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                          TECHNICAL PAPER #31
                       UNDERSTANDING BRIQUETTING
                          Mac Cosgrove-Davies
                          Technical Reviewer
                            Dr. Ben Bryant
                             Published By
                   1600 Wilson Boulevard, Suite 500
                     Arlington, Virginia 22209 USA
                 Tel: 703/276-1800 . Fax: 703/243-1865
                       Understanding Briquetting
                          ISBN: 0-86619-233-6
              [C]1985, Volunteers in Technical Assistance
This paper is one of a series published by Volunteers in Technical
Assistance to provide an introduction to specific state-of-the-art
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their situations.
They are not intended to provide construction or implementation
details.  People are urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
The papers in the series were written, reviewed, and illustrated
almost entirely by VITA Volunteer technical experts on a purely
voluntary basis.  Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.  VITA staff included Maria Gianuzzi as
editor, Suzanne Brooks handling typesetting and layout, and
Margaret Crouch as project manager.
The author of this paper, VITA Volunteer Mac Cosgrove-Davies, is
a mechanical engineer currently working for the Carl T. Jones
Corporation in Springfield, Virginia.   He has traveled in Central
and South America and has a keen interest in appropriate energy
technology.  The reviewer is also a VITA Volunteer.  Dr. Ben Bryant
is the professor of wood and fiber utilization technology at the
College of Forest Resources, University of Washington, Seattle,
and president of AFPITA, a non-profit technology transfer company.
In addition to teaching and research in the forest products
field, he has invented structural building panels made of
wood and fiber, consulted extensively in the forest products
industries, and performed studies in 22 developing countries in
the area of approporiate technology transfer.   His group developed
the compound lever briquetting press.
VITA is a private, nonprofit organization that supports people
working on technical problems in developing countries.   VITA
offers information and assistance aimed at helping individuals
and groups to select and implement technologies appropriate to
their situations.  VITA maintains an international Inquiry Service,
a specialized documentation center, and a computerized
roster of volunteer technical consultants; manages long-term
field projects; and publishes a variety of technical manuals and
                 By VITA Volunteer Mac Cosgrove-Davies
In many parts of the world, the primary source of energy for such
vital activities as cooking and space heating is burning wood and
other agricultural products.   An increasing population using a
dwindling resource of combustible biomass materials will eventually
result in a shortage of those materials unless steps are
taken to reverse the trend.
One means of making more efficient use of existing resources is
through the use of briquetting.   Briquetting involves collecting
combustible materials that are not usable due to a lack of density,
and compressing them into a solid fuel of a convenient
shape that can be burned like wood or charcoal.   Materials such as
sawdust, wood bark, rice husks, and straw have been successfully
During the first and second World Wars, households in several
European countries employed a simple lever-operated briquetting
press that used soaked waste paper and other combustible domestic
waste as a feed stock.  Today's industrial briquetting machines,
although much larger and more complex, operate on the same general
Although briquetting has been widely used in the metallurgical
industry to recover metal filings, shavings, and scraps that
would otherwise be of little value, this paper is concerned
solely with the briquetting of combustible materials for fuel.
The focus is on simple technologies that can be employed on a
small to intermediate scale.
Briquetting is one of several compaction technologies in the
general category of densification.   In densification, a material
is compressed to form a product of higher bulk density, lower
moisture content, and uniform size, shape, and material properties.
There are two ways that compaction can be accomplished:
with and without a binder.
One must have something to make the material stick together
during compression.  Otherwise, when the briquette is removed from
the mold, it will crumble to pieces.   This fastening agent is
known as a binder.  In some cases, most commonly under high temperature
and/or pressure, a material can act as its own binder.
Wood, for example, becomes plastic and can be briquetted without
a binder under such conditions.   Many of the processes considered
here, however, will require the addition of a binder.
In most cases, the process of briquetting will consist of a
series of steps:
     1.   Collecting material to be densified
     2.   Preparing material
     3.   Compacting
     4.   Removing, drying or cooling, and storing
As mentioned above, there is a wide variety of materials that can
be densified.  Some can be bundled, <see figure 3> or tied together, rather than
briquetted.  A partial list is included below.
     o   jute              o  rice husks          o   coffee husks
     o   coal dust         o  alfalfa              o  some nut shells
     o   sisal             o  bagasse              o   dung
     o   wood wastes       o  straw                o   vines
        - shavings       o   paper waste          o  municipal waste
        - sawdust        o   peat                 o  sunflower husks
        - bark            o  olive  residue       o  fish waste
        - twigs           o  hemp                o   coconut dust
     o   coconut fiber     o  peat                 o   cotton sowing
        (coir)            o  food  processing     o  leather waste
                            waste               o   charcoal fines
It should be noted that the use of industrial or automotive waste
oils should be avoided since in many cases such oils contain
additives that can give off toxic fumes when burned.  If such oil
waste is to be used, it should be thoroughly checked by a competent
laboratory first.
In general, any material that will burn but is not in a convenient
size, shape, or form to be readily usable as fuel is a good
candidate for briquetting.  It may be necessary or desirable to
