, and
generators, etc., seems to be a more appropriate match between
energy source and end-use demand.  Petrol engines have been run
solely on biogas by the KVIC, several of the Indian Institutes
of Technology, and PRAD, among others.  Since most agricultural
engines are diesel powered, the remainder of this discussion
will be confined to biogas-diesel (dual fuel) engine operation.
The use of biogas in engines could be of great importance to
rural development projects, providing motive power to areas
where the availability or cost of commercial energy (diesel
fuel or electricity) has precluded mechanized activities.
A diesel engine carburetor is easily modified to accommodate
biogas.   The necessary conversion skills and materials exist in
most villages.  Kirloskar Oil and Engines, Limited has marketed
dual fuel biogas-diesel engines for several years at a price
roughly Rs 600 more than regular diesel engines.  Their line
features a modified carburetor and a grooved head for swirling
the biogas, which was found to improve performance.  Kirloskar
does not sell the carburetor separately.  The firm encourages
farmers to consider "the option" when they purchase a new
engine.   Kirloskar engineers report that good engine performance
occurs with a biogas to diesel mixture of 4:1, which works out
to .42 [m.sup.3] of biogas per BHP/hr.(65)  In actual operation, the
ratio may exceed 9:1.  The mixture is regulated by a governor
that reduces the amount of diesel flow as more gas is introduced,
keeping power output constant.  There is an observed drop
in the engine's thermal efficiency with greater gas consumption.
However, research at IIT-Madras has shown that this may
be due to the leanness of the biogas mixture.  Reducing incoming
air improves performance except at full power output.  Generally,
efficiency increases with power output.(66) The gas should be
delivered to the engine at a pressure of 2.57-7.62 cm water
column.(67) Removal of [CO.sub.2] also improves engine performance.
Biogas makes engines run hotter, and therefore proper cooling
is important.  Biogas slurry should not be used to cool engines
since the suspended solids can clog the cooling mechanism and
act as an insulator, thereby trapping heat.  Air-cooled engines
must be used if slurry is mixed with irrigation water that
normally would be used as a coolant.
There is little available data on the potentially corrosive
effects of the [H.sub.2]S present in biogas, although engines have
been run for some time with no reported corrosion.  Iron filings
can be used to filter out [H.sub.2]S.  In addition to the reduced
operating costs for fuel engines, removing [H.sub.2]S has produced the
following benefits:
   1.  Reduced emission of CO.
0    2.  Increased engine life (up to four times normal life).
   3.  At least a 50 percent reduction in maintenance costs due
       to longer life of lubrication oil.   Freedom from gum,
       carbon, and lead deposits.
   4.  Lower idling speed and immediate power response.(68)
When energy conversion efficiency losses are calculated for
diesel generators, roughly 1 kwh is generated for every 0.56 [m.sup.3]
of biogas.  A 15-KVA diesel generator (12 kw) running two 3.75
kw electric pumps (5 hp) for eight hours a day would require
almost 53.8 [m.sup.3]/day, compared to 33.6 [m.sup.3] if the pumps were
powered with dual fuel engines.  This is because of the difficulty
of finding electrical generators that are matched exactly
to peak power requirements.
Slurry Use and Handling
The effluent from a biogas plant can be either sludge, supernatant,
or slurry depending on the design and operation of the
system.   Most Indian systems have slurry as their output.  The
remainder of this discussion pertains to slurry that is formed
primarily by mixing dung and water, although it probably
applies to any digested biomass.
The main advantage of anaerobic digestion is that it conserves
nitrogen if the slurry is handled properly.  Though approximately
20 percent of the total solids contained in the organic
material are lost during the digestion process, the nitrogen
content remains largely unchanged.  The nitrogen is in the form
of ammonia, which makes it more accessible when the effluent is
used as fertilizer.  Aerobic digestion, on the other hand, produces
nitrates and nitrites.  These are likely to leach away in
the soil, do not become as readily fixed to clay and humus, and
are not as easily used by water-borne algae.(69)  Bhatia cites
earlier observations that the amount of ammoniated nitrogen
increases to almost 50 percent of the total nitrogen content of
anaerobically digested dung, as compared to 26 percent in fresh
The quality of organic manures is greatly affected by handling
and storage methods.  Table V-1 shows nitrogen loss related to
storage time.
Biogas slurry can be handled in any of the following ways, with
the choice depending on both cost and convenience:
1.   Semi-dried in pits and carried/transported to the fields.
2.   Mixed with cattle bedding or other organic straw in pits to
    absorb slurry, and then transported to the fields.
3.   If a high water table exists and (1) or (2) are done, then
    the "reformed" slurry that has been mixed with ground water
    can be lifted out of the pit in buckets and dried further.
4.   Applied directly to fields with irrigation water or through
    aerial spraying.(72)
                          Table V-1(71)
           Nitrogen Lost Due to Heat and Volitilization
            in Farmyard Manure (FYM) and Biogas Slurry
                                             Loss as Percentage
Manure                                            of Total N
FYM applied to fields immediately                 0
FYM piled for 2 days before application          20
FYM piled for 14 days before application         45
FYM piled 30 days                                50
Biogas slurry applied immediately                 0
Biogas slurry (dried)                            15
Biogas slurry can be a problem to store and transport, depending
on local land use, the amount of effluent produced daily,
the distance from the digester to the fields, and the willingness
of workers to handle slurry and deliver it to either
household pits or fields.  There may be some merit to evaporating
the water from the slurry, thereby reducing storage space
requirements, and then recycling the water back into the biogas
system.   This should aid the digestion process, facilitate
slurry handling, and reduce net water consumption.
The following are additional benefits of using biogas slurry:
*   Potentially decreasing the incidence of plant pathogens and
   insects in succeeding crops.(73)
*   Speeding the composting process by using additional organic
   materials that can be added to a compost pit.
*   Reducing the presence of odor, white ants, flies, mosquitoes,
   and weed seeds in the compost pits.
*   Making it difficult to steal manure.(74)
It is necessary to compare the nutrient content of biogas slurry
with that of other composting methods to determine the best
use of resources and evaluate alternative investments.   A well-managed
compost pit may yield manure that is only marginally
inferior to that from a biogas system.  The cost of a biogas
system must be compared with the utility of its effluent.  There
is a great deal of confusing literature on the subject, which
analyzes fertilizer contents, handling, and application methods.
More scientific research in this area is needed so that
accurate comparisons between different composting methods can
be made.
The most practical and perhaps most useful kind of research
would be to study field conditions by applying chemical fertilizers,
composted manures, and digested slurry to experimental
plots and carefully monitoring the crop yields for each group.
There have been reports from China indicating that use of biogas
slurry increases crop yields 10-27 percent per hectare compared
areas that receive manure that is aerobically composted.(75)
Unfortunately, and as is the case with much of the
literature on the Chinese experience, there is insufficient
data to substantiate descriptive reports.  In any case, care
should be taken to ensure that handling and application techniques
follow exactly either those methods currently in use in
villages or those that could easily be adopted by villagers.
Too often, the laboratory tells us nothing about actual practice
in the field.
VI.   Economic Analysis of a Village System
Numerous articles and books, have attempted to examine the
economics of biogas systems.(76)  Most of these analyses have been
concerned with family-scale systems, hypothetical village systems,
or the Fateh Singh-Ka-Purva system in Uttar Pradesh.
Often the conclusions of these studies are based on certain
critical assumptions over which, not surprisingly, there is
considerable disagreement.  These assumptions range from values
assigned to capital and annual costs, calorific values for
fuels, and thermal efficiencies, to per capita energy consumption,
market prices, and the opportunity costs of labor,
energy, organic residues, and capital.  The nutrient content and
end-uses of different organic materials also are subject to
It is beyond the scope of this study to untangle these disagreements.
Many of them are due to our limited knowledge of
rural life.  Others are rooted in basic disagreements over
"correct" economic theory, which sometimes approach the level
of a theological dispute or metaphysical debate in which one
either "believes" or "does not believe."   This is especially
true in the cases of social rates of discount and opportunity
costs.   Such questions employ many economists, and it is unlikely
that the following discussions will either threaten those
positions or reconcile such divergent opinions.
Many economic studies attempt to assess the overall impact of
the large-scale adoption of biogas plants.  These include the
costs and benefits to society as a whole, as well as the macro-level
resource demands for steel, cement, manpower, and other
factors required for a massive biogas program.  Such analysis is
valuable when the range of costs and benefits of individual and
village systems is known.  However, this range cannot be determined
accurately at the present time because so little is known
about rural energy consumption patterns.
The analysis presented here has the relatively modest objective
of assessing the performance of a particular biogas system in a
particular village.  It studies a large village-scale system.
Such systems have been more exhaustively analyzed than small
family plants, and also hold more promise for realistically
meeting the energy needs of the rural poor.  Two measures of
performance will be examined.
1.   The net impact of the biogas system on the village economy
    as a whole, determined by the net present value (NPV) of
    quantifiable annual benefits minus costs.  NPV measures the
    value of future benefits and costs and discounts them back
    to the present using a given interest rate.
2.   The ability of the biogas system to bring in enough revenue
    to ensure its self-sufficient operation.  This is measured in
    terms of an undiscounted payback period derived from annual
    income minus annual capital and operating expenditures.
These two performance measurements are useful in determining if
the village "product" is increased as a result of the introduction
of the system and if the system can pay for itself.  Four
limits to these measurements require further discussion.
1.   There are serious shortcomings to such social benefit-cost
    analyses due to the difficulty of quantifying many of the
    effects of a project.(78)   For example, some important values
    pertaining to this study are difficult to measure:
    *  Labor freed from gathering firewood or other fuels, and
       from cooking meals.   The greater amount of useful energy
       from biogas could reduce the time required for cooking by
       one-half to two-thirds.
    *  Decreased incidence of eye and lung diseases and irritations,
       improved cleanliness in the kitchen, and greater
       ease in cleaning cooking utensils due to the clean burning
       biogas.   This is in sharp contrast to chulahs, which spread
       smoke and carbon deposits throughout the kitchen area.
    *  The improved quality and quantity of food consumed due to
       crop yields that are increased because energy is available
       for water pumping, and because the nutrient and humus content
       of the slurry make it a better fertilizer than that
       derived from traditional village composting methods.
    *  Freeing manure piles from white ants, weed seed, and odor,
       and making the manure more difficult to steal due to its
       semi-liquid state.   Theft of manure has been a problem in
       some villages where the manure is scarcer than in the
       village under study here.
    *  Effects of better lighting on education by creating more
       time for readinq and study, on the possible reduction in
       birth rates, and on increased equality among villagers
       because prestigious electric lighting is available to all.
    *  The increased sense of confidence and self-reliance that a
       successful biogas system might instill in the villagers,
       with the long-term potential for greater intra-village
       cooperation, innovation and invention, and employment
       generation and investment.
    *  Changes in the demand for various resources such as fossil
       fuels, chemical fertilizers, etc., and some secondary
       effects associated with these changes such as foreign
       exchange requirements, release of atmostpheric hydrocarbons,
       rate of soil depletion, and deforestation.  Overall
       soil quality might increase if large quantities of
       biogas slurry, which is rich in nitrogen and humus, were
       spread over the fields.
    *  Development of rural industries that require a cheap,
       dependable energy supply, such as biogas.
    *  Impact of the system on the village distribution of income,
       which may vary according to income, cattle, and land
All of these important effects are excluded from the analysis
because of the difficulty of assigning a cardinal value to
them.   This results in lost data and will distort the cost and
benefit calculations.
2.   Net present value (NPV) calculations suffer from a number of
    theoretical limitations, the most serious being the inability
    of an NPV figure to represent fully the real utility of
    a project.   Certainly, a negative or zero NPV indicates that
    a project is not worth pursuing.   However, a positive NPV,
    even if quite large, does not necessarily imply that a project
    should be implemented.   The NPV of a particular project
    must be evaluated along with the NPV of all other projects
    that could be implemented with the same factor inputs of
    natural resources, labor, and capital.  However, these other
    projects may or may not achieve similar goals.  The criteria
    used to select projects may themselves vary according to the
    perceived priority of the goals.   This often depends on who
    is doing the perceiving.   A landless peasant, a block development
    officer, or a social scientist all may have quite
    different ideas about the needs of the poor.  Such are the
    methodological and political complexities of determining the
    best use of resources.   This problem is fundamental to development
3.   Even if one project stands out among many as having the
    greatest NPV, this tells us nothing about the critical problems
    of cash flow and access to capital.   The inclusion of
    cash flow and payback data in the economic analysis that
    follows is presented to help remedy this deficiency.  However,
    even a project that seems financially viable is not
    automatically guaranteed access to capital.  Local and
    national politics, lending institutions' perceptions of the
    project's risks, and/or government perception of a project's
    importance (which affects a variety of possible incentives
    such as price controls, subsidies, loan guarantees, taxes,
    compulsory legislation, etc.) dramatically influence a
    project's financial viability.   The problem of access to
    capital is excluded from the analysis.
4.   All prices used in these calculations are market prices,
    which are affected by the performance of the larger economy
    --inflation, material availability, infrastructure performance,
    government price setting, etc.   Shadow price calculations
    do not alter the fact that benefits and costs will
    occur within the prevailing economic context.  These benefits
    and costs may be subjected to many political and economic
    distortions.   Thus, any analytical framework for assessing
    the project may well distort the "real" impact of the project.
    On the other hand, while reliance on prevailing prices
    and rates of discount may reduce the precision of the following
    analysis, it does account for the actual market
    constraints that a village biogas system would face,
    defining minimal performance requirements.
The village system discussed in the following analysis is being
constructed by the ASTRA group in Pura Village.  It will incorporate
advanced design features and be self-supporting in terms
of its annual operating costs.  (The Karnataka State Government
is providing the capital investment.)  The data base for the
analysis is obtained from A.K.N. Reddy, et al., A Community
Biogas System for Pura Village (1979).
ASTRA has provided information on Pura village and cattle population,
cooking needs, dung availability, and some of the biogas
system component costs.  Unfortunately, much of the actual
data necessary for an accurate analysis are simply not available.
All estimates and assumptions are explained in detail and
are the sole responsibility of the author, who is grateful to
Dr. Reddy for his kind permission to use some of the preliminary
data in this study.  Readers should note that conclusions
that may be drawn from the following discussion should in no
way be used to judge the performance of the actual system under
construction in Pura.  The following analysis proceeds from
certain assumptions that differ slightly from those upon which
the Pura system is based.  Some of the data and cost estimates
for the actual Pura system will be subject to revision.   Nonetheless,
the available data from the Pura system will enable us
to obtain a fair picture of how well a village biogas system
will fare financially.
The ASTRA biogas system under construction in Pura village has
four main functions:
1.   Provide cooking gas for each household.
2.   Operate a pumpset for 20 minutes a day to fill an overhead
    storage tank with water.   This should satisfy village
    domestic water requirements and provide the water needed to
    dilute the dung and clean the inlet and outlet tanks.
3.   Operate a generator for three hours to provide electric
    lighting in the 42 households that currently are not
    connected to the central grid.
4.   Operate a dual fuel engine to run a ball mill as part of a
    rice husk cement manufacturing operation.
The original feasibility study for Pura specified the construction
of a single 42.5 [m.sup.3] ASTRA design digester with a mild
steel floating-drum gasholder.  It would provide enough biogas
for all the above operations.  The release of gas would be
synchronized with various end-uses throughout the day.  The 42.5
[m.sup.3] capacity was determined by the biogas requirements of the
various system tasks, and allowed for some population
The ASTRA team estimated that the 56 households (357 people) in
Pura would require 11,426 [m.sup.3] of gas per year for cooking.   This
averages about 0.088 [m.sup.3] per person per day.  Although this is
less than the 0.2-0.3 [m.sup.3] per person per day norms cited by KVIC
and others, we will assume that ASTRA's figure is correct for
the level of subsistence and diet in Pura village.
The annual gas required to operate all of the engines is estimated
at 3,767 [m.sup.3].  This is calculated as shown in Table VI-1 on
the following page.
Total system requirements for cooking and engine operations are
15,193 [m.sup.3] of gas per year.  Based on ASTRA observations, an
estimated average of 7.35 kg fresh dung per animal can be collected
from the night droppings of tied cattle.  Added to this
figure is an estimated 401.5 kg of collected organic matter--which
also could be 2.65 kg more dung per head.  This gives an
equivalent of 10 kg of dung or dung equivalent per animal per
day.   Regardless of the actual amount of biomas fed into the
system, a 5 percent loss is assumed in collection and handling.
So, of the 532,900 kg available, 506,255 kg/biomass/year is
actually used.  This is roughly 1,387 kg/biomass that could be
fed into the system daily.  These estimates are very conservative.
Cattle population is held constant, and cropping patterns
are unchanged from the present mix.  Both of these factors are
likely to change during the life of the system in a way that
probably will increase the availability of biomass.
The maximum amount of gas produced from these estimates of
Pura's available biomass is described in the analysis as the
maximum output scenario.  The cost of a system designed to produce
only enough biogas to perform specified tasks is described
as the minimum cost scenario.  The two scenarios differ in the
amount of biomass that will be fed into the system.  This
affects the required digester volumes and digester costs.
               Table VI-1.  Annual Gas Requirement
     Function                        Gas Requirement
1.   Water pumping               (20 minutes/day) X (.42 [m.sup.3] gas/
                               BHP/hr) X (5 hp) X (358 days) =
                               251 [m.sup.3]
2.   Operating diesel gener-     (3 hr/day) X (.42 [m.sup.3] gas/BHP/hr)
    ator for lighting           X (5 hp) X (358 days) = 2,256 [m.sup.3]
3.   Operating ball mill for     (2 hr/day) X (.42 [m.sup.3] gas/BHP/hr)
    rice husk cement manu-      X (5 hp) X (300 days) = 1,260 [m.sup.3]
                     TOTAL      3,767 [m.sup.3]
The system is shut down one week each year for repairs,
cleaning, etc., which may become less over time.  It is
assumed that there is no unforseen vandalism, natural
disasters, etc.
The daily biomass charge is determined by the gas requirements
of the tasks to be performed.  It equals the daily gas demand
for all uses divided by the gas yield per kg of biomass.  The
analysis considers three different levels of demand, which
correspond to three different biogas systems.  For each of these
three systems, which are described as Models 1, 2, and 3, both
the minimum cost and maximum output scenarios are examined.   It
should be noted that the digester with sufficient capacity to
digest all the net available biomass--the maximum output
scenario--is identical for all three models.  Because the gas
demand is different in each model due to the different tasks
performed, any surplus gas that will be available in the maximum
output scenario will vary with each model, even though the
digester costs will remain constant.
The three models are described below:
Model 1:   Provides enough biogas for cooking, electric lighting,
          and domestic water requirements for the village,
          as well as water to operate the biogas system.
Model 2:   Provides gas for cooking, electric lighting, water,
          and operating the ball mill to grind rice husks to
          produce rice husk cement.
Model 3:   Provides gas only for electric lighting and the rice
          husk cement operation.
Table VI-2 shows the gas and biomass requirements for the
models, based on earlier calculations.
The Pura village plan calls for two digesters of roughly
21.5 [m.sup.3] capacity each.  Two smaller systems were decided upon
after a risk analysis demonstrated that this reduced the "downtime"
the system due to repairs and maintenance.  At a given
moment, only one of the digesters should be out of service so
that service will not be disrupted completely, as would be the
case with one large digester.  As described in Table VI-1, the
system is assumed to have an annual repair and maintenance
period of one week.
The system used in the following economic analysis is based on
the redesigned ASTRA system with one major modification:   the
analysis assumes that a small volume of water covered by a
sheet of polyethelene is held on top of the gas holders by
retaining walls similar to the ASTRA design described earlier.
The polyethelene is treated for ultraviolet radiation.   This
simple solar water heater reduces system cost and improves performance
due to the increased gas yield that can be expected
from "hot charging" the slurry mixture.  Field reports indicate
that the "hot charge" system, when combined with the practice
of mixing dung with other organic materials, could easily increase
gas yield by 25 percent.
This means the biogas system, which normally would produce gas
at the rate of roughly .038 [m.sup.3]/kg of fresh biomass, now has a
gas yield of .0475 [m.sup.3]/kg of fresh biomass.  This is a very
conservative estimate.  Empirical results may show that gas
yield almost doubles.  While actual gas production rates will
fluctuate slightly due to seasonal ambient temperature changes,
the gas yield of .0475 [m.sup.3]/kg fresh biomass represents an average
or minimum gas production figure, and is used for year
round calculations.
A number of system costs need to be described in detail, since
they differ for each of the models.  The capital costs for two
biogas systems that each have half the total system capacity,
and which are built with ferrocement gas-holders and solar
water heater attachments, are shown in Table VI-3.  Information
is based on detailed calculations and discussions with ASTRA
biogas engineers.  Table VI-4 shows system costs in addition to
digester costs.
ASTRA surveys also indicate that approximately 150,000 kg of
firewood are collected for cooking purposes.  Of that, 4 percent
is purchased at Rs 0.04/kg.  While time spent gathering firewood
is reduced by almost 36,950 hours, the direct annual  monetary
savings that accrue from the biogas system's operation are only
about Rs 240 (150,000 kg of firewood) X (4 percent purchased) X
(Rs .04 kg firewood) = approximately Rs 240.  Despite a relative
             Table VI-2 Gas and Biomass Requirements for Different models
                    Under Minimum Cost and Maximum Output Scenarios
                                  (in [m.sup.3] per day)
                          Model 1                Model 2                Model 3
                                             Cooking, Lighting,    Lighting, Pumping,
                     Cooking, Lighting,       Pumping, and Ball        and Ball Mill
                        and Pumping             Mill Operation           Operation
System Design        Minimum      Maximum      Minimum    Maximum     Minimum    Maximum
  Scenario             Cost       Output       Cost       Output       Cost      Output
Cooking                 31.3        31.3         31.3       31.3         --          --
Water Pumping           0.7         0.7           0.7        0.7       0.7         0.7
Lighting                 6.3         6.3          6.3        6.3        6.3         6.3
Ball Mill               --          --           4.2         4.2        4.2        4.2
Surplus Gas             --         26.7           --        22.5       --         53.8
Total Gas Required
 (Approximately)        38.3       65.0          42.5        65.0      11.2        65.0
Total Annual
Biomass Required    294,306kg   506,255kg   326,579kg  506,255kg   86,021kg   506,255kg
(fresh dung
    Note:  Biomass required for each model is based on a gas yield of .0475 [m.sup.3]/kg.
               Table VI-3 Biogas Digester Capital Costs for Models 1-3
                                  Model 1                Model 2                Model 3
                             Minimum     Maximum    Minimum    Maximum     Minimum    Maximum
                              Cost       Output       Cost      Output       Cost       Output
Daily Gas Capacity ([m.sup.3]  38.3        65.0        42.5       65.0       11.2         65.0
Digester System Cost         13,400      22,100      15,000     22,100      4,500       22,100
             Table VI-4 System Costs for models 1-3 (in Rs)
                                    Model 1         Model 2           Model 3
  5 hp engine and                    15,500          15,500           15,500
    KVA generator
  Electrical system                   5,500            5,500             5,500
  Pumpset                               700              700              700
  Ball mill                             --             4,750            4,750
  Shed for equipment                  3,000           6,000            6,000
  Water tank                            550              550              550
  Miscellaneous (including            8,000            8,000            8,000
    roughly Rs 1,500 for
    technical supervision)
  Subtotal                           33,250          41,000            41,000
  Gas pipeline for village           10,000           10,000             --  
      Total                     43,250     51,000      41,000
abundance of forests, Pura villagers spend an average of three
hours per day collecting firewood.  In other areas, where deforestation
pressures are far more serious, the price of firewood
would be much higher, increasing the value of savings from
reduced firewood consumption.  In such areas, more dung would be
burned as fuel, so greater benefits would be realized by recapturing
the fertilizer value of the dung.  Another possibility
might be that some of the Rs 8,000 used to purchase miscellaneous
material for Model 3 could be freed up, since items like
pipe fittings, valves, etc., would not be needed if the distribution
pipeline were not constructed.  Some of these savings
could be used to purchase improved wood-burning stoves that
could reduce firewood consumption by as much as 50 percent.
This would amount to only Rs 120 in total reduced village firewood
purchases, but would save more than 18,400 hours in collecting
firewood.   Additional benefits and costs that might
accrue from the creation of village woodlots have lot been
No direct government subsidy for the biogas system is considered
in this analysis.  There may be some cases where the NPV
of the system in a village is positive, but the system generates
insufficient cash flow to be viable financially.  Such
cases might justify a possible subsidy if shadow prices and
shadow wage rates are included in the NPV calculations and the
NPV remains positive.
It may be possible for Pura villagers to form an "association"
if they can prove that the project will largely benefit the
poor.   Indian lending institutions can be somewhat flexible
about the criteria used to determine if a particular group can
qualify as an "association."  Associations are eligible to
obtain loans at 4 percent interest.  We have assumed such eligibility
in our calculations, although the effects of a loan at
10 percent also have been analyzed.  To simplify calculations,
it has been assumed in the analysis that loans will be amortized
over 5 years, in equal installments, with a one-year
grace period.  The equal installments are calculated using
coefficients from standard annuity payment tables.  For a 4
percent loan paid back over 5 years in equal installments, the
annual payment equals the total borrowed capital divided by
4.452.   For a loan at 10 percent with similar terms, the annual
payment equals the total borrowed capital divided by 3.791.  The
use of annuity formulas tends to spread capital costs over
time, increasing the NPV of a project.  The distortions caused
by this simplified way of calculating loan payments are very
small in this analysis due to the large operating costs of the
system.   In addition, the impact of inflation on the various
costs and benefits has been ignored.  Rural wage rates are the
largest component of operating costs, and are not expected to
rise significantly.  If they did rise, the increase probably
would be canceled out by the increased savings caused by the
reduced consumption of increasingly costly commercial fuels.)
We have assumed further that dung is provided to the system
free of charge except for labor costs, which are discussed
below.   Slurry also will be distributed freely on the basis of
the amount of dung contributed by each household.  We have
assumed that water and land will be made available for free to
the system by the villagers who have agreed to do so as a
demonstration of their willingness to participate in the
At the time of this writing, there was little information
readily available on the distribution of and crop yields from
land holdings in Pura.  Given a village of Pura's size and population,
the land under cultivation could be approximately 60
hectares.   A typical yield of rice paddy for these holdings
would be 1,500 kg/hectare/year.  An estimate of the average
price a farmer obtains for this paddy is about Rs 90/quintal
(100 kgs).  There is no information on the percentage of
agricultural production consumed by the villagers themselves
versus the percentage that might be sold in markets outside the
village.   To simplify the calculations, we will assume that the
village consumes all that it grows.  Furthermore, we will assume
that the nutrient and humus content of biogas slurry (consisting
of at least all the dung currently applied as manure) is
such that it has the net effect of increasing agricultural
yields by 10 percent over those obtained through current fertilizer
practices, even if these include the application of
chemical fertilizers.
Increases of greater than 10 percent have been reported in
China, where the extensive recycling of agricultural and animal
wastes, including aerobic composting of wastes, is an ancient
tradition.   The 10 percent increase in yield is assumed to be a
net increase over existing methods of "scientific composting."
Thus, if the villagers sold the expected increase in crop
yields, the net increase in village revenue from agriculture
(IA), attributable to the use of biogas slurry equals (60
hectares) X (10 percent increase/hectare) X (1,500 kg of
paddy/hectare) X (Rs 90/100 kg of paddy).  This equals Rs 8,100
for the maximum output scenario.  In the minimum cost scenarios,
proportionately less revenue would be generated because less
biomass would be digested.  The specific IA's for the minimum
cost scenario of each of the three models is calculated by
multiplying Rs 8,100 by the ratio of biomass consumed in each
minimized cost scenario.  That figure then is divided by
506,255, which is the biomass consumed in the maximum output
scenario in all three models.
This measure of  the benefit of biogas slurry is used because it
represents a tangible cash benefit.  Many economic analyses
derive monetary benefits from the use of slurry by assessing
the nutrient content of biogas slurry, determining the equivalent
quantity of chemical fertilizer, and converting this to a
monetary benefit by multiplying the quantity by the unit price
of chemical fertilizer.  The problem with this method is that it
implies that a farmer would have purchased the marginal equivalent
amount of fertilizer.  It is not clear at all that farmers
would have made such purchases in the absence of available
biogas slurry; whether the money is actually "saved" is a
matter of debate.  What is clear is that some increase in agricultural
productivity will occur due to the superior nutrient
and humus characteristics of biogas slurry.  This will result in
increased earnings.  Even so, while the 10 percent increase in
yield is a reasonable estimate, it needs  to be corroborated by
empirical results from field tests that also analyze the yield
empirical alternative composting techniques.
The increased agricultural productivity for the minimum cost
scenario for each Model is calculated by multiplying the ratio
of biomass required for the minimum cost system times the ratio
of biomass required for the maximum output system times Rs
8,100, as explained earlier.  The increased Agricultural productivity
resulting from using the slurry in each of he
minimum cost systems is shown below:
   Model 1  =  294,306 kg   X  Rs 8,100  =   Rs 4,709
               506,255 kg
   Model 2  =  326,579 kg   X  Rs 8,100  =  Rs 5,225
               506,255 kg
   Model 3  =   86,021 kg   X  Rs 8,100  =   Rs 1,376
               506,255 kg
According to ASTRA surveys, Pura village annually consumes
1,938 liters of kerosene, at Rs 2.25 per liter, for lighting.
This annual expenditure of Rs 4,360 for lighting will be
reduced as follows:
   (42 households) X (40 watt bulb/house) X (3 hrs/days) X
(358 days) X (Rs 0.44/kwh) = Consumption (C)
       C      =  approximately Rs 791
However, because the Rs 791 is paid by villagers to the village
biogas operation, it also appears as a village benefit, i.e.,
income from the sale of energy.  Therefore, the village as a
whole saves all money previously spent on kerosene purchases
(Rs 4,360).  In terms of the cash flow position of the biogas
system, the sale of electricity for lighting is treated as
revenue of approximately Rs 791.
A series of costs and benefits related to each model requires
more detailed explanation.  Labor costs for the different models
are as follows:
Model 1:   Cooking, Lighting and Pumping
   1 skilled laborer/supervisor =
      (Rs 7.50/day) X (363 days)             = Rs 2,737.50
   3 unskilled laborers =
      (Rs 5/day) X (3 persons) X (365 days)   = +5,475.00
                     Total labor costs =       Rs 8,212.50
Model 2:   Cooking, Lighting, Pumping and Ball Mill Operation
Model 3:   Lighting, Pumping and Ball Mill Operation
   Same as Model 1                      =     Rs 8,212.50
   Plus the cost of 1 supervisor at
      (Rs 300/month) X (12 months)      =         3,600.00
                               Total     =    Rs 11,812.50
These labor costs are reflected in the cash flow calculations.
However, in the village benefit calculations, it is assumed for
purposes of simplicity and lack of actual data that wages paid
to operate the system will be spent within the village itself.
Therefore, labor "costs" to the village are cancelled by an
equal amount of village "benefits" that would accrue from those
wages being spent on village goods and services.  This clearly
is a gross oversimplification of complex capital flows.  However,
given the orders of magnitude involved, this approach
will suffice for our purposes.
Operation and maintenance costs for each model are shown in
Table VI-5.
         Table VI-5 Annual Operation and Maintenance Costs
                         Model 1       Model 2      Model 3
Digester Maintenance      250.00        250.00       250.00
Diesel Fuel (a)
  for running pumpset       79.75         79.75       79.75
              generator    724.95        724.95       724.95
              ball mill      --            --           --
Lubrication Oil (b)
  for running pumpset       47.25         47.25        47.25
              generator    429.60        429.60       429.60
              ball mill      --          240.00       240.00
Raw Material Purchase (c)   --        4,800.00      4,800.00
(a) A 5 hp dual fuel engine requires .05 liters of diesel fuel/BHP/hour.
At Rs 2.70/liter, a 5 hp engine costs Rs 0.675/hr to
operate.   Diesel fuel consumption figures are derived by:
   Pumping:    (20 minutes/day) X (358 days) X (Rs 675) = 79.75
   Generator:  (3 hours/day) X (358 days) X (Rs 675) = 724.95
   Ball Mill:  (2 hours/day) X (300 days) X (Rs 675) = 405.00
(b) Similarly, lubrication costs for a 5 hp engine/hr are:   (.008
liters of lube oil/BHP/hr) X (Rs 10/liter of oil) X (5 hp) = Rs
.40.   This cost is multiplied by the same running times as shown
(c) 24,000 kg of lime will be purchased from a nearby village at
Rs 0.20/kg, and will be mixed with the ground rice husks to
produce cement.
Finally, we will assume that the surplus gas generated in the
maximum output scenario could be sold at the equivalent diesel
or electricity price, and that demand will keep pace with
supply.   This represents a potentially large source of revenue
to the system.  The conversion factors for the equivalent prices
of diesel and electricity can be calculated as follows:
Surplus gas sold as diesel.  The value of surplus gas sold as
diesel equals the difference between the cost of running an
engine on biogas and the cost of running it on diesel fuel, as
is shown in Table VI-6.
      Table VI-6 Fuel Costs of Generating 1 BHP with a Diesel
                        and a Dual Fuel Engine
                      Standard                  Dual fuel
                    Diesel engine             biogas engine
Diesel fuel      (.25 liters/BHP/hr)       (.05 liters/BHP/hr)
consumed          X Rs 2.70 = Rs .68        X Rs 2.70 = Rs .14
Lubricating       (.015 liters/BHP/hr)      (.008 liters/BHP/hr)
oil consumed     X Rs 10 = Rs .15          X Rs 10 = Rs .08
               Combined cost of diesel   Combined cost of diesel
Total           fuel and lubricating     fuel and lubricating
               oil = Rs .83              oil = Rs .22
The total difference in the combined cost of diesel fuel and
lubricating oil for a standard diesel engine and for a dual
fuel biogas engine is Rs 0.83 - Rs 0.22 = Rs 0.61/BHP/hr.  A
dual fuel biogas engine thus saves Rs 0.61 in fuel and lubricating
oil costs for each hour it operates.
We know that 0.42 [m.sup.3] of biogas are needed to generate one BHP/hr.
We can use the following formula to calculate the Equivalent
Diesel Price/[m.sup.3] (EDP/[m.sup.3]):
(0.42 [m.sup.3] biogas/BHP/hr) X (EDP/[m.sup.3]) = Rs 0.61.
EDP/[m.sup.3]   =  Rs 0.61           =   Rs 1.48/[m.sup.3]
                  Rs 0.42/[m.sup.3]
This shows that biogas is competitive  with diesel fuel when it
can be sold at a price no greater than Rs 1.48/[m.sup.3].  This calculation
uses current prices and assumes that a dual fuel engine
will reduce by half the amount of lubricating oil consumed.
Surplus gas sold as electricity.  The value of surplus gas sold
as electricity is calculated by equating the cost of running a
diesel generator with biogas with the cost of purchasing a kwh
from the central grid.  We know that 1 BHP = .74 kwh, the running
cost of operating a diesel engine to produce 1 BHP-hr = Rs
.22 (from above), and the local cost of electricity is Rs .44/kwh.
Therefore, the equivalent electricity price (EEP) = (.42
[m.sup.3]/BHP/hr) x (EEP/[m.sup.3]) + Rs 0.22 = (.74 kwh/BHP) x (Rs .44) = Rs
The analysis of an energy or development project is only as
good as the quality of its assumptions.  Many studies bury these
assumptions in obscure appendices.  Conclusions and generalizations
made in the body of such studies are rarely subjected to
a critical eye; instead, they are taken by the reader as given.
This study includes the detailed intermediate calculations for
the models to facilitate the reader's understanding and criticism
of the simulations.  Some of the notations--such as the use
of the underline (_) sign--are awkward.  They are written in
this way to correspond in appearance to the computer printouts
in the Appendix, which describe the detailed baseline simulation
for all of the models.  Readers not interested in the mathematical
derivation of the NPV and payback calculations may
skip to pages 61-62 and skim the left-hand column for a sense
of the key benefits and costs.  Conclusions from the analysis
begin on page 75.
Table VI-7 shows the notation, including all constant values,
that is used through the analysis to describe all system variables
for the three models under each scenario.
     Table VI-7 Analysis to Describe All System Variables
D      =   Total biomass yield per annum, corrected for handling
          losses and system down-time as a function of the Minimized
          Cost or Maximized Output scenario.
D_L    =   Diesel required for running a generator set (genset)
          per annum:   (.05 liters/hr/BHP) X (3 hrs) X (5 hp) (358
          days) = 268.5 liters.
D_LC   =   Cost of the digester, gas holder, and solar water
          heater, as a function of system capacity.
D_P    =   Diesel required for pump operation per annum:   (.05
          liters/hr/BHP) X (5 hp) X (20 min/day) X (358 days) =
          29.5 liters.
D_RC   =   Diesel required for running the ball mill used to
          produce rice cement:   (.05 liters/hr/BHP) X (5 hp) X (2
          hrs X (300 days) = 150 liters.
E      =   Cost of all accessories, connections, electrical
          wiring, shelters, pumpsets, genset gas burners, and
          miscellaneous equipment, as a function of tasks to be
          performed in the three Models.
G      =   The gas yield of .0475 [m.sup.3]/kg fresh biomass.
G_C    =   Gas required for cooking per annum.  Calculated earlier
          as approximately 11,425 [m.sup.3].
G_L    =   Gas required for electric lighting per annum = 2,255
          [m.sup.3] biogas (previously calculated).
G_P    =   Gas required for pumping water = 251 [m.sup.3] (previously
G_RC   =   Gas required for operating the ball mill that is used
          in the production of rice husk cement per year:  1,260
          [m.sup.3] biogas (previously calculated).
IA     =   Marginal increase in agricultural income due to nutrient
          and humus content of biogas slurry as a function
          of total quantity of organic material digested, in
          rupees/annum.   Though the actual value of IA will fluctuate
          due to changing crop yields and market prices,
          IA is treated as a constant for the sake of simplicity.
L      =   Labor costs at a function of the different models, in
LO_P   =   Lubricating oil for pumping per annum:  (.008 liters/BHP/hr)
          X (5 hp) X (20 min/day) X (358 days) = 4.7
LO_L   =   Lubricating oil for lighting per annum:  (.008 liters/BHP/hr)
          X (3 hrs) X (5 hp) X (358 days) = 43 liters.
LO_RC =    Lubricating oil for lighting per annum:  (.008 liters/BHP/hr)
          X (2 hrs) X (5 hp) X (300 days) = 24 liters.
LO     =   Total annual cost of lubricating oil:  LO P + LO L + LO
M      =   Material cost (lime) for manufacturing rice husk
          cement, in rupees/year.
N      =   The economic life of the system:  15 years.
N_LC   =   Period in which the loan will be amortized:   five
P      =  Cost of distribution pipeline to supply cooking gas:
         Rs 10,000.
P_D    =  Unit price of diesel fuel at Rs 2.70/liter.
P-DS   =  Unit price of surplus energy sold as diesel at Rs
         148/[m.sup.3] or Rs .74/[m.sup.3].
P-ES   =  Unit price of surplus energy sold as electricity at Rs
         .44/kwh, the current rate in Karnataka, at Rs .2.5/[m.sup.3].
P-FW   =  Unit price of firewood at Rs .04/kg.
P-K    =  Unit prices of kerosene at Rs 2.25/liter.
P-LO      Unit price of lubricating oil at Rs 10.00/liter.
R      =  Revenue from commercial operations--the annual sales
         of rice husk cement.   The Pura village operation hopes
         to produce 80 tonnes of rice husk cement per year.
         This will be sold at Rs 400/tonne, or a total of
         Rs 32,000.   For the purposes of analysis, the effects
         of four levels of annual sales--Rs 0, Rs 10,000, Rs
         20,000, and Rs 30,000--have been calculated.  To
         simplify the analysis, revenue is held constant over
         time.   In  actuality, it would fluctuate with demand.
R-LC   =  Interest rate of loan, calculated at both 4 percent
         and 10 percent.
The following equations have been used for certain intermediate
1.   Annual Recurring Cost Calculations
    Capital Cost of System (K)    =  (D___LC)  +   P + E  + the
                                    Amortization   Coefficient (a
                                    function of N_LC) and (R_LC),
                                    as explained previously).
    Cost of Diesel for Operat-    =  (P__D) X [(D__P) + (D__L) +
    ing the System (DF)              D_RC)].
    Cost of Lubricating Oil       =  (P__L) X [(LO__L) + (LO__P) +
    for Operating System (LO)        (LO_RC)].
    Cost of Operation and         =  L + M + Rs 250 (miscellaneous
    Maintenance                      annual maintenance).
2.   Annual Benefit Calculations
    Energy saved from Reduced     =  (P K) X 1,983 liters of
    Kerosene Consumption             kerosene saved annually
    Energy saved from Reduced     =  (150,000 kg) X (.04 ) X (P_FW),
    Firewood Consumption             as explained previously.
    Total Gas Produced Annu-      = D X G.
    ally (G-T)
    Surplus Gas Available         =  (G T) - [(G C) + (G L) + (G P) +
    Annually (G S)                   (G_RC)].
    Sale of Surplus Gas Con-      =  (G_S) X (P DS) X (0.9).  The
    verted to Diesel                 (0.9) is a utilization factor,
                                    since   not all energy produced
                                    would   be used.
    Sale of Surplus Gas Con-      =  (G_S) X (P__DS) X (0. 9), as
    verted to Electricity            explained above.
3.   Net Benefits--Costs to        =  [Expenditures Saved From Reduced
    village                          Consumption of Kerosene
                                    and Firewood + IA + (Sales of
                                    Surplus Energy at either Diesel
                                    or   Electricity Equivalent
                                    Price) + R] - [Annual Capital
                                    Cost + Diesel Cost + LO + M +
                                    Rs 250].  Labor costs are excluded
                                    from this calculation as
                                    explained earlier.  The Rs 250
                                    is for routine maintenance.
Finally, although all costs are calculated on the basis of the
system operating at full capacity, we will assume that there
will be periodic maintenance delays, and that the system will
not supply gas every day each year.  This will affect the amount
of surplus gas available, and will reduce the benefits realized
from fuel savings of firewood, kerosene, etc.  The daily amount
of biomass still will be fed into the system, so the IA will
remain unaffected.  Since the rice husk cement operation runs
only 300 days a year, the seven-day maintenance is assumed to
occur during the 65-day slack period.  To correct the calculations
for the system's "down time," energy saved from reduced
kerosene and firewood consumption, and sale of surplus gas are
multiplied by one week divided by 52 weeks = 0.981.
Discussion of Modeling Results
We are interested primarily in whether or not the biogas systems
described earlier enable the village to be "better off."
This is measured by the positive NPV, as explained earlier.   We
also are studying whether the systems generate sufficient revenues
to cover their operating and capital costs, as measured
by the undiscounted payback period.  The computer program developed
for this analysis was designed to enable the user to
modify any of the 27 variables to isolate and examine their
effect on economic performance.  For the purposes of this
analysis, two main types of variables were examined.
1.   The interest rate of the loan (R_LC) was examined at 4 percent
    and 10 percent for all models.
2.   The system revenues for the models, the sale of surplus gas
    (P_DS) , and the revenues from the sale of rice husk cement
    (R) were set at various levels.   Revenue from the sale of
    gas, available only in the maximum output scenarios for all
    models, was examined at zero, as well as at the equivalent
    price of:  diesel fuel (Rs 1.48/[m.sup.3]), one-half the equivalent
    price of diesel fuel (Rs .74/[m.sup.3]), and the equivalent price
    of electricity (Rs .25/[m.sup.3]   Revenue from the sale of rice
    husk cement was set in Models 2 and 3 at zero, Rs 10,000,
    20,000, and 30,000. Model 1 has no provisions for running an
In addition, the impact of a hypothetical technological break-through
that somehow reduces the cost of the digesters by 50
percent (1/2 D_LC) was examined.  In this simulation, interest
rates and revenues from the sale of rice husk cement vary, as
explained earlier, and revenues from the sale of surplus gas
are set at zero and the diesel equivalent.
The results from these combinations of different interest
rates, sales of surplus gas, sales of rice husk cement, and
digester costs are shown in the summary Tables VI-10a through
Before discussing the results of this analysis in detail, it
must be remembered that all the figures are rough and indicative
only of orders of magnitude.  For example, in evaluating
the NPV figures, it is most important to note whether or not
the values are positive and "large," such as more than
Rs 10,000.   This enables us to state with reasonable confidence
whether a particular biogas system would provide a village with
a net gain.
Payback figures need to be viewed more exactly.  As the data
will show, differences in the loan repayment schedule, amortized
over five years with a one-year grace period, dramatically
affect the ability of systems to pay for themselves.  Any
system that does not repay the loan in the first year, in addition
to covering its operating costs, will require working
capital from a source that is external to the biogas system.
Even though the system pays for itself in the long run, the
cash flow generated from its operation may be insufficient to
meet short-term debt servicing, especially through the sixth
year of the project.  Thus, if operations are to continue, the
deficit must be offset by an external source of funds.  This
might include user charges or subsidies, as will be discussed
In this analysis, the economic life of system components is
held constant at 15 years for all calculations.  The biggest
source of error here could be a shorter life of the diesel
engine.   But with proper maintenance and the reduced deterioration
observed in laboratory engines run on biogas, an equipment
life of 15 years seems reasonable.  Of the 144 cases examined,
there were seven in which the payback occurred only in the
ninth year or later.  In those seven cases, a 10-year economic
life for system components would mean that the project would
not be financially viable.
The basic challenge to any village embarking on a large-scale
biogas project, of course, is to cover the running capital
costs of the system.  Tables VI-8 and VI-9 below show these
costs in some detail.  The figures in these tables are taken
from the detailed baseline benefit-costs calculations found in
the photocopied computer printouts in the Appendix.
Interest rates will be discussed in greater depth shortly. However,
if the capital for the system were borrowed at the higher
rate of 10 percent, the annual cash flow during the repayment
of the loan would be only 8-10 percent higher than if the money
were obtained at the preferred rate for associations of 4 percent
(as shown in Table VI-8).  In view of the sum of money
involved, the interest is not of great importance.
                            Table VI-8
       Baseline Data:   Annual Operating Deficit (in Rupees)
                for Models 1-3 (Full Cost Digesters)
                              MODEL 1
Years                               Min. Cost           Max. Output
1, 7-15                               8,993                 8,993
2-6 at 4 percent interest           21,718                23,672
    at 10 percent interest           23,936                26,231
                              MODEL 2
Years[\N                                Min. Cost           Max. Output
1, 7-15                              18,038                18,038
2-6 at 4 percent interest           32,863                34,458
     at 10 percent interest          35,448                37,320
                              MODEL 3
Years                               Min. Cost           Max. Output
1, 7-15                              18,038                18.038
2-6 at 4 percent interest           28,258                32,211
    at 10 percent interest           30,040                34,683
Similarly, as shown in Table VI-9, if the costs of the digester
are cut in half due to a technological breakthrough, the annual
cash deficits during repayment of the loan range from only 2-11
percent less than those obtained with the digester at "full"
cost.   Since the other fixed costs of the systems are so large,
savings resulting from reducing the digester costs are surprisingly
trivial when spread over the five-year loan repayment
None of the systems pay for themselves as a result of cash
savings derived directly from operations.  Savings "derived
directly from operations" would include reduced fuel and fertilizer
consumption expenditures and, technically, any multiplier
effect stemming from the alternative use of saved capital.
It would not include revenues from the sale of surplus
gas, surplus slurry, or products or services provided by industries
run on the gas.  This distinction between savings and
revenues is important because the savings will be far less
likely to fluctuate than revenues, which are affected by market
forces.   Savings will accrue as long as demand, prices, and system
performances do not decline.  Of the three models examined,
only model 1 (cooking gas, electric lighting, and village water
pumping) yields a positive NPV from the direct savings accruing
to the village over the system's 15 operating years (see Table
VI-8).   The size of the NPV increases slightly for the systems
with digesters at half cost.  Only in the case of the Model 3
maximum output system (with capital borrowed at 4 percent) does
a negative NPV become positive.  Yet even here, the NPV is an
insignificant Rs 1,497.  Even with no direct revenue from operations,
11-he Model 1 village gains economically from constructing
the system.  Of course, it may be somewhat unfair to
criticize a village system designed to run a small industry
when the projected revenue from the industry is arbitrarily set
at zero.   However, the critical importance of that revenue is
underscored by doing so.
                               Table VI-9
          Baseline Data:   Annual Operating Deficit (in Rupees)
         for Models 1-3, with Digester Costs Reduced 50 Percent
                                     MODEL 1
Years                            Min. Cost           Max. Output
1, 7-15                            8,893                 8,893
2-6 at 4 percent interest        20,213                21,190
    at 10 percent interest        22,169                23,316
                                     MODEL 2
Years                            Min. Cost           Max. Output[N]
1, 7-15                           18,038                18,038
2-6 at 4 percent interest        31,178                31,976
    at 10 percent interest        33,496                34,406
                                     MODEL 3
Years                            Min. Cost           Max. Output
1, 7-15                           18,038                18,038
2-6 at 4 percent interest        27,753                29,729
    at 10 percent interest        29,447                31,768
With all these cautionary notes, we now move to examine the
economic performance of the biogas systems, using different
levels of annual revenue obtained from either the sale of
surplus gas or the sale of rice husk cement (or both).  All data
can be found in  Tables VI-10a through VI-10d below.
Table VI-10a Net Present Value (NPV) and Payback Period at Different Interest Rates for the Three Models
                             With No Revenue from Sales of Rice Husk Cement
         Note:   NPV in rupees is listed first.  Calculations assume a 15-year life of the system.
Payback period in years is in parentheses.  If the system will not pay back over 15 years, (0) is listed.
                                                                         MODEL TWO
                                             MODEL ONE               COOKING, LIGHTING                MODEL THREE
INTEREST RATE         BIOGAS           COOKING & LIGHTING                 & INDUSTRY                 LIGHTING & INDUSTRY
OF THE LOAN           PRICE           Min Cost   Max Output          Min Cost  Max Output            Min Cost   Max Output
(R_LC)                 (Rs/[m.sup.3)     Model     Model               Model      Model                 Model     Model
      4%                  0.00         14,454      33,512             -30,274      -13,902           -44,577       -7,057
                                       (0)         (0)                 (0)          (0)               (0)          (0)
      4%                 0.25                      50,180                             680                          26,438
                                                   (0)                            (0)                            (0)
      4%                  0.74                     82,849                          29,261                          92,087
                                                   (0)                            (0)                            (0)
      4%                  1.48                     132,187                          72,425                         191,231
                                                   (0)                            (0)                            (9)
     10%                  0.00          6,809      24,692             -39,182     -23,768            -50,718       -15,573
                                       (0)         (0)                 (0)          (0)               (0)          (0)
     10%                  0.25                      41,360                          -9,186                          17,921
                                                   (0)                            (0)                            (0)
     10%                  0.74                      74,029                          19,395                          83,571
                                                   (0)                            (0)                            (0)
     10%                  1.48                     123,366                          62,558                         182,715
                                                   (0)                             (0)                            (11)
4% = Interest rate charged to associations.  10% = Higher interest rate.
Rs 0/[m.sup.3] assume no revenues from the sale of biogas; Rs 0.25/[m.sup.3] = Equivalent price of electricity;
Rs 0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] = Equivalent price of diesel fuel.
Table VI-10b Net Present Value (NPV) and Payback Period at Different Interest Rates for the three Models
                                 With Revenues of Rs 10,000 from Sales of Rice Husk Cement
         Note:   NPV in rupees is listed first.  Calculations assume a 15-year life of the system.
Payback period in years is in parentheses.  If the system will not pay back over 15 years, (0) is listed.
                                                                         MODEL TWO
                                             MODEL ONE               COOKING, LIGHTING                MODEL THREE
INTEREST RATE         BIOGAS              COOKING & LIGHTING              & INDUSTRY                 LIGHTING & INDUSTRY
OF THE LOAN           PRICE              Min Cost   Max Output         Min Cost Max Output            Min Cost  Max Output
(R_LC)                 (Rs/[m.suup.3)       Model      Model           Model      Model                Model       Model
     4%                  0.00                                         45,788        62,159            31,485        69,004
                                                                     (0)           (0)               (0)           (0)
     4%                  0.25                                                      76,741                         102,499
                                                                                  (0)                             (0)
     4%                  0.74                                                     105,322                         168,149
                                                                                  (0)                            (15)
     4%                  1.48                                                     148,486                         267,293
                                                                                  (0)                            (1)
    10%                  0.00                                         36,880        52,293            25,344        60,488
                                                                     (0)          (0)               (0)            (0)
    10%                  0.25                                                      66,875                          93,983
                                                                                  (0)                            (0)
    10%                 0.74                                                      95,456                        159,632
                                                                                  (0)                            (0)
    10%                  1.48                                                    138,620                         258,776
                                                                                  (0)                            (1)
4% = Interest rate charged to associations.  10% = Higher interest rate.
Rs 0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0. 25/[m.sup.3] = Equivalent price of electricity;
Rs 0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] = Equivalent price of diesel fuel.
Table VI-10c Net Present Value (NPV) and Payback Period at Different Interest Rates for the Three Models
                       With Revenues of Rs 20,000 from Sales of Rice Husk Cement
        Note:  NPV in rupees is listed first.  Calculations assume a 15-year life of the system.
Payback period in years is in parentheses.  If the system will not pay back over 15 years, (0) is listed.
                                                               MODEL TWO
                                      MODEL ONE            COOKING, LIGHTING            MODEL THREE
OF THE LOAN      PRICE            Min Cost   Max Output     Min Cost   Max Output       Min Cost  Max Output
(R_LC)            (Rs/[m.sup.3])     Model     Model          Model      Model            Model     Model
    4%              0.00                                     121,849      138,220       107,546     145,066
                                                              (0)         (0)          (0)         (0)
    4%              0.25                                                 152,803                   178,560
                                                                         (0)                     (12)
    4%              0.74                                                 181,384                   244,210
                                                                        (11)                      (1)
    4%              1.48                                                224,547                   343,354
                                                                         (7)                      (1)
   10%              0.00                                     112,941      128,354       101,405     136,549
                                                             (0)         (0)           (0)          (0)
   10%              0.25                                                 142,936                   170,044
                                                                         (0)                      (14)
   10%              0.74                                                 171,518                   235,693
                                                                        (13)                      (1)
   10%              1.48                                                 214,681                   334,837
                                                                         (8)                      (1)
4% = Interest rate charged to associations.   10% = Higher interest rate.
Rs 0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0.25/[m.sup.3] = Equivalent price of electricity;
Rs 0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] = Equivalent price of diesel fuel.
Table VI-10d Net Present Value (NPV) and Payback Period at Different Interest Rates for the Three Models
                       With Revenues of Rs 30,000 from Sales of Rice Husk Cement
         Note:   NPV in rupees is listed first.  Calculations assume a 15-year life of the system.
Payback period in years is in parentheses.  If the system will not pay back over 15 years, (0) is listed.
                                                               MODEL TWO
                                      MODEL ONE             COOKING, LIGHTING            MODEL THREE
OF THE LOAN      PRICE            Min Cost   Max Output     Min Cost   Max Output       Min Cost  Max Output
(R_LC)            (Rs/[m.sup.3])     Model     Model          Model      Model            Model     Model
    4%              0.00                                     197,910      214,281       183,607     221,127
                                                              (7)         (7)           (1)         (1)
    4%              0.25                                                 228,864                   254,621
                                                                         (1)                       (1)
    4%              0.74                                                 257,445                   320,271
                                                                         (1)                      (1)
    4%              1.48                                                 300,608                   419,415
                                                                         (1)                      (1)
   10%              0.00                                     189,002     204,415      177,466      212,610
                                                             (8)         (9)           (1)          (7)
   10%              0.25                                                 218,998                   246,105
                                                                         (7)                      (1)
   10%              0.74                                                 247,579                   311,754
                                                                         (1)                       (1)
   10%              1.48                                                 290,742                   410,899
                                                                         (1)                      (1)
4% = Interest rate charged to associations.  10% = Higher interest rate.
Rs 0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0.25/[m.sup.3] = Equivalent price of electricity;
Rs 0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] = Equivalent price of diesel fuel.
Table VI-11a Net Present Value (NPV) and Payback Period at Different Cement Revenue and Interest Rates
                          With the Cost of the Digester Reduced by One-half
           Note:  NPV in rupees is listed first.  Calculations assume a 15-year life of the system.
Payback period in years is in parentheses.  If the system will not pay back over 15 years, (0) is listed.
REVENUE                                                               MODEL TWO
 FROM      INTEREST                         MODEL ONE            COOKING, LIGHTING           MODEL THREE
 SALES     THE LOAN    PRICE            Min Cost   Max Output     Min Cost  Max Output       Min Cost   Max Output
 (Rs)      (R_LC)      (Rs/[m.sup.3])     Model     Model          Model      Model            Model     Model
   0         0.04       0.00            19,641        42,566     -24,468      -5,348       -42,835         1,497
                                        (0)          (0)          (0)          (0)           (0)          (0)
   0         0.04       1.48                        141,740                   80,978                     199,785
                                                     (0)                     (0)                         (8)
   0         0.10       0.00            12,899        34,737     -32,364     -13,723        -48,672        -5,528
                                        (0)           (0)         (0)         (0)            (0)           (0)
   0         0.10       1.48                        133,411                   72,603                     192,760
                                                     (0)                     (0)                         (9)
 10,000      0.04       0.00                                    51,593        70,713        33,226        77,558
                                                                (0)          (0)           (0)            (0)
 10,000      0.04       1.48                                                157,039                    275,846
                                                                             (0)                        (1)
 10,000      0.10       0.00                                    43,697        62,338       27,389         70,533
                                                                (0)          (0)           (0)            (0)
 10,000      0.10       1.48                                                148,665                     268,821
                                                                             (0)                        (1)
4% = Interest rate charged to associations.  10% = Higher interest rate.
Rs 0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0.25/[m.sup.3] = Equivalent price of electricity;
Rs 0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] = Equivalent price of diesel fuel.
Table VI-11b Net Present Value (NPV) and Payback Period at Different Cement Revenue and Interest Rates
                          With the Cost of the Digester Reduced by One-half
           Note:   NPV in rupees is listed first.  Calculations assume a 15-year life of the system.
Payback period in years is in parentheses.  If the system will not pay back over 15 years, (0) is listed.
REVENUE                                                               MODEL TWO
 FROM      INTEREST                         MODEL ONE            COOKING, LIGHTING           MODEL THREE
 SALES     THE LOAN    PRICE            Min Cost   Max Output     Min Cost  Max Output       Min Cost   Max Output
 (Rs)      (R_LC)      (Rs/[m.sup.3])     Model     Model           Model      Model           Model     Model
 20,000      0.04       0.00                                      127,654      146,774       109,288     153,619
                                                                   (0)          (0)          (0)         (0)
 20,000      0.04       1.48                                                  233,100                  351,907
                                                                               (1)                      (1)
 20,000      0.10       0.00                                      119,759      138,339       103,450     146,594
                                                                   (0)         (0)           (0)          (0)
 30,000      0.10       1.48                                                  224,726                   344,882
                                                                               (7)                      (1)
 30,000      0.04       0.00                                      213,715      222,835      185,349     229,680
                                                                   (1)         (1)           (1)          (1)
 30,000      0.04       1.48                                                  309,162                  427,969
                                                                               (1)                      (1)
 30,000      0.10       0.00                                      195,820      214,460       179,511     222,655
                                                                   (7)          (7)           (1)         (1)
 10,000      1.10       1.48                                                  300,787                  420,943
                                                                               (1)                       (1)
4% = Interest rate charged to associations.  10% = Higher interest rate.
Rs 0/[m.sup.3] assumes no revenues from the sale of biogas; Rs 0.25/[m.sup.3] = Equivalent price of electricity;
Rs 0.74/[m.sup.3] = One-half Equivalent price of diesel fuel; Rs 1.48/[m.sup.3] = Equivalent price of diesel fuel.
Model 1--Cooking and Lighting
As discussed earlier, Model 1 has a positive NPV in both the
minimum cost and maximum output cases.  The size of the NPV is
larger in the maximum output case since surplus gas is sold for
profit.   Under the most optimistic conditions--with digester
costs cut in half, the highest price obtained from gas sales
(Rs 1.48, the diesel equivalent), and the 4 percent interest
rate on borrowed capital--the NPV is Rs 140,740.  Even so, as in
all cases of Model 1, the system is unable to generate sufficient
revenue to pay for its annual operating deficits.  These
deficits range from almost Rs 9,000 for years 1 and years 7-15,
to Rs 20,200-26,200 during the loan repayment years, 2-6.  The
system therefore would require either a subsidy or user charge
to finance construction and operation.
Model 2--Cooking, Lighting, and Small Industry
In the minimum cost case, annual cash deficits range from Rs
18,000 for year 1 and years 7-15 to between Rs 31,200-Rs 35,500
in years 2-6 (see Tables VI-8 and VI-9).  Without revenue from
the sale of rice husk cement, the system has a negative NPV and
cannot pay for itself.  When annual sales are greater than Rs
10,000, the NPV becomes positive.  But it is only after sales
reach Rs 30,000 per year that the system pays for itself.   The
higher interest rate only slows payback by one year.  However,
the payback period is 7-8 years, which still necessitates an
external cash source.  The one exception to this is the combination
of the half cost digester with a 4 percent loan, which
pays for itself during the first year.
If the Model 2 system capacity is expanded to accommodate more
biomass input (the maximum output case), then the baseline
annual cash deficits (from Tables VI-8 and VI-9) range from Rs
18,000 in years 1 and years 7-15 to Rs 32,200-Rs 37,300 in
years 2-6.  NPVs are positive if surplus gas is sold at the
price of diesel fuel, at half the price of diesel fuel, and, of
course, if the digester cost is halved and surplus gas is sold
as diesel fuel.  If surplus gas is sold at the equivalent price
of electricity and there are no cement sales revenues, the NPV
is barely positive with a 4 percent loan.  It becomes negative
if the loan is 10 percent, but reverts back to positive if
sales revenues are at least Rs 10,000.  The maximum output case
pays back in 7-8 years (depending on interest rates) if revenues
are at least Rs 20,000 and if the surplus gas is sold at
the diesel equivalent.  It pays back in 11-13 years if the gas
is sold at half the diesel equivalent.  The system does not pay
back if the gas is sold at the electricity equivalent price.
The half-cost digester case pays back in the first year if revenue
is at least Rs 20,000, if gas is sold at the diesel
equivalent, and if the interest rate is 4 percent.  It takes
seven years if the rate is 10 percent.  If revenue is Rs 30,000
and no surplus gas is sold, the situation is much like the
minimum cost case.   There is a payback of 7-9 years, or of 1-7
years if the digester costs are halved.  If revenue is at least
Rs 30,000, and if surplus gas is sold, the payback occurs during
the first year.  However, there is a seven-year payback when
gas is sold at the electricity equivalent and the loan is made
at 10 percent.
Model 3--Lighting and Industry
Based on annual deficits of Rs 18,038 for years 1 and years
7-15, and of Rs 27,700-Rs 30,000 in years 2-6, the minimum cost
systems have positive NPV if revenues from the sale of rice
husk cement are at least Rs 10,000.  They pay back in the first
year if revenues are at least Rs 30,000.  A system designed for
the maximum output case, with either revenue of at least Rs
10,000 or surplus gas sales (at the electricity or diesel
equivalent), shows a positive NPV when the baseline annual
deficit is Rs 18,030 in years 1 and years 7-15, and Rs 29,700-Rs
34,600 in years 2-6.
Payback periods are more complicated.  In the case of a full-price
digester, selling surplus gas at the diesel equivalent
without any revenue from cement sales results in a payback of
9-11 years, depending on the loan rate.  Under similar conditions,
reducing the digester cost by half improves the payback
position only slightly to 8-9 years.  Surplus gas sold at half
the diesel, or electricity, equivalent does not enable the system
to be viable financially.  If no gas is sold, but cement
sales are Rs 10,000, none of the systems pay back.  With sales
of Rs 10,000 and surplus gas sold at the diesel equivalent,
payback occurs during the first year for both the full- and
half-cost digester systems.  With similar cement sales, but with
surplus gas sold at half-diesel equivalent, payback occurs only
in the fifteenth year with a 4 percent loan.  It does not occur
at all at 10 percent or when the gas is sold at the electricity
equivalent.   If no surplus gas is sold, the system does not pay
back if revenue from cement sales are Rs 20,000.  At the diesel
equivalent, and with surplus gas sold in addition to a profit
of Rs 20,000 on cement sales, a system with a full- or halfcost
digester will pay back in the first year.  The same is true
with Rs 20,000 in cement sales, and the surplus gas sold at the
half-diesel equivalent combination.  On the other hand, when the
same level of cement sale is combined with surplus gas sold at
the electricity equivalent, it only yields a 12-14 year payback.
If cement sales are Rs 30,000 and no surplus gas is sold,
the system pays back in either the first or seventh year,
depending on the interest rate.  However, in the half-cost
digester case, the same system pays back immediately, regardless
of the interest rate.  The system has a one year payback
period if cement sales exceed Rs 30,000, and if surplus gas is
sold at any of the three prices.
Certain generalizations can be made from the summary data in
Tables VI-10a through VI-10d:
1.   Of the 144 different ways in which the three models of biogas
    systems might perform, the systems pay back during the
    life of the system in 55 cases (38 percent of the total).  Of
    the cases in which payback occurred, 35 (25 percent) had
    payback within the first year of the project's existence.
    One-fourth of the cases examined seem extremely economical
    when they have an adequate cash flow.   In addition, only 32
    of the 144 cases (22 percent) showed a negative NPV.  This
    suggests that the village will show a net gain from building
    one of these systems in almost 80 percent of the situations
    that were modeled.   However, these optimistic findings presume
    a source of revenue from the sale of rice husk cement
    or surplus gas.
2.   Half of the 144 cases were examined with a 4 percent interest
    rate for borrowed capital; the other half had a 10
    percent rate.   Thirty-two of the 72 cases analyzed at 4
    percent interest paid back during the life of the project.
    Thirty-one cases paid back at 10 percent.  The one remaining
    situation at 4 percent paid back only in the fifteenth year
    of the project.  The remaining eight cases do not pay back at
    all.  Interest rates for borrowed capital do not seem to
    affect the total number of projects that pay back.  Twenty
    two cases pay back during the first year at 4 percent while
    15 cases pay back during the first year at 10 percent.   The
    lower interest rate increases by 10 percent the number of
    systems with an immediate payback.   (Thirty percent of the 4
    percent situations pay back within one year versus 20
    percent for the higher interest cases).  In most cases, the
    higher interest rate extended the payback period by only one
    to two years.   Lower interest rates clearly improve the
    chances for a system to pay back immediately.  But, the
    number of viable projects is relatively unaffected by interest
    rates.  Viable projects are considered to be those with
    those with a means of covering the deficits occurring prior
    to payback, and which require no external source of cash
    during the years of loan repayment.
3.   Of the three basic models examined, Model 1 (cooking, gas
    and electric lighting) does not pay back even when the sale
    of surplus gas and digester costs are cut in half.  Model 2
    (cooking, lighting, and small industry--rice husk cement
    production) payback occurs in 26 of the 64 possible cases.
    Of these, 10 cases (16 percent) pay back during the project's
    first year.   In Model 3 (lighting, rice husk cement
    production), payback occurs in 37 of the 64 possible cases
    (58 percent).   Of these, 27 cases (42 percent) pay back in
    the first year.   Again, the data show the substantial impact
    of being able to sell surplus gas and rice husk cement.
    All things being equal, it is more profitable to maintain a
    village system as a public utility and fertilizer plant than
    as a source of cooking gas.   However, such an approach only
    is possible in a village in which:
    a.  An alternative energy source such as wood from carefully
        managed woodlots could be supplied at an affordable price
        to every household in the village.  This is necessary
        since the system would take away people's only cooking
    b.  An alternative source of animal fodder could be found.
        This is necessary because the biogas system reduces the
        amount of village biomass available for fodder.  This
        might be done by using some of the biogas slurry to grow
        algae or other sources of protein and roughage.  However,
        both algae and roughage cultivation, as well as village
        woodlots, will require more project money, organization
        building, and technical support.   These additional costs
        might be financed with the profits from a system with
        quick payback.  Nonetheless, the opportunity costs of such
        resources cannot be ignored.
        Given the greater managerial complexity and increased
        resource demands of Model 3, in most cases it seems far
        more preferable to link a village system that supplies
        cooking gas with either a small industry or the sale of
        surplus gas.   The concept of using a biogas system as an
        industrial energy unit deserves further study in view of
        the competitive unit energy costs derived from even a
        village-scale system.
4.   Of the 36 cases pertaining to the minimum cost models, eight
    (22 percent) pay back within the life of the project and
    five (14 percent) pay back within the 15 year project life.
    Of these, 32 (30 percent) pay back in the first year.
    Resource opportunity costs, as well as the problem of
    estimating effective demand for surplus gas and rice husk
    cement, bear directly on these findings.  If sufficient
    resources and demand exist, there does seem to be a greater
    chance of economic viability with the larger systems that
    can run an industry and provide additional energy.  But it is
    essential that this question be examined in a particular
    village with its unique set of opportunities and
5.   The minimum cost Models (both 2 and 3) that run an industry
    must realize income of at least Rs 30,000 during the period
    of loan repayment if they are to be viable, even if digester
    costs are halved (see Tables VI-8 and VI-9).  Payback occurs
    in eight of 24 cases.   Of these, five pay back in the first
    year.  The case that comes closest to modeling the expected
    performance of the Pura system (full-cost digester, no sale
    of surplus gas) shows a payback of 7-9 years, depending on
    interest rates.   This result is interesting because it does
    not assume that   capital would be provided free of charge, as
    the Karnataka State Government is doing for Pura.  Nonetheless,
    the project would need assistance during the loan
    repayment years to cover the operating deficit that would
    occur during that period.
6.   In the 18 maximum output cases for each of the Models, surplus
    gas was set at different prices to examine the effect
    of those prices on economic performance.  At the equivalent
    price of diesel (Rs 1.48/[m.sup.3]), 12 cases (67 percent) pay back
    during the life of the project.   Eight of these (44 percent)
    pay back during the first year.   Setting the price at one-half
    the diesel equivalent (Rs .74), nine cases (50 percent)
    pay back.  Six of these (30 percent) pay back in the first
    As one would expect, the lower price of the electricity
    equivalent (Rs .25/[m.sup.3]) yields only six cases that paid back
    (30 percent), and of these, only three paid back in the
    first year (17 percent).   In each of the models, the price of
    surplus gas interacts with the different sales levels of
    rice husk cement.   In 75 percent of these cases, payback
    occurs only if cement sales exceed Rs 20,000.  Systems that
    sell gas at half the equivalent price of diesel fuel perform
    surprisingly well when compared to those that sell gas at
    the full diesel equivalent.   Making energy available at half
    price might well attract certain small-scale industries to
    rural areas.   However, quantities of surplus gas are limited
    since a village must use most of the available biogas to
    meet basic cooking, pumping, and lighting needs.
7.   The effect of cutting digester costs in half was studied,
    assuming that surplus gas sold at the diesel equivalent in
    the maximum output system.   Of the 54 cases examined, digesters
    at full cost paid back in 20 instances (40 percent of
    the total).   Half-cost digesters also paid back in the same
    20 situations.   Full-cost digesters paid back during the
    first year in 11 of these cases (20 percent).  Half-cost
    digesters paid back during the first year in 15 (28 percent)
    of these cases, a slight improvement over the more expensive
    design.  This suggests that, based on the limited number of
    systems examined here, there may be only limited justification
    in devoting a great deal of effort towards reducing
    digester costs.   The effect of cutting digester costs in a
    large-scale system is marginal unless the "fixed costs" of
    labor, diesel engines, generators, and the gas pipeline are
    also reduced.   Even if one could assume that 56 individual
    family-scale plants could be built at Rs 500 each, and if
    labor were free, the costs of installing these plants to
    provide cooking gas and gas lighting easily would approach
    Rs 31,000.   This is not much less than the Rs 43,000 proposed
    for Model 1.  It also ignores the problems of providing an
    adequate supply of water for mixing with the biomass and
    resolving struggles over "dung rights" that might occur with
    family-size plants.
This analysis by no means exhausts all the possibilities of
various system components.  In particular, there are two possible
sources of revenue that have not been included:  user
charges, and returning to the project a portion of income
raised from increased agricultural yields.  Due to the historical
reluctance of many villagers to pay for cooking gas that
substitutes for energy that was perceived as "free," it seemed
sensible to first examine the conditions under which biogas
systems might pay for themselves.  Similarly, given the uncertainties
surrounding the magnitude of increased agricultural
productivity that would be attributed to a biogas system, the
effects of returning to the project a portion of any marginal
increase in agricultural income were excluded from our calculations.
Still, one can speculate about the impact of including
these potential sources of revenue.
From Table VI-8, we know that the annual operating deficit for
the maximum output Model 1 system is Rs 8,993 in years 1 and 7-15,
and Rs 23,672-Rs 26,231 in years 2-6, depending on the
interest rate charged on borrowed capital.  If Rs 4,000 of the
Rs 8,100 expected increase in agricultural income were somehow
returned to the project, the annual operating deficit would be
cut to Rs 4,993 in years 1 and years 7-15 and to Rs 19,672-Rs
22,231 in years 2-6.  If these deficits somehow were divided
among the 56 families, the average cost per family would be
approximately Rs 7.50 per month (Rs 90 per year) for years 1
and 7-15, which seems quite affordable.  The average costs during
the period of loan repayment still would be prohibitive (Rs
397 per year per family).  This figure might be a justification
for a government grant for the cost of system construction.
Since we know that operating costs can be covered by the village,
and the system can sell surplus gas at the diesel equivalent,
the annual revenue would increase by (26.7 [m.sup.3]/day) X (358
days/yr) X (0.9 utilization factor) X (Rs 1.48/[m.sup.3] Diesel
Equivalent Price), which equals Rs 12,730.  If a little over Rs
5,000 of the increased agricultural revenue were returned to
the project, the average user charge per family would be about
Rs 100 per year during the period of loan repayment (years
2-6).   At all other times, the system would show a profit.  We
have not discussed the willingness of villagers, especially
larger land holders, to return a portion of their increased
income to the project.
If nothing else, it should be obvious that the question of
whether or not village-scale biogas systems are economic is one
of considerable complexity.  Under certain assumptions, the biogas
systems analyzed here seem to perform well.  These assumptions
are related to two types of demand:
1.   Rural Energy Demand.   Would villagers be willing to pay user
    charges for gas used for cooking and lighting?  Would small-scale
    industries purchase surplus gas if it were sold at
    prices competitive with diesel fuel and electricity?
2.   Small-Scale Industries Demand.   Which goods and services
    could be produced by small-scale industries that are powered
    by biogas?   Could these goods and services be sold in sufficient
    quantitites to provide biogas systems with needed revenue?
We know very little about these questions, although the methodology
exists for deriving some empirical answers.  Increased
knowledge of rural capital flows and distribution is desperately
needed to determine both the priority that villagers
ascribe to rural energy systems and the economic viability
of these systems.  This is only another way of stating the
obvious, which is that rural energy problems cannot be separated
from the problem of development within a larger political
                  VII.   Village Utilization
As shown in the previous section, the economics of a village-scale
biogas system can be deceptively complex.  Yet of all the
various aspects of biogas systems, the least studied is perhaps
the most important:  how do such systems affect people's lives?
The experience with biogas systems to date sheds little useful
information on this question.  The Chinese claim that they will
have installed as many as 20 million biogas plants by the end
of the early 1980's--depending on which of the various estimates
one reads.  Technical teams sponsored by the UN; the
Intermediate Technology Development Group (ITDG), London; the
International Development Research Center (IDRC), Ottawa; and
others all have reported observing or hearing about "large"
biogas systems.  These usually are connected to an institution
such as a dairy or school.  There is no detailed study available
that documents the existence and performance of an integrated
Chinese biogas production and distribution system that is used
by an entire community.  In fact, the Chinese experience seems
to be distinguished by a reliance on individual family ownership
and maintenance of biogas systems, although the labor,
biomass, and delivery of construction materials may be provided
"free" by a communal production brigade.(79)
Even in China, there is little information available on the
number of biogas plants actually working versus the total
number installed, nor on the performance levels of the working
systems.   S.K. Subramanian, discussing the efforts of other
Asian countries, says that while some nations report the
installation of tens of thousands of systems, the systems are
almost exclusively small-scale family plants.(80)
For many years prior to the watershed 1973 oil embargo, the
KVIC served as an undaunted promoter of biogas systems in
India.   Progress since then has been slow but steady.  At the
close of the fifth Five-Year Plan in 1980, KVIC claimed to have
installed 80,000 family-sized systems in India.  There is no
reliable data on how many of these plants are actually in operation.
An estimate of 50-75 percent was made by several independent
observers contacted during the preparation of this
study.   Despite the fact that the KVIC has trained more than
2,000 people to provide technical assistance throughout India
as part of a youth self-employment project, biogas plant owners
frequently complain about poor servicing and inadequate access
to technical information.  Some of the problems of drum and pipe
corrosion, clogging and scum build-up, and low gas yield are
undoubtedly due to faulty management, improper maintenance, and
insufficient amounts of biomass fed into the digester.  Yet,
because so little effort has been mounted to popularize biogas
systems, and because travel budgets for technical personnel are
so meager, plant operators are rarely informed about solutions
to technical problems.
The government subsidy program designed to stimulate the adoption
of biogas systems is cumbersome and, to a certain extent,
regressive.   Plants with a capacity of more than 6 [m.sup.3] presently
are ineligible for any direct subsidy since they are considered
quite economical.  The result is that wealthier farmers who own
the three or more cattle currently necessary to operate a small
system can receive a subsidy, whereas a village project that
would benefit rich and poor alike is ineligible.  Though the
specific terms of the subsidy have varied over the last several
years, the current program is based on a central government
grant alloted to the state governments.  State governments
actually manage the program by determining the specific guidelines
that will be followed.  In general, 20-25 percent of the
system installation cost is subsidized.  Fifty percent of the
cost generally is borrowed at 9-12 percent interest, payable
over three to five years.  The remainder is paid in cash by the
user, although the relative size of the loan and down payment
vary.   Subsidies usually go directly to the bank to reduce the
size of the loan or to act as collateral.  Few state governments
have authorized designs other than the expensive KVIC model as
eligible for the subsidy.  The government of Uttar Pradesh has
approved the Janata system, but most other state governments
are not aware of the fixed-dome design.  Plants using night soil
also are ineligible.  Delays of one year in obtaining the subsidy
are common.   Many banks do not have a competent staff to
manage the program.  An informal sample of several banks in
Madras revealed that even the chief agricultural loan officers
knew very little about biogas systems and the subsidy program.
The Chinese and, to a lesser extent, the Nepalese biogas programs
are managed by local or regional organizations that were
established specifically to help coordinate funding for and
provide technical assistance to biogas system construction and
operation.   The Chinese seem to have linked regional extension
organizations with macro-level planning bodies so that sufficient
capital and construction materials are generated to fulfill
production targets.  In addition, an extensive promotional
campaign using radio broadcasts, permanent exhibitions, films,
and posters is used to generate interest in biogas plants.
Finally, the Chinese social structure seems to lend itself to
the rapid diffusion of biogas technology.  The traditions of
waste recycling and collective effort are strong.  The system of
government eliminates the need to appeal to individual families
if the communal leadership accepts an idea.  An effective extension
system, in which people are trained to construct and
operate biogas plants and then help train others, generates
technology dissemination by "chain reaction."  At the same time,
a decentralized research and development system appears to have
encouraged a great deal of autonomous local innovation.  Funds
presumably were provided for local experimentation with different
biogas system designs.(81)  Other countries would do well to
study the particulars of the Chinese experience to judge more
accurately which aspects of China's biogas development program
could be adapted to different socio-cultural settings.
The Biogas Corporation, a public/private sector company in
Nepal, guarantees system performance for five years and does
its own installation.  The Agricultural Development Bank of
Nepal provides loans at six percent.
In sharp contrast to both the Chinese and Nepalese programs,
the Indian effort has been fragmented among the KVIC (which
also is charged with promoting more than 20 other small-scale
industries), the Ministries of Agriculture and Rural Reconstruction,
State Khadi Gramodyog (village industry) Boards,
banks, contractors and builders, state agricultural departments,
and agro-industries corporations.  It is remarkable
perhaps that the Indian program has achieved even its modest
success(82) despite the serious problems of inadequate technical
assistance, cumbersome financing procedures, and overlapping or
conflicting institutional jurisdictions.
The KVIC has proposed a program to reach the 12 million families
who own sufficient (three to five) cattle to operate a
family-size biogas system.  The KVIC believes that regional mass
production of prefabricated ferrocement digester/gasholder
segments could significantly lower the costs of small-scale
systems.   Even assuming that individual families pay for
installation and operation of their own systems so that the
government does not have to subsidize biogas systems directly,
and also assuming that the overhead costs (including subsidies,
credit facilities, technical assistance, and staff requirements)
to the government for a large-scale biogas manufacturing
program are only Rs 100 per family, the total overhead costs of
such a program could easily approach Rs 120 crores ($156
Such a program raises a number of important questions regarding
the equitable use of scarce capital and the effects of such a
program on rural income distribution.
Dung is a source of both fuel and income for the poor who, in
addition to using dung they are able to find for cooking and
space heating, also sell dung to generate a meager income.   If
"free" dung becomes monetized, then the poor, who will not have
access to family-scale systems, may be deprived of both income
and fuel.  It may be possible to lessen the cattle-ownership
constraint by a combination of solar heated digesters and the
use of biomass other than dung.  However, the capital costs and
land requirements of these systems would still be beyond the
means of the vast majority of poor village families.
The KVIC scheme also raises the question of tradeoffs between
centralized versus decentralized fabrication of biogas plants.
It is possible that both rapid installation and quality control
would be more easily accomplished if units could be mass-produced.
The possibility does exist for production economies
of scale.  Yet, a more decentralized approach, in which individual
villagers would become skilled in and develop a business
from building and operating biogas systems, might generate far
more employment, consume less steel and cement, and rely more
on local materials that are renewable and have a low opportunity
cost.   Furthermore, it would be likely to foster greater
rural self-reliance and innovation, reducing the potential for
bureaucratic delays, corruption, and infrastructure obstructions
that often plague large-scale, centrally directed projects.
The challenge of a decentralized scheme is how to
develop effective ways of providing technical assistance and
financing for these systems.  Some suggestions for such a
program are contained in the conclusion of this study.
As biogas systems become more dependable and less expensive,
the task of defining the appropriate role of the government in
promoting them assumes greater importance.  It is possible that
a government-sponsored production effort might itself become an
obstacle to the large-scale use of biogas systems.
The most immediate need in the development of biogas systems is
to gain considerably more experience with actual village-scale
systems.   There have been several attempts to develop such systems
in India.  One of these in Kodumenja village, Karimnagar
district, Andhra Pradesh, was sponsored by the Rural Electrification
Corporation, Limited, and the Indian Council of
Scientific and Industrial Research (CSIR).  The system consists
of a ring of 24 interconnected ferrocement floating-drum
digesters, with a total capacity of 128 [m.sup.3].  It is designed to
provide cooking gas and lighting for 60 families, and to operate
five pumpsets.  The system's capital costs are more than Rs
1.25 lakhs ($15,625).  There have been many problems with the
ferrocement domes cracking due to improper fabrication, and the
defective domes have been replaced.  As of May 1980, however,
the system was operating at only half its capacity because the
village was in the midst of a political feud.  Half the population
refused to contribute dung to support a system that would
also benefit their rivals.
Another community-scale plant in the village of Fateh Singh-Ka-Purva,
Bhagayanagar Block, near Ajitmal, Etawah District, Uttar
Pradesh, was designed and installed by PRAD with a grant from
UNICEF.   The system required a capital investment of about Rs
1.65 lakhs ($20,625) for two plants of 35 [m.sup.3] and 45 [m.sup.3] respectively,
a dual fuel 5 hp engine, a generator, gas distribution
pipeline, cooking burners, electrical wiring, and miscellaneous
equipment.   The 80 [m.sup.3] system was to have provided cooking and
lighting (electric) for 27 households (177 people) in addition
to running pumpsets, a chaff cutter, and a thresher.
Fatah Singh-Ka-Purva is an unusual village in that the residents
are relatively comfortable economically.  Almost every
household owns land, and income is distributed rather evenly.
The villagers are of the same occupational caste (shepherds),
and were enthusiastic about building the biogas system.  The
spatial layout of the village is such that all households are
clustered around one or two areas, which simplifies gas distribution

53p86.gif (600x600)

(see Figure VII-1).  Finally, the village initially had
an unusually high cattle to family ratio (4:1), compared to the
national average of 2.5:1.
The advantages Fateh Singh-Ka-Purva enjoyed due to its socio-economic
conditions, the technical competence of PRAD, the
financial and organizational assistance of the local and state
government authorities, and the good offices of UNICEF all were
cast aside somewhat rudely by the unpredictable changes of
nature.   A serious drought resulted in the death or forced sale
of a number of cattle, reducing the cattle population by almost
13 percent (from 117 to 97).  This reduced the amount of dung
available to the system.  The system continues to struggle just
to meet cooking and lighting needs.  It will not be possible in
the immediate future for the biogas system also to run
During the author's visit, a substantial number of dung cakes
were observed drying in the sun.  Ironically, they were spread
around the southern exposure of one of the digester bases.   The
residents of the village are not contributing the required
amount of dung, perhaps 30 percent less than needed.  Some villagers
seem to prefer the taste of milk when it is slowly
boiled over the more diffused heat of dung cakes.  Similarly,
the cooking of rotis, a kind of thin fritter, requires special
burners to distribute heat over a broad surface area.  People
are sometimes inconvenienced by the fixed timings of gas
release, restricted to two hours in the morning and two hours
in the evening, especially if they have to work late in the
fields.   Some fuel is saved to heat water for bathing, washing,
and cooking, especially during the winter months when gas production
falls anyway due to the effect of lower temperature on
microbial digestion.  Finally, the author also observed some
frustration on the part of the site engineer who, having left
the project for two weeks, found certain tasks uncompleted or
improperly executed.  This seems to be related to village
politics; some families do not support the president of the
project "association."
Both these community systems distribute cooking gas freely.
Slurry is distributed proportionately on the basis of per-household
contribution.   People are reluctant to pay for lighting,
which is not perceived as a real need.  Since cooking fuel
formerly was "free," they are unwilling to pay for it now even
though biogas is more convenient and cleaner.  Villagers, while
enthusiastic about the potential of the system, also have the
political accumen to realize that these projects are really not
theirs.   They see that the systems are the showpieces of scientists
and development agencies that cannot afford to let the
projects fail.  When a central government team visited Fateh
Singh-Ka-Purva, villagers inquired what else could be "given"
to them similar to the biogas plant.  No mention was made of
paying for additional services.  The incentive to assume
managerial and operational responsibility for these projects is
simply lacking on the part of the villagers, and eventual self-sufficient
management seems problematic.
Neither system is financially viable, in terms of cash flow,
net present value calculations, or other economic performance
measurements.   In fairness to these projects, it must be remembered
that they were pioneering efforts designed to demonstrate
the technical feasibility of village-scale biogas systems.  They
also are intended to help technologists and planners understand
some of the impact of this technology on village life.  These
goals were accomplished.  While the analyses of economists are
helpful in developing analytical methods and generating useful
data on village household energy consumption patterns,(83) any
criticism of these particular projects on economic grounds,
even if only implied, seems somewhat unfair.  By contrast, the
ASTRA system under construction in Pura village is designed to
be both profitable and self-sustaining.  As such, it represents
the next logical and necessary step in the development of village
biogas systems.
Two of the largest village systems yet attempted in India, each
with a daily capacity of about 200 [m.sup.3], are under construction
in the Gujarati villages of Khoraj, Gandhigram District, and
Khubthal, Ahmedabad District.  These systems are based on the
ASTRA-modified KVIC design, which includes the solar water
heater.   Designed and constructed, and to be managed, by the
Gujarat AgroIndustries Corporation, both systems will supply
more than 100 families in each village with gas for cooking.
Biomass inputs will include dung, human wastes from a community
latrine, and agricultural residues.  According to the unpublished
feasibility report, families will have to pay to connect
their homes to the main gas pipeline.  In addition, all dung
will be purchased, slurry will be sold, and villagers will have
to pay for the gas.  Both systems require an investment of just
over Rs 2 lakhs ($25,000) each.  These systems will receive subsidies
from the state government for approximately one-third of
this investment cost.  It will be interesting to monitor the
progress of these projects, especially the willingness of the
villagers to pay for gas, the performance of the systems and
community latrines, and the long-term financial viability of
the systems.
Technical Questions
Based on what we know about biogas systems, a number of problems
must be resolved before a program can be disseminated on a
large scale.  Relatively little data exists on the net energy
needed to prepare particular meals, nor on how this is affected
by agro-climatic variations, income levels, and local customs.
Such information is necessary to determine the required
capacity of a biogas system in conjunction with whatever other
operations are fueled by the biogas.  More information is needed
on the most efficient stove and burner designs, and on the
effect of different types of cookware materials on gas use.
One of the few benefits of the inefficient and often smoky
chulahs is that the smoke or odor aids in controlling mosquitoes
and termites.  Use of a clean burning fuel such as biogas
might upset this balance.  It may be that biogas systems can be
introduced in certain local situations only in conjunction with
different housing construction techniques or pest control
Slurry handling and distribution can be both time consuming and
annoying.   Villagers express little interest in contributing
free labor to biomass collection and slurry mixing, although in
Fateh Singh-Ka-Purva they do assist in the delivery of slurry
to individual compost piles, central storage pits, or crop
lands.   A large-scale community plant run on a continuous basis
produces more slurry than can be used daily; convenient storage
facilities must be provided.  Alternative means of handling biogas
slurry require further research within the context of village
skills and capital constraints.  These include possible
mechanized distribution, direct application of manure versus
"seeding" existing compost pits, or incorporation into integrated
feed/fertilizer/fuel systems such as algae ponds,
pisciculture, etc.
Water and land use requirements of biogas systems can be substantial.  
Large-scale underground plants can reduce land
requirements unless plants are covered by a solar pond.  Villagers
will have to assess the opportunity cost of land occupied
by a biogas system.  Community biogas technical teams have
in the past viewed the free donation of land and water for biogas
systems as a kind of litmus test of a village's commitment
to the system.  This may not be an unreasonable approach, but it
should not be assumed that land and water will always be available
or close enough to points of use to prevent high distribution
costs.   In addition, ways to recycle the water and reduce
the system's water demand, currently almost equal to the weight
of biomass added, need to be developed.  Finally, the spatial
distribution of huts, sheds, wells, etc., in many villages may
increase gas distribution costs dramatically.  This is due to
both the cost of the pipe and to the need to compensate for
pressure losses over long distances.  These distribution concerns,
coupled with villager complaints about the inconvenience
of fixed timings for the release of gas for both cooking and
lighting,(84) suggest that alternative techniques for the decentralized
storage of gas need to be investigated.  Storage sacks
with a compressible inner bag to maintain sufficient gas
pressure could be developed.  Safety problems--the danger of
explosion due to puncture--and of practical storage volume need
to be surmounted.  The potential advantages of a more decentralized
system have been discussed earlier.
Of course, these technical questions are in addition to numerous
other areas requiring further research and development, as
discussed in Section III.  These include the use of agricultural
and forest residues, the merits of fixed-dome versus floating-drum
and plug-flow designs, the relative importance of constant
gas pressure, and ways to increase gas production throughout
the year.
Financial Viability
The most obvious economic challenge to community biogas systems
is to make them viable financially.  The economic analysis of
the previous section shows that, given the reluctance of villagers
to accept user charges, community biogas systems will
have to find some other way to generate revenue or "cross-subsidization,"
even with significant cost reductions and
improved system performance.  Alternatives could be in the form
of a "subsidiary" commercial operation or the direct sale of
surplus gas to a small-scale industry.  As was mentioned
earlier, speculating on potential revenues is a far cry from
actually generating rural industrial energy demand.  In fact, it
is unclear if the increased availability of inexpensive energy
would be a sufficient stimulus to generate rural industries.
Community biogas systems somehow must demonstrate that external
revenue sources will materialize as expected.  Whether or not
lending institutions develop confidence in such assessments
remains to be seen.
The difficulty in getting villagers to accept user charges will
vary from village to village.  Villages spending a significant
proportion of the "village product" on energy will naturally be
less resistant to some of the progressive pricing schemes suggested
by Parikh and Parikh and by Moulik and Srivastava.(85)
These authors suggest various pricing policies that combine
higher unit prices for wealthier families, and either "free"
(subsidized) community cooking and latrine facilities or the
allocation of gas on the basis of free labor contributions by
the poor.(86)  These sensible pricing policies rely on a series of
untested assumptions regarding the detailed keeping of records
and monitoring of consumption that would be required to make
such systems work.  Furthermore, in many if not most villages,
biogas is a substitute for what villagers perceive to be "free"
fuels:   dung, agricultural residues, or even firewood.  Admittedly,
such a perspective may seem somewhat shortsighted given
deforestation, population growth pressures, and the high cost
in time to a woman who has to walk for hours to gather fuel.
But it is difficult for a villager to justify paying for something
that can be obtained at the low cost of his, or more
likely, her labor.
This outlook raises a much larger question concerning the perception
of both villagers and economists regarding the utility
of investing scarce capital in energy systems.  Are village
energy projects a response to clearly stated village demands,
or are potable water, adequate shelter, an affordable supply of
food, and a sufficient income to release a family from
perpetual debt perceived as more important?  The problem of
"what is to be done" certainly will vary from village to village.
It probably even varies from season to season.  The village
energy bandwagon should be jumped on first by villagers,
and only then by economists and planners.
The overall effect of biogas systems on the local distribution
of income is unknown.  Bhatia and Nairam found that, as one
would expect, energy consumption increases with income.  Even in
a relatively homogeneous village such as Fateh Singh-Ka-Purva,
free cooking gas increases discretionary income the most for
those with the most income.(87)  Some potentially harmful effects
already have been mentioned.  Dung currently is sold by members
of the lower castes to earn a meager income.  A biogas system
might take away that income source from them.  Furthermore, an
increased demand for dung or crop residues might deprive the
poor of fuel.  In addition, people who own more land and cattle
clearly will benefit more from a proportionate distribution of
biogas slurry.  One could even speculate that, over time,
increased agricultural productivity, energy, and income might
make it possible for wealthier villagers to substitute capital
for labor, gradually mechanizing their agricultural operations,
and displacing some farm laborers.
While no one would deny the serious threats posed by deforestation,
it is by no means clear that such ecological damage is
always caused by the increasing rural demand for cooking fuel.
While this undoubtedly may be an important cause in many
specific areas, discussions with staff in the Ministry of
Forestry revealed a great deal of uncertainty about whether it
is the main one.  For example, some large construction firms
allegedly do not report the full number of trees they cut,
harvesting more than they are allowed by permit.
Finally, there has been no attempt to assess the costs of providing
the technical assistance, servicing, financing mechanisms,
and performance monitoring that would have to be an
integral part of any large-scale biogas promotion program.
These overhead costs will occur regardless of whether a large-scale
program creates the decentralized, "spontaneous" adoption
advocated by many village technology groups, or the large,
centrally coordinated, mass-production and installation programs
favored by some in government and industry.  The high
costs of even unprofitable experimental village systems can
only heighten apprehension on this point.  The goal of research
and development efforts must be to generate system designs that
will minimize the dependence of villages on outside money,
material, and technical assistance.
Sociological Questions
The paucity of sociological, anthropological, and organizational
analyses, even of the two community systems discussed
earlier, makes any treatment of such questions a matter of
speculation.(88)   Perhaps the most basic concern is the extent to
which a real sense of community exists in villages where biogas
systems are installed.  It is clear that many villages are in
fact "communities," i.e., they exhibit a shared sense of values
and goals, have cooperative networks that enable the ebb and
flow of daily events to occur reasonably peacefully, and enjoy
a sense of trusted or accountable village leadership.  However,
many villages are less fortunate.  Village life can be quite
tempestuous, with an abundance of rivalries and struggles
related to the rights of caste, marital or family discord, and
indebtedness.   For example, it remains to be seen if people of
one caste will always be willing to consume gas distributed by
the same pipeline that is used by lower castes.
There already is evidence that a serious political feud has
effectively curtailed the operation of the village system in
Kodumunja.   To a lesser extent, factionalism also is operating
in Fateh Singh-Ka-Purva.  This form of protest or manipulation
could seriously affect the cash flow position of a particular
system, especially if loan payments are outstanding or if the
biogas system is linked to one or more external commercial
operations.   If such a disruption, caused either by the withholding
of organic raw material or by outright sabotage, continues
for a long time, the long-term financial viability of
the system and its dependent industries could be threatened.   A
related point is how rugged or durable biogas systems need to
be to survive in the village, and how this affects costs.
An attitude of either cooperation or obstruction may prevail,
depending on the relationship of different interest groups to
the flow of benefits derived from the operation of the biogas
system.   A political minority might want to prevent those in
power from receiving praise from villagers for successfully
operating a biogas system.  Such behavior has been observed in
successful attempts to block the construction of irrigation
canals that clearly would have benefited a village as a whole.
The costs of potential loss of political power resulting from
the construction of the canal were perceived by the victorious
opposition as far greater than whatever gains would have been
realized with the canal's operation.  In addition, the detailed
record keeping necessary for the technical and economical operation
of the system would have conferred a great deal of power
and responsibility on the plant supervisor.  The range of potential
abuse of such power has not been examined in this study
since the dedicated efforts of the technical teams involved in
the current village projects effectively preclude malevolence
and corruption.  However, such individuals may not always be
present in many villages.  The dependence of the villagers on
the ethical conduct of the system manager creates the conditions
for abuse.  Some system of making supervisory personnel
accountable to the villagers clearly is essential.  This might
be done through the Panchayat governments; however, even the
record of these bodies in safeguarding the interests of the
poor is mixed at best.
If villagers, especially women, spend a good portion of their
day collecting fuel and cooking, a biogas system could create a
fair amount of leisure time.  It is not clear how this would be
viewed and utilized by villagers.  Many benefits of a biogas
system will be most attractive to women:  ease and cleanliness
in cooking, freedom from smoky kitchens and associated eye and
respiratory diseases, and freedom from tedious grinding,
threshing, and chaffing operations that could be mechanized
with the use of dual fuel engines.  Will men agree that these
benefits are desirable? It is unclear how much influence women
enjoy over major investment decisions in the family.  This could
be an important consideration in promoting or marketing biogas
The ability of villagers to accept the concepts of collective
ownership and communal living will vary.  Collective ownership
of the land occupied by the biogas system, as well as of the
system itself, cannot be taken for granted.  Similarly, people
may or may not respond positively to community kitchen and
latrine facilities.  Community latrines pose special complications.
First, the flow of water from the latrines to the system
somehow must be regulated so as not to result in excessive
dilution of the biomass fed into the system.  Second, the ritual
of walking to the field early in the morning is one of the few
times during the day when women find the privacy to socialize
among themselves, free from other responsibilities.  This may
also be true for the time spent collecting firewood.  It is not
clear that these practices will be discontinued easily.
Finally, some people view biogas, and "appropriate technology"
in general, as an agent of social change.  They reason that
because these technologies require a great deal of both stewardship
and cooperative action on the part of users, the introduction
of appropriate technologies will foster the necessary
behavior and attitudes, even if these are outside the villagers'
own experience.  Such "technological determinism" may
indeed exist, and there certainly are examples of it.  However,
the critical question remains:  to what extent can a technology
be "beyond" the present village culture and still be adopted by
the villagers without causing undesirable socio-economic
effects?   Given that there is resistance to change, who will
decide that "this" technology is in fact appropriate for
"these" villagers, or that the social change required by a
technology is desirable?  Biogas systems affect some basic
aspects of village life:  the distribution of land, water,
fertilizer, fuel, and income.  It remains to be seen whether
biogas systems can be adopted on a large scale without a political
struggle to secure equitable access to these resources.
These choices, if they are in fact choices, force us to confront
the "appropriateness" of biogas systems.  After much more
experience with these systems, we might be in a position to
evaluate biogas systems as a whole, voicing a collective
approval or disapproval.  But at this stage of development, such
a pronouncement is unwise and potentially destructive.
The problem of actually introducing a technology, such as village-scale
biogas systems, is one of staggering complexity.  No
one has analyzed fully how to transfer such a technology from
the laboratory to the village as a necessary phase of research
and development.  It often is assumed that once technical problems
are solved and biogas systems can pay for themselves on
paper, villagers will accept biogas because it is a good idea
whose time has come.  For example, there is an extremely dedicated,
private group of village energy specialists and biotechnologists
who are working in a number of Tamil Nadu villages.
This group has worked closely with a particular village for
several years and still has a difficult time convincing certain
families to experiment with small family-scale digesters.  The
families agree that biogas is a good thing, but are engaged in
a highly profitable, but illegal, venture, producing arrak (a
strong alcoholic beverage) and selling it in Madras.  These
families feel that their lives are progressing quite nicely and
seem threatened by the presence of outsiders pushing biogas
systems.   Far too little attention has been devoted towards
understanding under what conditions villagers will actually use
biogas systems.  How will they adapt to these systems without
massive, unrealistic, and possibly undesirable intervention by
government officials, engineers,  technologists, or international
lending agencies?
An extensive training program undertaken by a voluntary agency,
Action for Food Production (AFPRO), New Delhi, to train masons
to construct fixed-dome Janata design plants has been only
partially successful.  AFPRO has found that even though masons
know what to do, they lack the self-confidence to construct
these plants without supervision.  AFPRO's experience suggests
that training and extension work for promoting biogas systems
(as well as for technology in general) must deal with psychological
issues as well as with technical knowhow.  If biogas
systems cannot be designed, constructed, operated, and maintained
largely by the people who will use them, their "appropriateness"
in providing energy, fertilizers, and that messy
thing called rural development seems dubious at best.
Nevertheless, it is important to acknowledge that despite the
potentially serious managerial and sociological problems that
may occur during the operations of village biogas systems, this
does not mean such problems necessarily will occur.  There are
numerous examples of villagers adapting to radical departures
from their traditional way of life once they were convinced of
the merits of the new way.  While vested interests will attempt
to control any change, the judicious intervention by a village
elder, popular chief minister, or perhaps even the prime minister,
can immobilize obstructionist forces.  Before such "marketing"
is done, village-scale biogas systems must be economical
and reliable, and their impact on different village groups
better understood.
The point behind this discussion of questions still to be
resolved is not to condemn biogas systems.  Rather, it is to
show that despite a great deal of promise, serious questions do
remain.   By specifying these uncertainties, a much clearer sense
emerges of what is needed in the future.
         VIII.   Conclusions and Recommendations
In 1974, Prasad, Prasad, and Reddy published "Biogas Plants:
Prospects, Problems, and Tasks" in the Economic and Political
Weekly.   This highly influential article is a masterful synthesis
of a great amount of seemingly unrelated data.  It remains
the most concise and comprehensive statement about biogas systems.
In the years since, the ASTRA group, Bangalore, has conducted
extensive research and development to improve system
designs and increase gas yield through the use of solar energy.
ASTRA has also begun to deepen our understanding of village
resource and energy flows.  PRAD, in Lucknow, has undertaken
development and extension of small brick, fixed-dome digester
designs with reasonable success.  Other groups like MCRC,
Madras, have experimented with low-cost hybrid digester designs
and integrated energy-food-fertilizer systems.  Two village-scale
systems have been built and are functioning with mixed
degrees of success, and at least three promising systems are
under construction.  The Department of Science and Technology of
the Government of India has spent Rs 56 lakhs (roughly
$700,000) on its three year, "All-India Coordinated Project on
Biogas."   This program sponsors research on the microbiology of
digestion, ferrocement gas-holder construction, dual fuel
engines, etc., and has established several regional biogas system
testing centers.  Other groups are also conducting experiments
with biogas, as discussed earlier.
After numerous on-site visits and discussions, it seems that
small, nongovernmental, often undercapitalized groups have contributed
most to the further development of biogas systems.  The
government All-India Coordinated Project has not matched the
autonomous small research groups in terms of the quality,
creativity, and long-term usefulness of their research.  The
small teams are often constrained by lack of resources and
insufficient "clout" to secure access to materials and monitoring
equipment.   Furthermore, their often tenuous financial situation
makes it difficult for them to keep dedicated and competent
research, development, and implementation teams intact.
Such groups are especially difficult to maintain due to the
system of rewards and incentives in Indian research.  These
incentives are either heavily biased toward Western basic
research or else respond to the needs of Indian industry and
government agencies.
Despite the achievements of some groups, it is clear that many
of the basic questions posed in the 1974 biogas article in the
Economic and Political Weekly still remain unanswered.  System
performance must improve; costs must be reduced, a variety of
organic matter still awaits practical field level digestion,
the relative advantages of fixed-dome vs. floating-drum gas-holders
must be established, and the unknowns surrounding the
operation and management of village-scale systems remain.  Much
more work needs to be done to piece together the data to answer
these questions more definitively.  In fairness, it must be
noted that system construction, start-up, and operation must be
evaluated for at least one year before any conclusions may be
drawn concerning performance of a particular system.  Even more
time-consuming, and perhaps of greater necessity, is the difficult
process of identifying a village that could use a biogas
system to meet local needs.  Promoters would then need to establish
the trust and credibility to work there, collecting all
relevant data, and finally designing and constructing a large-scale
system.   Biogas systems research also must compete with
the full range of energy technology research, from solar
collectors to breeder reactors.
Happily, the pace of biogas systems work is accelerating.  The
Pura village project will be quite helpful in assessing the
potential contribution of biogas systems in meeting rural
needs.   The Pura system is based on detailed resource surveys
and will be coupled with an industry.  The system is an advanced
design, and has village operation and self-management as a
primary goal.  PRAD is reportedly constructing several large
50-80 [m.sup.3] fixed-dome village-scale systems that should help
answer some of the questions about both the cost and performance
of the fixed-dome design.  There are plans for constructing
6-20 village-scale systems as part of the Department of Science
and Technology's further work in collaboration with KVIC, PRAD,
the Center for Science for Villages, and the Indian Institute
of Management, Ahmedabad.
While more village experience is needed, it is unclear whether
the government sponsored approach will include the most cost-effective
designs, integration of a small industry, and a
genuine attempt to design and implement the systems with the
equal participation of villagers.  Even if the executing group
plans to march into a number of villages and, in the space of
several months, "drop" large-scale biogas systems in those villages
and then monitor system operation, some technical data
will be generated.  However, these systems will be operating in
the peculiar context of an "outside" project that villagers
will treat with the same range of bemused, annoyed, bewildered,
and manipulative attitudes that have been observed in similar
projects.   Such a scheme would be grandiose in scale, but
limited in usefulness.
If the experiences of the dedicated research and extension
groups such as ASTRA, PRAD, Center for Science for Villages,
MCRC, Butwal Technical Institute, Appropriate Technology Development
Association, and others are any guide, the nurturing of
an equal relationship with villagers based on mutual learning
and respect is a difficult, slow process that demands a complex
mix of scientific, management, and communications skills,
coupled with a great deal of commitment on the part of the
technical assistance team.  Effective village energy technology
work and, probably, effective rural development are possible
only if done at the micro-level.
Most of the remaining technical questions concerning biogas
systems could be resolved easily within two to three years
given adequate funding and proper coordination of research
efforts.   Some ways to do this, in order of increasing difficulty,
are suggested below:
1.   Create a network among the small biogas research groups so
that their work becomes complementary and a greater exchange of
experiences and knowledge occurs.  The smaller groups understandably,
and probably correctly, wish to preserve their
autonomy.   They are wary of any incorporation into a large
government-sponsored research effort.  However, these groups
also suffer from an ignorance of each other's work due to poor
communications, financial constraints precluding frequent contacts,
and reluctance for a variety of reasons to take time
away from their own work and share their findings with others.
This network must evolve from the groups themselves so that the
autonomy of each remains unthreatened.  Any external funding for
this type of network, whether from private foundations, government
ministries, or international lending agencies, must protect
the autonomy of the participating groups.  There may be
some tension between the needs of the funding source to have
accountability for its sponsored projects and the desire of
some network participants to merely exchange information and
not publish until their work is completed.  This is not a question
of jealously guarding trade secrets to protect potential
profits or prestige.  Many of these groups have had many painful
experiences with outside interests that distort or exploit
their years of work.  The smaller groups often have special
relationships with villages; outside interference can potentially
undo years of establishing credibility and trust.  Despite
these challenges, the advantages of small groups sharing
their work among themselves are numerous, and a framework for
cooperation can be developed if the groups themselves are
willing to do so.
2.   Create a more harmonious relationship among national planners,
national laboratories, and the smaller research and
development groups.  The exact nature of this relationship is
difficult to specify, and a discussion of Indian institutional
politics and bureaucratic jurisdictions is beyond the scope of
this study.  It would appear possible that smaller research and
development groups could suggest areas of basic research in
which they lack resources or competence.  These areas could then
be taken up by national laboratories and planning bodies.
There are several such research areas worth mentioning:
a.   Analyses of the thermal efficiencies of different fuels as a
    function of the appliances in which the fuels are burned.
    The variations found in different agroclimatic regions must
    be identified so that reliable energy consumption norms can
    be established.
b.   Surveys of energy flows in rural areas to establish a set of
    norms for different agroclimatic areas.  It is essential to
    reduce the number of possible permutations due to customs,
    diet, geography, local costs, appliance efficiency, crop and
    animal husbandry patterns, etc., if rural energy planning is
    to move beyond macro-level guesswork and costly micro-level
c.   Identification of small industries that can make use of the
    type of energy available from biogas systems.  These industries
    must have a high probability of achieving a profit to
    enable a village system to be viable financially.  Their
    various financial, technical, organizational, and marketing
    aspects need to be understood thoroughly.  Some industries
    that seem to have promise are:   dairies; refrigeration; use
    of Ca[CO.sub.2]-based products; grinding; milling; threshing; chaffing;
    food processing, rice husk cement manufacturing; brick
    and tile making; some melting operations; fertilizer manufacturing;
    animal feed and fodder; pyrolytic processes; and
    oil expelling and extraction.
3.   Effective village energy planning will be possible only if
an organizational infrastructure is created to deliver usable
energy technologies to villages.  Such an infrastructure must be
able to undertake:
    a.  An assessment of needs, conducted jointly by villagers
        and planners.
    b.  The development of responses to those needs which may or
        may not involve the installation of such hardware as a
        biogas system.
    c.  The implementation and monitoring of work.
These three phases of rural energy planning must be integrated,
which clearly is a difficult management problem.  This integration
will require some creative organizational development.
Many of the existing groups concerned with rural energy issues
have considerable individual strengths, but are isolated from
each other.  They frequently approach energy planning in a fragmented
way due to limited resources.  The result is that technologists
experiment in laboratories with technologies that are
of questionable use to villagers, while many social scientists
criticize the technologists' R&D efforts, often without understanding
adequately the potential of the technology.  Meanwhile,
voluntary agencies often use unproven technologies whose many
impacts are only dimly appreciated and for which sufficient
financing and technical assistance resources do not exist.
Invariably, these three groups--technologists, social scientists,
and village voluntary agencies--engage in destructive
rounds of recriminations.  A way must be found to bring them
One way to nurture the kind of integration required would be to
form state level rural energy groups.  The state level seems an
appropriate scale in terms of available resources, common language,
politics, and existing institutions and programs.  These
groups would consist of representatives from private research
teams, universities, state government officials, industry,
lending institutions, and voluntary agencies.  While some of
these individual representatives might serve as advisers, there
would also be a need for a full-time staff.  The energy group
would have the following functions:
1.   Coordinate the state-wide rural research and development
efforts of existing institutions, eliminating duplication and
ensuring that research designs incorporate the perspectives of
economists, anthropologists/sociologists, and voluntary
2.   Organize the extensive exchange of rural energy information
within the state, among other Indian states, and with other
countries, especially throughout Asia.  The considerable difficulties
encountered by the author in obtaining reliable information
for this study, necessitating repeated personal visits
throughout India, underscores the need for information
3.   Fund and evaluate demonstration projects, and, if necessary,
create new research groups to do this.
4.   Organize a "rural energy corps."  The corps would consist of
people trained in conducting energy/ecological surveys and
would help villagers select technologies that seem appropriate
to local needs.  It would do this by helping people to obtain
financing, secure access to materials, organize construction or
training programs, and ensure the proper operation and maintenance
of hardware.  The corps would live in strategically chosen
villages for several years to maximize the effect of demonstration
projects, provide ongoing technical assistance, and
monitor progress carefully.  If corps members work with existing
voluntary groups that already have established themselves in
villages, so much the better.  Where no such organizations
exist, the corps could form the nucleus of a larger rural
development effort that would be a natural outgrowth of
"energy" work.
Aided by coordination from the rural energy group and the vast
field experience of the rural energy corps, energy planning
would become an important aspect of development planning.
Energy planning cannot be separated from land use, ownership
patterns, caste relations, the division of labor between men
and women, access to credit, and the economic and political
relationships between urban and rural areas.  It is a dangerous
delusion to treat rural energy planning as a matter of developing
and installing "appropriate" hardware.  A firm link between
the multidisciplinary coordination of the energy group and the
local planning and implementation work of the rural energy
corps, each learning from the other, will help protect against
such myopic planning.
If promising energy technologies, like biogas systems, are to
contribute to rural life, the almost infinite number of system
designs and variations must be reduced and simplified to a few
basic systems.  As Dr. A.K.N. Reddy suggests, this work must be
based on a much deeper understanding of the village economy and
ecosystem.   It may be possible to classify villages broadly by
the nature of their resource flows, and to use biogas system
designs that would correspond to established patterns of consumption.
At a minimum, a methodology must be developed to
allow a technical team to assess easily, quickly, and accurately
a village's resource flows.  Such a methodology is vital for
determining the best investments in energy and other technologies,
and also for the broader development problem of the
optimal use of local resources.  The organization of state-level
energy groups and a rural energy corps would be an important
first step toward addressing some of these questions.
None of this work will be possible without the help and trust
of villagers themselves.  Efforts must be made to reduce the
divisions of caste, religion, and education that have so crippled
India.   One way to begin building a cooperative village
environment is to have a technical team work with a receptive
village leadership to define simple projects that require collective
work.   These projects should be executed easily and have
immediate and demonstrable results, such as improved village
road drainage, construction of pit toilets, or a collective
lift irrigation system.  This would demonstrate the technical
team's credibility and competence, and would provide the villagers
with a sense of confidence and willingness to cooperate.(89)
Using this experience as a foundation, more complex
projects, such as a village biogas system, could be discussed
to see if villagers felt this system made sense to them, given
their perception of their needs.  In this way, villagers could
correctly feel that they chose a biogas system because it would
make their lives easier, and thus would feel a sense of responsibility
and ownership toward the system.  They also would have
confidence in the technical team and themselves, as proved by
the successful completion of the earlier project.
As discussed earlier, a number of areas require more research
and development work to improve the performance of biogas systems.
However, far more effort is needed to link the laboratory
with villagers.  The shifting of emphasis toward joint research
and development in partnership with villagers, responding to
their sense of their needs, would be a radical departure from
the current thrust of much rural energy research, which prefers
the isolation of the laboratory and the cleanliness of the conference
room.   However romantic this approach may sound, it
poses great challenges to scientists, planners, and villagers
alike, even assuming that the will exists to embark upon this
path.   At the moment, it is difficult to be hopeful about the
likelihood of such a commitment.  There are numerous barriers
that make this approach difficult.  Even so, the barriers must
be overcome.  Women and children spend one-third to one-half of
their waking hours collecting fuel.  Crops are lost because
there is no energy to run even installed pumpsets.  Mountainsides
are denuded and croplands destroyed.  Entire generations
of children cannot study in the evening because there is no
light.   While many of these conditions have existed for perhaps
thousands of years, one can only wonder how much longer villagers
will tolerate them, especially given the rising expectations
caused by increasingly modern communications systems and
political and commercial marketing.
During the preparation of this study, the author met literally
hundreds of college students, government officials, university
faculty, and industrialists who were at least convincingly
sincere in their expressed desire to live and work with villages
on rural energy problems.  The often cited obstacle preventing
these educated and committed individuals from doing so
is the absence of an organization that would provide adequate
technical and financial support, both for their work and their
personal lives.  There is a vast, potentially renewable energy
source--human talent--that remains untapped in India.  All that
is needed is the vision to organize it.
    (1) China:   Recycling of Organic Wastes in Agriculture (1978),
FAO Soils Bulletins 40-41; China:  Azolla Propagation and Small-Scale
Biogas Technology (1979).  Also see:   M.N. Islam, "A Report
on Biogas Programme in China" (1979).
    (2) C.R. Prasad, K.K. Prasad, and A.K.N. Reddy, "Biogas Plants: 
Prospects and Problems and Tasks," in Economic and Political
Weekly (1974).  Bombay has had a large-scale municipal sewage
gas plant in operation for some time, as have several other
cities in India.  R.K. Pachauri, Energy and Economic Development
in India (1977) suggests that there is great promise for biogas
systems in urban areas.  There are reports from the People's
Republic of China of municipal plants used to generate electricity.
See Chen Ru-Chen et al., "A Biogas Power Station in
Fashan:   Energy from Night Soil" (1978).
    (3) Roger Revelle, "Energy Use in Rural India," in Science
(June 1976), p. 971.
    (4) Ashok Desai, India's Energy Economy:  Facts and Their Interpretation
(1980), pp. 44-61.
    (5) N.B. Prasad, et al., Report of the Working Group on Energy
Policy (1979), p. 27.
    (6) Revelle, op. cit., p. 970.
    (7) A.K.N. Reddy et al., A Community Biogas Plant System for
Pura Village (1979).  Sheep and goat dung are not included in
the calculations due to the difficulty in collection.   The
8.0 kg/head average fits well with one set of detailed
    (8) Based on empirical observations, ibid.
    (9) KVIC, "Gobar Gas:   Why and How" (1977), p. 14.   Reddy, ibid,
p. 18, observes a higher calorific value biogas (5,340-6,230
kcal/[m.sup.3] but the conservative KVIC figures are used to
account for variations in methane content due to temperature
and cattle diet variation in India.  Also, the calorific value
for crop residues is slightly overstated.  However, in view of
the large amount of biomass, such as water hyacinth, that has
been omitted from the calculations, this calorific value will
    (10) S.S. Mahdi and R.V. Misra, "Energy Substitution in Rural
Domestic Sector--Use of Cattle Dung as a Source of Fuel"
(1979), pp. 3-11.  No data are given for yield of goat dung; 0.1
kg/goat/day has been assumed and the calculation corrected
    (11) Revelle, op. cit., p. 973.
    (12) Reddy, op. cit., p. 21.   This figure, based on data collected
in Pura Village, is a very crude measure of the percentage
of total energy used in cooking.  Little is known about the
all-India range of variations of this figure, especially in the
north where water heating and space heating requirements will
vary seasonally.  The figure probably overstates energy consumed
in cooking.  This is acceptable for our purpose since we are
looking for conservative estimates.
    (13) Ibid, p. 11.
    (14) Fertilizer Association of India, Handbook of Fertilizer
Usage (1980), p. 76.  The calculations of the fertilizer content
of organic materials are therefore conservative estimates.
    (15) Madhi and Misra, op. cit., p. 5.
    (16) The Hindu, 27, July 1980, p. 6, and discussions with the
Fertilizer Association of India.
    (17) N.B. Prasad et al., op. cit., pp. 14-16, 32.
    (18) Ibid., pp. 16, 32.
    (19) See Ashok Desai, op. cit.   National Sample Survey Data and
NCAER fuel consumption surveys are notorious for relying on
interviews rather than actual measurement of fuel consumption.
An all-India survey of energy consumption currently being prepared
by NCAER attempts to improve data collection by establishing
local norms for energy consumed in cooking, heating
water, etc., and then interviewing people about their eating
habits, daily routines, etc. From this data, energy consumption
is computed based on the norms, rather than by asking
people to "remember" or visualize how much firewood they collect
daily.   However, the latter information may be used to
crosscheck survey data.
    (20) One assumption that seems questionable is the rate of substitution
of noncommercial fuels by commercial fuels.  This is
based on rapid progress in coal production and delivery, village
electrification, greater availability of kerosene, increased
hydrogeneration, conservation measures, greater use of
nuclear power, and increased petroleum production to name a
few.   Recent power sector performance would suggest that such
coordination and efficiency is not likely.  Similarly, with population
increasing to an estimated 920 million by the year
2000, it is hard to imagine noncommercial fuel consumption
dropping as the Working Group suggests.  Finally, the effects of
increased agricultural production and the associated increased
availability of crop residues and cattle population (and
therefore dung) are not discussed in any detail.
    (21) Ibid, pp. 35-36.
    (22) Ibid, pp. 70-71.
    (23) Ibid, pp. 37-39.
    (24) These consumption figures are based on discussions with
Kirloskar Oil Engines, Ltd.  Experiments have shown that actual
diesel consumption is reduced 90 percent.  The 80 percent norm
is used to account for performance fluctuations in engines of
different ages, condition, etc.
    (25) Reddy estimates for Pura Village that although a pumpset
cost Rs 5,000, the electricity board can spend upwards of Rs
11,000 connecting the pumpset to the Central Government system.
See Reddy, op. cit., p. 24.
    (26) N.B. Prasad, et al., op. cit., p. 78.
    (27) See National Academy of Sciences (USA), Methane Generation
from Human, Animal, and Agricultural Wastes, (1977), pp. 66-69;
C.R. Das and Sudhir D. Ghatnekar, "Replacement of Cow Dung by
Fermentation of Aquatic and Terrestrial Plants for use as Fuel
Fertilizer and Biogas Plant Feed" (1970); private communication
with R.M. Dave, Jyoti Solar Energy Institute, Vallabh Vidyanagar;
B.R. Guha et al., "Production of Fuel Gas and Compost
Manure from Water Hyacinth and its Techno-Economical Aspects
(sic) (1977); P. Rajasekaran et al., "Effects of Farm Waste on
Microbiological Aspects of Biogas Generation" (1980); T.K.
Ghose et al., "Increased Methane Production in Biogas" (1979);
P.V.R.   Subrahmanyam, "Digestion of Night Soil and Aspects of
Public Health" (1977); N. Sriramulu and B.N. Bhargava, "Biogas
from Water Hyacinth" (1980); FAO, China:  Azolla Propagation
and Small-Scale Biogas Technology (1978); N. Islam, "A Report
on Biogas Programme of China" (sic) (1979), and Barnett et al.,
Biogas Technology in the Third World (1978).
    (28) Personal correspondence with R.M. Dave, op. cit.
    (29) K.V. Gopalakrishnan and B.S. Murthy, "The Potentiality of
Water Hyacinth for Decentralized Power Generation in Developing
Countries," (sic) in Regional Journal of Energy, Heat, and Mass
Transfer, vol. 1, no. 4. (1979), pp. 349-357.
    (30) C.R. Das and S. Gatnekar, op. cit.
    (31) Islam and FAO, op. cit.
    (32) National Academy of Sciences, op. cit.
    (33) Islam, op. cit.
    (34) Sources of information on the microbiological and engineering
aspects of digestion include sources previously cited
(c.f. 30) as well as FAO, China:  Recycling of Organic Wastes in
Agriculture (1978); John L. Fry; Practical Building of Methane
Power Plants for Rural Energy Independence (1974); John Finlay,
"Efficient, Reliable Cattle Dung Gas Plants:  Up-to-date Development
in Nepal" (1978); and the United Nations University,
Bioconversion of Organic Residues for Rural Communities (1979).
    The information contained in the text has been obtained from
the above sources and is a representative compilation of
observed results from both laboratory and field tests.  It
cannot be overemphasized that the figures cited will vary
depending on local conditions.  Any project team referring to
this study or the references cited would be wise to analyze
thoroughly site conditions rather than to use these figures as
the database for a particular project.
    (35) See T.R. Preston, "The Role of Ruminants in the Bioconversion
of Tropical By-Products and Wastes into Food and Fuel," in
United Nations University, op. cit., pp. 47-53.  The author is
grateful to Dr. C.V. Seshadri, Director, Murugappa Chettiar
Research Centre (MCRC) (Madras) for several helpful discussions
on this topic.
    (36) Some of the centers of microbiological research in India
are ASTRA, Indian Institute of Science (Bangalore); Center for
Science for Villages (Wardha); Indian Institute of Sciences
(New Delhi); Maharashtra Association for the Cultivation of
Science (Pune); Shri A.M.M. Murugappa Chetiar Research Centre
(Madras); The National Environmental Engineering Research
Institute (Nagpur); Tamil Nadu Agricultural University
(Coimbatore); and Jyoti Solar Energy Institute, Vallabh
    (37) See Khadi and Village Industries Commission, Gobar Gas:
Why and How, 1979.
    (38) D.K. Subramanian, P. Rajabapaiah and Amulya K.N. Reddy,
"Studies in Biogas Technology, Part II:  Optimisation of Plant
Dimensions," in Proceedings of the Indian Academy of Sciences,
vol. c2, Part 3 (September 1979), op. 365-379.
    (39) Ibid, p. 368.
    (40) Ibid, p. 373.
    (41) P. Rajapapaiah et al., "Studies in Biogas Technology, Part
I:   Performance of a Conventional Biogas Plant," in ibid, pp.
    (42) C.R. Prasad and S.R. Sathyanarayan, "Studies in Biogas
Technology, Part III:  Thermal Analysis," in ibid, pp. 377-86.
    (43) Amulya K.N. Reddy et al., "Studies in Biogas Technology,
Part IV:   A Novel Biogas Plant Incorporating a Solar Water
Heater and Solar Still," in ibid, pp. 387-93.
    (44) S. Bahadur and K.K. Singh, Janata Biogas Plants (1980).
    (45) See E.I. DeSilva, "Biogas Generation:  Development Problems
and Tasks--An Overview," in United Nations University, op.
cit., p. 89.  For additional biogas experiences, see S.K.
Subramanian, Biogas Systems in Asia (1977) and Subramanian's
later abridgement of the same in Barnett et al., Biogas
Technology in the Third World:  A Multidisciplinary Review
(1978), pp. 97-126.
    (46) Personal discussions with MCRC staff, Madras.
    (47) Personal discussions with John Finlay and David Fulford,
Development and Consulting Service, Butwal, Nepal.
    (48) Personal discussions with Dr. S.V. Patwardhan, Director,
Center for Rural Development, Indian Institute of Technology
(Delhi).   MCRC (Madras) is also researching and developing
integrated biomass systems for villages.
    (49) Although the National Academy of Sciences, op. cit., pp.
61-83, contains some helpful illustrations of system planning,
Reddy et al., A Community Biogas Plant System for Pura Village
(1979) is a more comprehensive treatment of the type of
analysis needed to design an appropriate biogas system.  A more
generalized, relatively simple methodology needs to be developed
to enable technical teams and villagers to design energy
systems jointly.
    (50) John Finlay, "Operation and Maintenance of Gobar Plants"
(1978), p. 3.
    (51) National Academy of Sciences, op. cit., p. 85
    (52) Ibid, pp. 92-93.   For an excellent, extremely detailed
troubleshooting methodology, see Finlay, op. cit., pp. 10-16.
    (53) G.L. Patankar, Recent Developments in Gobar Gas Technology
(1977), United Nations Economic and Social Commission for Asia
and the Pacific (ESCAP), Report of the Workshop on Biogas Technology
and Utilization (1975), p. 16.
    (54) Suggested by Amulya K.N. Reddy.
    (55) FAO, China:   Azolla Propagation and Small-Scale Biogas
Technology (1978), p. 59, and Intermediate Technology
Development Group, A Chinese Biogas Manual (1979), p. 64.
    (56) Discussions with villagers using the community system in
Fateh Singh-Ka-Purva.
    (57) Reddy et al., A Community Biogas Plant System for Pura
Village (1979), pp. 36-37.
    (58) Ibid, p. 80.   This figure (.07 [m.sup.3]/person/day) seems low,
but the methodology deriving it is correct.  This suggests that
a re-examination of the database nay be necessary.
    (59) KVIC, ibid, p. 13.   See also:  Ramesh Bhatia, "Economic
Appraisal of Biogas Units in India:  A Framework for Social
Benefit Cost Analysis," in Economic and Political Weekly
(1977), pp. 1515-516, for a related discussion concerning the
need for research in this area.
    (60) Finlay, op. cit., pp. 4-5.
    (61) Intermediate Technology Development Group, op. cit., and
FAO, op. cit., pp. 50-55.
    (62) See photograph, FAO, op. cit., p. 59.
    (63) The author is grateful to John Finlay for this interesting
aspect of prayer rituals in Nepal.
    (64) P.B. Ghate, "Biogas:   A Pilot Project to Investigate a
Decentralized Energy System" (1978), pp. 21-22.
    (65) Kirloskar Oil Engines Limited, "Kirloskar Gobar Gas Dual
Fuel Engine" (1980), p. 6.
    (66) K. Kasturirangan et al., "Use of Gobar Gas in a Diesel
Fuel Engine" (1977).
    (67) ESCAP, op. cit., p. 21.
    (68) Ibid and personal discussions with Kirloskar Engineers.
See also:  Ramesh Bhatia, "Energy Alternatives for Irrigation
Pumping:   Some Results for Small Farms in North Bihar" (1979).
    (69) John L. Fry, Practical Building of Methane Power Plants
for Rural Energy Independence (1974), p. 39.
    (70) Bhatia, op. cit., p. 1507.
    (71) Cited by John Finlay, op. cit., from an earlier study by
Yarwalker and Agrawal, "Manure and Fertilizers" (Nagpur:  
Agricultural-Horticultural Publishing House) (n.d.).
    (72) Finlay, ibid.
    (73) National Academy of Sciences, op. cit., p. 51.
    (74) S.K. Subramanian, "Biogas Systems in Asia:  A Survey" in
Bennett et al., op. cit., p. 99.
    (75) See the brief references to 17 percent increased wheat
yield in Wu Chin County and subsequent discussion concerning
Jiongsu Province, in FAO Soils Bulletin #40, op. cit., p. 47.
    (76) See Andrew Barnett, "Biogas Technology:  A Social and
Economic Assessment," in Barnett et al., Biogas Technology in
the Third World (1978), pp. 69-96; Ramesh Bhatia, "Economic
Appraisal of Biogas Units in India:  A Framework for Social
Cost-Benefit Analysis" (1977).
    "Energy Alternatives for Irrigation Pumping:  Some Results
for Small Farm in North Bihar" (1978); Bhatia and Miriam
Naimar, "Renewable Energy Sources, The Community Biogas Plant"
(1979); P.B. Ghate, "Biogas:  A Pilot Project to Investigate a
Decentralized Energy System" (1978); KVIC, "Gobar Gas:   Why and
How" (1980); Indian Council of Agricultural Research, "The
Economics of Cow Dung Gas Plants" (1976); Arjun Makhiajani and
Alan Poole, Energy and Agriculture in the Third World (1975);
T.K. Moulik, and U.K. Strivatsava, Biogas Plants at the Village
Level:   Problems and Prospect in Gujarat (1976) and Biogas
Systems in India:  A Socio-Economic Evaluation (1978); J.K.
Parikh and K.S. Parikh, "Mobilization and impacts of Biogas
Technologies" (1977); C.R. Prasad, K.K. Prasad, and A.K.N.
Reddy, "Biogas Plants:  Prospects, Problems and Tasks" (1977);
K.K.   Prasad and A.K.N. Reddy, "Technological Alternatives and
the Indian Energy Crisis" (1977); and A.K.N. Reddy et al., A
Community Biogas Plant System for Pura Village (1979).
    (77) See Shishir Mukherjee and Anita Arya, "Comparative
Analysis of Social Cost-Benefit Studies of Biogas Plants"
    (78) See Andrew Barnett, "The Social and Economic Assessment of
Biogas Technology" (1979), David French, "The Economics of
Energy Technologies" (1979), and L. Squire and Herman van der
Tak, Economic Analysis of Projects (1975).
    (79) Islam, op. cit., p. 18.
    (80) Subramaniam, S.K., Biogas Systems in Asia (1977).
    (81) Islam, op. cit., pp. 46-52.
    (82) For an excellent discussion of the performance of KVIC
biogas systems, a socio-economic profile of users, and a solid
analysis of the organizational weaknesses of the Indian biogas
programme, see T.K. Moulik, U.K. Srivastava and P.M. Shingi,
Biogas System in India:  A Socio-Economic Evaluation (1978).  The
author is indebted to Dr. Srivastava for several helpful
discussions on these issues.
    (83) Ramesh Bhatia and Miriam Naimar, op. cit.  This is a
thoughtful analysis of the Fateh Singh-ka-Purva Project.  See
also:   P.B. Ghate, "Biogas:   A Pilot Project to Investigate a
Decentralized Energy System" (1978), and Shahzad Bahadur and
S.C. Agarwal, "Community Biogas Plant at Fateh Singh-Ka-Purva:  
An Evaluation Report" (Lucknow:  PRAD, 1980).
    (84) Bhatia and Naimar, ibid, point out that villages may
actually prefer kerosene for lighting since they control the
timing of its use.  It would be interesting to conduct an
analysis of energy consumption over time, comparing kerosene
lamps and direct biogas lamps.  Despite potentially higher
energy efficiencies with biogas lighting methods, it is possible
that a good deal of gas would be wasted due to the timed
release.   Once the gas is in the pipeline it is subject to
pressure losses, conversion losses (running generators with no
storage battery), and losses due to venting into the atmosphere
if people forget to close a valve or have inefficient lamps.
    (85) These reasons, coupled with an unfamiliarity with the concept
of paying for a "municipal service," cast doubt on the
Parikhs' notion of charging different progressive prices for
the biogas.  See Jyoti K. Parikh and Kirit S. Parikh, "Mobilization
and Impact of Biogas Technologies," in Energy (1977).  The
other problem with this otherwise sensible idea is that it is
not clear that poor people would be willing to cook in community
kitchens even if they would receive gas free or at
nominal cost.  It has proven historically difficult to
"purchase" such cooperative, collective living.
    (86) Ibid, and T.K. Moulik and U.K. Srivastava, Biogas Plants
at the Village Level:  Problems and Prospects in Gujarat (1975),
pp. 110-11.
    (87) Bhatia and Naimar, op. cit., pp. 26-28.
    (88) This section is based on discussions with a great number
of rural social workers, sociologists, private voluntary organizations,
and even a few difficult conversations with some
villagers.   I am especially grateful to Dr. Shivakumar of the
Madras Institute of Development Studies, Dr. Amulya K.N. Reddy,
Indian Institute of Science (Bangalore), Dr. K. Oomen, Department
of Sociology, Jawaharlal Nehru University (New Delhi),
Dr. C.V. Seshadri and Rathindranath Roy, MCRC (Madras), and
Dr. Y. Nayudamma, Central Leather Research Institute (Madras).
See also a very thoughtful article by Hermalata Dandekar,
"Gobar Gas Plants:  How Appropriate are They?"  in Economic and
Political Weekly (1980), pp. 887-92.
    (89) Ibid.  This excellent idea is the way many rural development
teams establish their credibility and create a sense of
the possible through collective effort.  The Sarvodaya Movement
in Sri Lanka is an example of this approach, although it goes
one, perhaps necessary, step further by presenting this narrow
concept of technological change within a highly developed sense
of Buddhist values.  Villagers respond to this because it is a
natural extension of their traditional cultural ethos.
          NPV and Payback Analysis for Baseline Data
                              Models 1-3
          (Full cost digester, no revenue from either
          the sale or surplus gas or rice husk cement)
Note:   For a detailed explanation of symbols used, please refer
       to pp. 59-61 in the text.
VITA is grateful to the Department of Computer Sciences, Indian
Institute of Technology, Madras, India, for providing this
                 MODEL 1:   COOKING & LIGHTING
         D = 294306.00   R =    0.00   P_DS = 0.00   R_LC = 0.04
   D =   2943 6.000    G =         0.047      L =     9212.500     N_LC =     5.000    P_LC =   10.000
   D_L =    273.750    G_C =   11425.000      LO_L =    43.800     P =    10000.000    R =       0.000
   D_LC = 13400.000     G_L =   2300.000      LO_P =      4.800    P_D =       2.700    R_LC =   0.040
   D_P =     30.120    G_P =     253.000      LO_RC =
                                                       0.000     P_DS =     0.000
   D_RC =     0.000    G_RC =      0.000     M =        0.000     P_FW =     0.040
   E =    33250.000    I   =    4709.000     N =         0.000     P_K =      2.250
YEAR                                  1           2           3         4             5            6        7-1C        11-15
  LOAN AMORTIZATION                   0.00   12724.62   12724.62    12724.62    13724.62    12724.62        0.00         0.00
  ENERGY (DIESEL)                   820.45     820.45     820.45      820.45       820.45      820.45    3281.75      4102.24
  LUBE OIL                          486.00     486.00     486.00      486.00       486.00      486.00    1944.00      2430.00
  (LABOR)                          8212.50    8212.50    8212.50     8212.50      8212.50     8212.50   32850.00    41062.50
  OPERATIONS AND MAINTENANCE        250.00      250.00     250.00      250.00       250.00      250.00    1000.00      1250.00
  TOTAL RECURRING COSTS            1556.45    14281.06   14281.06    14281.06    14281.06    14281.06     6225.75      7782.24
  ENERGY SAVED - KEROSENE          4360.50    4360.50    4360.50     4360.50      4360.50     4360.50     17442.00     21802.50
                 FIREWOOD           240.00     240.00     240.00      240.00       240.00      240.00       960.00      1200.00
  INCREASED AGRI PRODUCTIVITY      4709.00   4709.00    4709.00     4709.00      4709.00     4709.00     18836.00     23545.00
  SURPLUS ENERGY INTO DIESEL          0.00       0.00       0.00        0.00         0.00        0.00          0.00        0.00
                       ELECY          0.00       0.00       0.00        0.00         0.00        0.00         0.00         0.00
  REVENUE FROM CCMM OPNS              0.00       0.00       0.00        0.00         0.00        0.00          0.00         0.00
  TOTAL ANNUAL BENEFITS            9222.09    9222.09    9222.09     9222.09      9222.09     9222.09     36388.34     46110.43
+ OPERATIONS & MAINTENANCE)       7665.64   -5058.97   -5058.97  -5058.97      -5058.97      -5058.97     30662.55    38329.18
NET PRESENT WORTH (15 YEARS):    14454.44
+ LABOR + DP. & MAINTENANCE)     -8992.97   -21717.59  -21717.59 -21717.59    -21717.59    -21717.59     -35971.89   -44564.86
                      MODEL 1:   COOKING & LIGHTING
              D = 294306.00   R =     0.00  P_DS = 0.00    R_LC =0.10
   D =   294306.000    G =         0.047      L =     8212.500     N_LC =     5.000    P_LD =   10.000
   D_L =    273.750    G_C =   11425.000      LO_L =    43.800     P =    10000.000    R =       0.040
   D_LC = 13400.000     G_L =   2300.000      LO_P =      4.800    P_D =       2.700    R_LC =   0.100
   D_P =     30.120    G_P =     253.000      LO_RC =
                                                       0.000     P_DS =     0.000
   D_RC =     0.000    G_RC =      0.000     M =        0.000     P_FW =     0.040
   E =    33250.000    I   =    4709.000     N =         0.000     P_K =      2.250
YEAR                                  1           2          3          4             5           6         7-10         11-15
  LOAN AMORTIZATION                   0.00   14943.29   14943.29    14943.29    14943.29    14943.29        0.00         0.00
  ENERGY (DIESEL)                   820.45     820.45      820.45      820.45      820.45       820.45     3281.79     4102.24
  LUBE OIL                          486.00     486.00     486.00      486.00       486.00      486.00    1944.00      2430.00
  (LABOR)                          8212.50    8212.50    8212.50     8212.50      8212.50     8212.50    32850.00    41062.50
  OPERATIONS AND MAINTENANCE        250.00      250.00     250.00      250.00       250.00      250.00    1000.00      1250.00
  TOTAL RECURRING COSTS            1556.45    16499.73   16499.73    16499.73    16499.73    16499.73     6225.79      7782.24
  ENERGY SAVED - KEROSENE          4360.50    4360.50    4360.50     4360.50      4360.50     4360.50     17442.00     21802.50
                 FIREWOOD           240.00    240.00      240.00      240.00      240.00       240.00        960.00     1200.00
  INCREASED AGRI PRODUCTIVITY      4709.00   4709.00    4709.00     4709.00      4709.00     4709.00     18836.00     23545.00
  SURPLUS ENERGY INTO DIESEL          0.00       0.00       0.00        0.00         0.00        0.00          0.00         0.00
                       ELECY          0.00       0.00       0.00        0.00         0.00        0.00         0.00         0.00
  REVENUE FROM CCMM OPNS              0.00       0.00        0.00        0.00        0.00         0.00          0.00        0.00
  TOTAL ANNUAL BENEFITS            9222.09    9222.09    9222.09     9222.09      9222.09     9222.09     36388.34     46110.43
+ OPERATIONS & MAINTENANCE)       7665.64   -7277.64   -7277.64  -7277.64      -7277.64      -7277.64     30662.55    38323.13
NET PRESENT WORTH (15 YEARS):     6808.51
+ LABOR + DP. & MAINTENANCE)     -8992.97   -2353.25   -23936.25 -23936.25    -23536.25    -23936.25     -35971.89   -44564.86
                      MODEL 1:   COOKING & LIGHTING
              D = 506255.00   R =     0.00  P_DS = 0.00    R_LC =0.04
   D =   506255.000    G =         0.047      L =     8212.500     N_LC =     5.000    P_LC =   10.000
   D_L =    273.750    G_C =   11425.000      LO_L =    43.800     P =    10000.000    R =       0.000
   D_LC = 22100.000     G_L =   2300.000      LO_P =      4.800    P_D =       2.700    R_LC =   0.040
   D_P =     30.120    G_P =     253.000     LO_RC =
                                                       0.000     P_DS =     0.000
   D_RC =     0.000    G_RC =      0.000     M =        0.000     P_FW =     0.040
   E =    33250.000    I   =    8100.000     N =         0.000     P_K =      2.250
YEAR                                  1           2           3         4             5            6        7-10        11-15
  LOAN AMORTIZATION                   0.00   14678.80   14678.80    14678.80    14678.80    14678.80        0.00         0.00
  ENERGY (DIESEL)                   820.45     820.45     820.45      820.45       820.45      820.45    3281.75      4102.24
  LUBE OIL                          486.00     486.00     486.00      486.00       486.00      486.00    1944.00      2430.00
  (LABOR)                          8212.50    8212.50    8212.50     8212.50      8212.50     8212.50   32850.00     41062.50
  OPERATIONS AND MAINTENANCE        250.00      250.00     250.00      250.00       250.00      250.00    1000.00      1250.00
  TOTAL RECURRING COSTS            1556.45    16235.24   16235.24    16235.24    16235.24    16235.24     6225.79      7782.24
  ENERGY SAVED - KEROSENE          4360.50    4360.50    4360.50     4360.50      4360.50     4360.50     17442.00    21802.50
                 FIREWOOD           240.00     240.00     240.00      240.00       240.00      240.00       960.00      1200.00
  INCREASED AGRI PRODUCTIVITY      8100.00   8100.00    8100.00     8100.00      8100.00     8100.00     32400.00     40500.00
  SURPLUS ENERGY INTO DIESEL          0.00       0.00       0.00        0.00         0.00        0.00         0.00         0.00
                       ELECY          0.00       0.00       0.00        0.00         0.00        0.00         0.00         0.00
  REVENUE FROM CCMM OPNS              0.00       0.00       0.00        0.00         0.00        0.00         0.00         0.00
  TOTAL ANNUAL BENEFITS           12613.09   12613.09   12613.09    12613.09    12613.09    12613.09      50452.34     63065.43
+ OPERATIONS & MAINTENANCE)      11056.64   -3622.15   -3622.15  -3622.15      -3622.15     -3622.15     44226.55    55283.18
NET PRESENT WORTH (15 YEARS):    33512.33
+ LABOR + DP. & MAINTENANCE)     -8992.97   -23671.77  -23671.77 -23671.77    -23671.77   -23671.77     -35971.89    -44564.86
                              MODEL 1:   COOKING & LIGHTING
                     D =   506255.00  R =    0.00      P_05 = 0.00       R_LC = 0.10
   D =   506255.000     G =        0.047      L =    8212.500      N_LC =      5.000     P_LO = 10.000
   D_L =    273.750     G_C = 11425.000      LO_L =   43.800     P =     10000.000      R =     0.000
   D_LC = 22100.000      G_L =  2300.000      LO_P =    4.800     P_D =       2.700      R_LC =  0.100
   D_P =     30.120     G_P =    253.000     LO_RC =
                                                      0.000     P_DS =      0.000
   C_RC =     0.000     G_RC =     0.000     M =       0.000      P_FW =      0.040
   E =    33250.000     IA =    8100.000      N =       0.000      P_K =       2.250
YEAR                                      1            2            3           4            5            6          7-10         11-15
  LOAN AMORTIZATION                       0.00    17238.20    17238.20     17238.20     17238.20    17238.20         0.00          0.00
  ENERGY (DIESEL)                       320.45      320.45      820.45       820.45       820.45      820.45      3281.75       4102.24
  LUBE OIL                              486.00       486.00      486.00      486.00       486.00       486.00      1944.00      2430.00
  (LABOR)                              8212.50      8212.50     8212.50      8212.50      8212.50     8212.50     32950.00      41062.50
  OPERATIONS AND MAINTENANCE            250.00       250.00      250.00       250.00       250.00      250.00      1000.00       1250.00      
  TOTAL RECURRING COSTS                1536.45     18794.64     18794.64    18794.64    18794.64     18794.64       6225.79      7782.24
  ENERGY SAVED - KEROSENE              4360.50      4360.50     4360.50      4360.50      4360.50     4360.50     17442.00      21802.50
                 FIREWOOD               240.00       240.00      240.00       240.00       240.00      240.00       960.00       1200.00
  INCREASED AGRI PRODUCTIVITY          8100.00      8100.00     8100.00      8100.00      8100.00     8100.00     32400.00      40500.00
  SURPLUS ENERGY INTO DIESEL              0.00         0.00        0.00         0.00         0.00        0.00         0.00          0.00
                      ELEC Y              0.00        0.00         0.00         0.00         0.00        0.00         0.00          0.00
  REVENUE FROM COMM OPNS                  0.00        0.00          0.00        0.00         0.00        0.00         0.00          0.00
  TOTAL ANNUAL BENEFITS               12613.09    12613.09      12613.09    12613.09    12613.09     12613.09      50452.34     63065.43
+ OPERATIONS & MAINTENANCE)          11056.64   -6181.55      -6181.55     -6181.55    -6181.55    -6181.55      44226.55      55283.13
NET PRESENT WORTH (15 YEARS):        24692.20
+ LABOR + DP. & MAINTENANCE)         -8992.97   -26231.16    -26231.16   -26231.16    -26231.16   -26231.16     -35971.39     -44964.86
                                                MODEL 2:  COOKING, LIGHTING & INDUSTRY
                                        D = 326579.00  R =       0.00  P_DS = 0.00   R_LC = 0.04
   D =   326579.   0     G =        0.047     L =    11812.500     N_LC =     5.000    P_LO = 10.000
   D_L =    273.750     G_C = 11425.000     LO_L =    43.800    P =     10000.000     R =     0.000
   D_LC = 15000.000      G_L =  2300.000     LO_P =     4.800    P_D =       2.700    R_LC =  0.040
   D_P =     30.120     G_P =    253.000    LO_RC =
                                                      0.000    P_DS =      0.000
   C_RC =   150.000     G_RC = 1260.000     M =     4800.000    P_FW =      0.040
   E =    41000.000     IA =    5225.000    N =        0.000     P_K =      2.250
YEAR                                    1             2             3            4             5             6          7-10         11-15
  LOAN AMORTIZATION                     0.00     14824.80     14824.80      14824.80      14824.80     14324.80         0.00          0.00
  ENERGY (DIESEL)                    1225.45      1225.45      1225.45       1225.45       1225.45      1225.45      4901.79       6127.24
  LUBE OIL                            726.00        726.00       726.00       726.00        726.00        726.00      2904.00      3630.00
  (LABOR)                           11812.50      11812.50     11812.50      11812.50      11812.50     11812.50     47250.00      55062.50 
  OPERATIONS AND MAINTENANCE         5050.00       5050.00      5050.00       5050.00       5050.00      5050.00     20200.00      25250.00
  TOTAL RECURRING COSTS              7001.44      21826.24     21826.24      21826.24      21826.24     21826.24     28005.77      35007.21
  ENERGY SAVED - KEROSENE            4360.10       4360.50      4360.50       4360.50       4360.50      4360.50     17442.00      21802.50
                 FIREWOOD             240.00        240.00       240.00        240.00        240.00       140.00       960.00       1200.00
  INCREASED AGRI PRODUCTIVITY        5225.00       5225.00      5225.00       5225.00       5225.00      5225.00     20900.00      20125.00
  SURPLUS ENERGY INTO DIESEL            0.00          0.00         0.00          0.00          0.00         0.00         0.04          0.00
                    ELEC Y              0.00          0.00         0.00          0.00          0.00         0.00         0.00          0.00
 REVENUE FROM COMM OPNS                 0.00          0.00          0.00          0.00         0.00         0.00          0.00          0.00
 TOTAL ANNUAL BENEFITS               9738.09       9738.09       9738.09      9738.09      9738.09       9738.09      38952.34     48690.43
+ OPERATIONS & MAINTENANCE)         2736.60     -12088.15      12088.15      -12088.15   -12088.15    -12088.15     -10946.58     13683.22
NET PRESENT WORTH (15 YEARS):      20273.67
+ LABOR + DP. & MAINTENANCE)      -19037.57     -32862.77     -32862.77     -32862.77   -32862.77    -32862.77     -72151.88    -90189.8
                                                MODEL 2:  COOKING, LIGHTING & INDUSTRY
                                        D = 326579.00  R =      0.00    P_DS = 0.00   R_LC = 0.10
   D =   326579.000     G =        0.047      L =    11812.500      N_LC =    3.001     P_LC = 10.000   
   D_L =    273.750     G_C = 11425.000      LC_L =    43.800     P =    10000.000      R =     0.000   
   D_LC = 15000.000      G_L =  2300.000      LC_P =      4.800     P_D =      2.700     R_LC =  0.100
   D_P =     30.120     G_P =    253.000     LC_RC =                          
                                                       0.000      P_DS =    0.000
   C_RC =   150.000     G_RC = 1260.000      M =     4800.000     P_FW =     0.040
   E =    41000.000     IA =    5225.000      N =        0.000      P_K =     1.250
YEAR                                       1          2             3            4             5             6          7-10          11-15
  LOAN AND AMORTIZATION                 0.00      17409.66     17409.66      17409.66      17409.66     17409.66        0.00          0.00
  ENERGY (DIESEL)                    1225.45      1225.45      1225.45       1225.45       1225.45      1225.45     4901.79       6127.24
  LUBE OIL                            726.00        726.00       726.00        726.00        726.00       726.00     2904.00       3630.00
  (LABOR)                           11812.50      11812.50     11812.50     11812.50      11812.50      11812.50    47250.00      59062.50
  OPERATIONS AND MAINTENANCE         5050.00       5050.00      5050.00       5050.00       5050.00      5050.00    20200.00      25250.00
  TOTAL RECURRING COSTS              7001.44      24411.10     24411.10     24411.10      24411.10      24411.10    28005.77     35007.21
  ENERGY SAVED - KEROSENE            4360.50       4360.50      4360.50       4360.50       4360.50      4360.50    17442.00      21802.50
                 FIREWOOD            240.00       240.00        240.00        240.00       240.00       240.00       960.00       1200.00
  INCREASED AGRI PRODUCTIVITY        5225.00       5225.00      5225.00       5225.00       5225.00      5225.00    20900.00      26125.00
  SURPLUS ENERGY INTO DIESEL            0.00          0.00         0.00          0.00          0.00         0.00        0.00          0.00
                        ELEC Y          0.00          0.00         0.00          0.00          0.00         0.00        0.00          0.00
  REVENUE  FROM COMM OPNS              0.00         0.00          0.00          0.00         0.00         0.00         0.00          0.00
  TOTAL ANNUAL BENEFITS              9738.09       9738.09      9738.09       9738.09       9738.09      9738.09    38952.34     48690.43
  + SALE OF SURPLUS GAS) + .9811
  + OPERATIONS & MAINTENANCE)        2736.64    -14673.01    -14673.01      -14673.01    -14673.01    -14673.01    10946.58      13683.22
  NET PRESENT WORTH (15 YEARS):    -39181.57
  ((SALE OF SURPLUS GAS + 791.001
  + LABOR + OP. & MAINTENANCE)     -18037.97     -35447.63    -35447.63      -35447.63    -35447.63    -35447.63   -72151.88     -90189.81
                                                MODEL 2:  COOKING, LIGHTING & INDUSTRY
                                       D =  506255.00   R =      0.00     P_DS = 0.00   R_LC = 0.04
   D =    506255.000     G =        0.041              11812.500     N LC =    5.000      P_LC =   10.000   
   D L =     273.750     G_C = 11425.000      LO_L =      43.800     P =    10000.000      R =       0.000
   D_LC =  22107.100     G_L =   2300.000     LO_F =      4.800      P_D =     2.700     R_LC =     0.040
   D_P  =     30.120      G_P =   253.000     LO_RC =                      
                                                         0.000      P_DS =    0.000
   C_RC =    150.000     G_RC = 1260.000      M =      4800.000     P_FW =     0.040
   E =     41000.000     IA =    8100.000      N =         0.000      P_K  =    2.250
YEAR                                        1             2            3           4            5            6           7-10           11-15
  LOAN AMORTIZATION                         0.00     16419.59     16419.59     16419.59     16419.59    16419.59          0.00            0.00
  ENERGY (DIESEL)                        1225.45      1225.45      1225.45      1225.45      1225.45     1225.45       4901.79         6127.24
  LUBE OIL                                726.00        726.00       726.00       726.00      726.00       726.00        2904.00        3630.00
  (LABOR)                               11812.50      11812.50     11812.50     11812.50     11812.50    11812.50      47250.00        59062.50
  OPERATIONS AND MAINTENANCE             5050.00       5050.00      5050.00      5050.00      5050.00     5050.00      20200.00        25250.00
  TOTAL RECURRING COSTS                  7001.44      23421.03      23421.03    23421.03    23421.03     23421.03       28005.77       35007.21
  ENERGY SAVED - KEROSENE               4360.50       4360.50       4360.50     4360.50     4360.50      4360.50       17442.00       21802.50
                 FIREWOOD                 240.00        240.00        240.00      240.00      240.00       240.00         960.00        1200.00
  INCREASED AGRI PRODUCTIVITY            8100.00       8100.00      8100.00     8100.00      8100.00      8100.00      32400.00       40500.00
  SURPLUS ENERGY INTO DIESEL                0.00          0.00         0.00         0.00         0.00        0.00          0.00            0.00
                      ELEC Y                0.00          0.00         0.00         0.00         0.00        0.00          0.00            0.00
  REVENUE FROM COMM OPNS                    0.00          0.00          0.00        0.00        0.00         0.00          0.00           0.00
  TOTAL ANNUAL BENEFITS                 12613.09      12613.09      12613.09    12613.09    12613.09     12613.09       50452.34       63065.43
+ OPERATIONS & MAINTENANCE)             5611.64    -10807.94     -10807.94    -10807.94   -10807.94   -10807.94       22446.58        28058.22
NET PRESENT WORTH (15 YEARS):         -13902.12
+ LABOR + DP. & MAINTENANCE)          -13037.57    -34457.55     -34457.55    -34457.55   -34457.55   -34457.55       -72151.66      -90185.61
                                                MODEL 2:  COOKING, LIGHTING & INDUSTRY
                                      O =   506255.00    R =    0.00   P_OS = 0.00  R_LC = 0.10
   O =   506255.000     G =        0.047      L =    11812.500      N_LC =  5.000     P_LC =   10.000 
   O_L =    273.750     G_C = 11425.000      LO_L =    43.800     P   =10000.000      R =      0.000
   O_LC = 22100.000      G_L =  2300.000      LC_P =      4.800     P_D =    2.700     R_LC =   0.100
   O_P =     30.120     G_P =    253.000     LC_RC =    0.000      P_DS =  0.000
                                                       0.000      P_FW =  0.040
   O_RC =   150.000     G_RC = 1260.000      M =     4800.000
   E =    41000.000     1A=     8100.000      N =        0.000      P_K =   2.250
YEAR                                1           2          3         4          5          6         7-10         11-15
  LOAN AMORTIZATION                 0.00    19282.51  19282.51  19282.51   19282.51  19282.51        0.00         0.00
  ENERGY (DIESEL)                1225.45    1225.45   1225.45    1225.45   1225.45   1225.45      4901.79      6127.24
  LUBE OIL                        726.00     726.00    726.00     726.00    726.00    726.00      2904.00      3630.00
  (LABOR)                       11812.50   11812.50  11812.50   11812.50  11812.50  11812.50     47250.00     59062.50
  OPERATIONS AND MAINTENANCE     5050.00    5050.00   5050.00    5050.00   5050.00   5050.00     20200.00     25250.50
  TOTAL RECURRING COSTS          7001.44    26283.95  26283.95   26283.95  26283.95  26283.95     28005.77     35007.21
  ENERGY SAVED - KEROSENE        4360.50     4360.50   4360.50    4360.50   4360.50   4360.50     17442.00     21802.50
                 FIREWOOD         240.00      240.00    240.00     240.00    240.00    240.00       960.00      1200.00
  INCREASED AGRI PRODUCTIVITY    8100.00    8100.00   8100.00    8100.00   8100.00   8100.00     32400.00     40500.00
  SURPLUS ENERGY INTO DIESEL        0.00        0.00      0.00       0.00      0.00      0.00         0.00         0.00
                       ELEC Y       0.00        0.00      0.00       0.00       0.00      0.00         0.00         0.00
  REVENUE FROM COMM OPNS            0.00       0.00       0.00       0.00      0.00       0.00         0.00        0.00
  TOTAL ANNUAL BENEFITS         12613.09    12613.09  12613.09   12613.09  12613.09  12613.09     50452.34     63065.43
+ OPERATIONS & MAINTENANCE)     5611.64   -13670.87 -13670.87 -13670.87 -13670.87 -13670.87    22446.58     28058.22
+ LABOR + OP. & MAINTENANCE)  -18037.97   -37320.48 -37320.48 -37320.48 -37320.48 -37320.48   -72151.88    -90189.81
                                                MODEL 3:  LIGHTING & INDUSTRY
                                        O =  86021.00   R =     0.00   P_DS = 0.00  R_LC = 0.04
   O =    86121.000     G =        0.041      L =    11812.500      N_LC = 5.000      P_LC =  10.000     
   O_L =    273.750     G_C =      0.000     LO_L =    43.800      P =    0.000     R =       0.000
   O_LC =  4500.000     G_L =   2300.000     LO_F =     4.800      P_D =  2.700     R_LC =    0.040
   O_P =     30.120     G_P =    253.000     LO_RC =                        
                                                       0.000      P_DS = 0.000
   O_RC =   150.000     G_RC = 1260.000      M =     4807.000     P_FW = 0.020
   E =    41000.000     IA =   1376.000     N =        0.000      P_K =  2.250 
YEAR                                       1           2          3         4         5          6         7-10        11-15
  LOAN AMORTIZATION                        0.00   10220.13  10220.13   10220.13 10220.13   10220.13       0.00         0.00
  ENERGY (DIESEL)                       1225.45    1225.45   1225.45    1225.45  1225.45   1225.45     4901.79      6127.24
  LUBE OIL                               726.00      726.00    726.00     726.00   726.00    726.00     2904.00      3630.00
  (LABOR)                              11812.50    11812.50  11812.50   11812.50 11812.50   11812.50   47250.00     55062.50
  OPERATIONS AND MAINTENANCE            5050.00     5050.00   5050.00    5050.00  5050.00   5050.00    20200.00    25250.00
  TOTAL RECURRING COSTS                 7001.44    17221.57  17221.57  17221.57 17221.57   17221.57   28005.77    35007.21
  ENERGY SAVED - KEROSENE               4360.50     4360.50   4360.50   4360.50   4360.50   4360.50   17442.00     21802.50
                 FIREWOOD                120.00      120.00    120.00    120.00    120.00    120.00     480.00       600.00
  INCREASED AGRI PRODUCTIVITY           1376.00     1376.00   1376.00    1376.00  1376.00   1376.00     5504.00      6880.00
  SURPLUS ENERGY INTO DIESEL               0.00        0.00      0.00       0.00     0.00      0.00        0.00         0.00
                        ELEC Y             0.00        0.00      0.00       0.00     0.00      0.00        0.00         0.00
   REVENUE FROM COMM OPNS                   0.00       0.00      0.00       0.00     0.00      0.00        0.00         0.00
  TOTAL ANNUAL BENEFITS                 5771.36     5771.36   5771.36   5771.36   5771.36   5771.36   23085.45     28856.82
+ OPERATIONS & MAINTENANCE)           -1230.08  -11450.20 -11450.20 -11450.20 -11450.20 -11450.20  -4920.31    -6150.89
NET PRESENT WORTH (15 YEARS):        -44576.51
+ LABOR + OP. & MAINTENANCE)         -18087.97  -28258.09 -28258.09 -28258.09 -28258.09 -28258.09  -72151.88   -90189.81
                                                MODEL 3:  LIGHTING & INDUSTRY
                                         O = 86071.00   R.       0.00  P_DS = 0.00    R_LC = 0.10
   O =      86021.00     G =        0.047      I =    11812.500      N_LC =  5.000     P_LD = 10.000
   O_L =     273.750     G_C =      0.000     LO_L =    43.800      P =     0.000     R =      0.000
   O_LC =   4500.000     G_L =   2300.000     LO_P =     4.800      P_D =   2.100     R_LC =   0.100
   O_P =      30.120     G_P =    253.000     LO_RC =              P_DS =   0.000
                                                        0.000      P_FW =  0.020
   O_RC =    150.000     G_RC = 1260.000      M =     4800.000     P_K =    2.250
   E =     41000.000     IA =    1376.000      N =        0.000
YEAR                                        1           2           3          4            5           6         7-10        11-15
  LOAN AMORTIZATION                         0.00   12002.11   12002.11    12002.11    12001.11   12002.11         0.00         0.00
  ENERGY (DIESEL)                        1225.45    1225.45    1225.45     1225.45      1225.45    1225.45      4901.75      6127.24
  LUBE OIL                                726.00      726.00     726.00      726.00       726.00     726.00      2904.00      3630.00
  (LABOR)                               11812.50    11812.50   11812.50    11812.50    11812.50   11812.00     47250.00     59062.50
  OPERATIONS AND MAINTENANCE             5050.00     5050.00    5050.00     5050.00      5050.00    5050.00     20200.00     25250.00
  TOTAL RECURRING COSTS                  7001.44    19003.55   19003.55   19003.55     19003.55   19003.55    28005.77     35007.21
  ENERGY SAVED - KEROSENE                4360.50     4360.50    4360.50    4360.50      4360.50     4360.50    17442.00     21802.50
                 FIREWOOD                 120.00      120.00      120.00     120.00       120.00      120.00      480.00       600.00
  INCREASED AGRI PRODUCTIVITY            1376.00     1376.00    1376.00     1376.00      1376.00    1376.00      5504.00      6880.00
  SURPLUS ENERGY INTO DIESEL                0.00        0.00       0.00        0.00         0.00       0.00         0.00         0.00
                       ELEC Y               0.00        0.00       0.00        0.00         0.00       0.00         0.00         0.00
  REVENUE FROM COMM OPNS                    0.00        0.00        0.00       0.00         0.00        0.00        0.00         0.00
  TOTAL ANNUAL BENEFITS                  5771.36     5771.36    5771.36    5771.36      5771.36     5771.36    23085.45     28856.82
+ OPERATIONS & MAINTENANCE)            -1230.08  -13232.19   -13232.19  -13232.19   -11232.19    13232.19    -4920.31    -6150.35
NET PRESENT WORTH (15 YEARS):         -50717.55
((SALE OF SURPLUS GAS) + 791.001
+ LABOR + OP. & MAINTENANCE)          -18037.51  -30040.08   -30040.08  -30040.08   -30040.08   -30040.08  -72151.88    -90189.81
                                                MODEL 3:  LIGHTING & INDUSTRY
                                         D=  506255.00   R =    0.00  P_DS = 0.00    R_LC = 0.04
   O =   506255.000     G =       0.041      L =     11812.500      N_LC = 5.000      P_LC = 10.000  
   O_L =    273.750     G_C =     0.000     LO_L =     43.800      P =    0.000     R =      0.000
   D_LC = 22100.000      G_I = 2300.000     LO_F =      4.800      P_D =  2.700      R_LC=   0.040
   O_P =     30.120     G_P =   253.000     LO_RC =                         
                                                       0.000      P_DS = 0.000
   O_RC =   150.000     G_RC= 1260.000      M =      4800.000     P_FW = 0.020
   E =    41000.000     IA =   8100.000     N =         0.000      P_K =  2.250
YEAR                                      1           2           3          4           5           6          7-10          11-15
  LOAN AMORTIZATION                       0.00  14173.41    14173.41    14173.41   14173.41    14173.41          0.00           0.00
  ENERGY (DIESEL)                      1225.45   1225.45     1225.45     1225.45    1225.45    1225.45       4901.79         6127.24
  LUBE OIL                              726.00     726.00      726.00      726.00      726.00     726.00       2904.00         3630.00
  (LABOR)                             11812.50   11812.50    11812.50    11812.50   11812.50   11812.50      47250.00        59062.00
  OPERATIONS AND MAINTENANCE           5050.00    5050.00     5050.00     5050.00    5050.00    5050.00      20200.00        25250.00
  TOTAL RECURRING COSTS                7001.44   21174.85    21174.85   21174.85    21174.85   21174.85     28005.77        35007.21
  ENERGY SAVED - KEROSENE              4160.50    4360.50     4360.50     4360.50    4360.50    4360.50      17442.00        21802.50
                 FIREWOOD               120.00     120.00      120.00      120.00      120.00     120.00        480.00          600.00
  INCREASED AGRI PRODUCTIVITY          8100.00    8100.00     8100.00     8100.00    8100.00    8100.00      32400.00        40500.00
  SURPLUS ENERGY INTO DIESEL              0.00       0.00        0.00        0.00        0.00       0.00          0.00            0.00
                       ELEC Y             0.00       0.00         0.00        0.00       0.00        0.00          0.00           0.00
  REVENUE FROM COMM OPNS                  0.00       0.00         0.00       0.00        0.00        0.00         0.00           0.00
  TOTAL ANNUAL BENEFITS               12495.36   12495.36    12495.36   12496.36    12496.36   12496.36     49981.45        62476.82
+ OPERATIONS & MAINTENANCE)           5493.92  -8679.98     -8679.48   -8679.48   -8679.48    -8679.48       21975.69      27469.61
NET PRESENT WORTH (15 YEARS):        -7056.68
((SALE OF SURPLUS GAS) + 791.001
+ LABOR + OP. & MAINTENANCE)        -18037.57 -32211.38   -32211.38    -32211.38 -32211.38   -32211.38      -72151.88     -90189.81
                                  MODEL 3 :  LIGHTING & INDUSTRY
                         D = 506255.00   R =     0.00  P_0S = 0.00 R_LC = 0.10
   D=    506255. 00        G=         0.041     L=    11812.500      N_LC=     5.000    P_LO=    10.000
   O_L=     273.750        G_C=       0.000    LO_L=    43.800      P=        0.000     R=       0.000
   O_LC=  22100.000        G_L=    2300.000    LC_F=     4.800      P_D=      2.700    R_LC=     0.100
   O_P=      30.170        G_P=     253.000    LC_RC=
                                                        0.000      P_DS=     0.000
   O_BC=    150.000        G_RC=   1260.000    M=     4300.000      P_PW=     0.020
   E=     41000.000        L =     8100.000     A=        0.000      P_X=      2.250
YEAR                                  1          2          3         4          5        6         7-10       11-15
LOAN AMORTIZATION                    0.00  16644.68   16644.68  16644.68  16644.68   16644.68       0.00      0.00
ENERGY (DIESEL)                   1225.45    1225.45   1225.45   1225.45    1225.45   1225.45   4901.79    6127.24
LUBE OIL                            726.00     726.00    726.00    726.00     726.00    726.00   2904.00    3630.00
                                 11812.50   11812.50  11812.50  11812.50   11812.50  11812.50  47250.00   59062.50
OPERATIONS AND MAINTENANCE        5050.00    5050.00   5050.00   5050.00    5050.00   5050.00  20200.00   25250.00
TOTAL RECURRING COSTS             7001.44   23646.13  23646.13  23646.13   23646.13  23646.13  28005.77   35007.21
  ENERGY SAVED - KEROSENE          4360.50    4360.50   4360.50    4360.50   4360.50   4360.50   17442.00  21802.50
                 FIREWOOD           120.00     120.00    120.00     120.00    120.00    110.00     480.00    600.00
INCREASED AGRI PRODUCTIVITY       8100.00    8100.00   8100.00   8100.00    8100.00   8100.00  32400.00   60500.00
SURPLUS ENERGY INTO DIESEL           0.00       0.00       0.00      0.00       0.00       0.00      0.00       0.00
                     ELECY            0.00       0.00      0.00       0.00       0.00      0.00       0.00       0.00
REVENUE FROM COMM OPNS               0.00       0.00       0.00      0.00       0.00       0.00      0.00       0.00
TOTAL ANNUAL BENEFITS            12495.66   12495.36  12495.36  12495.36   12495.34  12495.36  49981.45   62476.32
* OPERATIONS & MAINTENANCE)       5493.92 -11150.76 -11150.76 -11150.76 -11150.16 -11150.76   21915.65  27469.61
NET PRESENT WORTH (15 YEARS):   -1557 .17
* LABOR * OP. & MAINTENANCE)    -18037.57 -34682.65 -34682.65 -34682.65 -34682.65 -34682.65 -78151.89 -90189.81
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