make briquettes of more than one material.
Once the raw material is collected, it must be assembled in a
central location for processing.   The method of preparation depends
somewhat on the particular material being briquetted, but
the procedure generally includes some or all of the following
The raw material is first reduced in size by chopping, crushing,
breaking, rolling, hammering, milling, grinding, cutting, etc.,
until it can pass through a screen or reaches a suitably small
and uniform size.  Since this process consumes a good deal of
energy, this size reduction step should be as short as possible.
Indeed, with some materials this step may not even be necessary.
Although the feed stock fed to the briquetting press is often
wet, it may still be necessary to dry the stock before mixing it
with the binder.  Drying can be done in the sun, with a heater, or
by using heated air and a rotating drum.   You can dry the material
before or after size reduction.
The method of mixing the raw material with the binder to produce
a feed stock can vary widely.   Anything from a simple trough and
hoe to a modified commercial cement mixer can be used.   A ribbon
mixer for small-scale production is shown in Figure 1.
You must determine the correct propportion of raw material to
binder before starting full-scale production.   This is best accomplished
by a trial and error method of making several briquettes
with different mixtures of binder material, then testing
each for mechanical strength and burning properties.
The cost of the binding material can be critical to the economic
success of the project, so the smallest amount of binder necessary
for an acceptable briquette should be used.   Although a
combustible binder is desirable, it is possible to use a noncombustible
binder with good results.  Alternative uses of the
binder must be weighed against the value of the final product as
an energy source.  The following is a partial list of binding
  Combustible Binders           Non-combustible binders
     o   natural or synthetic         o slime
        resins                       o clay
     o   tar                          o mud
      o  animal manure               o cement
     o   sewage mud
     o   fish waste
     o   algae
     o   starch
In carbonization, a biomass material (usually wood) is heated to
very high temperatures but is not given enough oxygen for the
material to burn.  This processs produces charcoal.
The briquetting process can be used with carbonization to produce
briquettes made wholly or partially of charcoal.   The briquettes
can be made using charcoal fines or ash as part of the feed
stock, or the briquettes can be compacted with any of the raw
materials listed above and then carbonized.   The first method wil
probably produce a more consistent product.   The second method
may result in briquettes that are too fragile to handle without
creating excessive dust.
The next step, compaction, can be done in many ways.   The following
section on design variations will describe several possibilities.
A basic overview is given below.
In general, a supply of prepared feed stock is loaded into a
chamber, the chamber is covered with a close-fitting top, and
pressure is applied to compress the feed stock.   The pressure
applied can be anywhere from 0.5 to 1,200 kilograms per square
centimeter (kg/sq cm) depending on the process employed.  In some
cases, the feed stock is heated to aid in the binding.
Another method of compaction, employed by some of the more sophisticated
briquetting machines, is to heat the feed stock and
then extrude it.  Extrusion is a process whereby the feed stock is
forced through a small opening at high pressure.   The result is a
continuous log that can be cut to any length.   The advantage of
extrusion is that it is a continuous process that can produce
briquettes in many shapes and sizes.   Disadvantages include the
need for high pressure, temperature, and energy consumption, as
well as the relatively complex machinery involved (see Figure 2).
A handful of soaked paper or other feed stock is taken from the
mixing vat and hand-molded into spherical briquettes.   In some
areas, dung is shaped by hand for use as fuel.   Formed briquettes
are sun dried before use.  These briquettes will burn longer if
wood ash containing some charcoal is added to the feed stock.
This is the first of the briquetting presses.   It utilizes a
mechanical lever to apply greater pressure than is possible with
hand molding.  This press also utilizes waste paper.  Soaked paper,
preferably with wood ash added, is put in the mold and pressed.
Briquettes are then removed and sun dried.   Finished briquettes
are spherical, about 5 cm in diameter and weigh about 30 grams.
This press provides greater compaction than the Wrought Iron
Press I because the compression face is pressed deeper into the
mold form.  The basic press is again easy to make, taking approximately
four to five hours and five to eight kg of iron.   The
length of the lever arm will determine the briquetting pressure.
The mold should be sturdy enough to handle the pressure created
by the lever.  Any of the briquetting materials given above can be
used in this press.  Modifications can also be made to yield
different shapes depending on the skill of the manufacturer.
Briquetting feed stock is poured into the mold and the lever is
pushed down, compressing the briquette.   The lever is then lifted,
the base plate removed, and the finished briquette is pushed
through and then placed in the sun to dry.
Metal or plastic pipe provides a good briquetting mold since it
produces cylindrical briquettes.   The tube presses illustrated
(see Figure 4) consist of a tube mounted vertically on a platform

ubr4x7.gif (600x600)

and a close fitting ram used for compaction.   The basic design can
be varied considerably, as the figure indicates.
Feed stock is poured into the tube and compressed with the ram.
The tube is then positioned over a hole (or a slide is removed)
below the tube exposing a hole) and the briquette is pushed
through.  Briquettes are then dried in the sun before storage and
Presses currently in use for making stabilized earth blocks might
be modified to make briquettes from a mixture of a clay binder
and charcoal dust or coal dust.   The Combustaram, similar to the
CINVA-Ram and Tersaram, is commercially available or can be
manufactured locally (see Figure 5).

ubr5x8.gif (600x600)

The lever arm is put in the open position, feed stock is poured
into the molds and the lever is then quickly pushed up, over the
top of the press, and down.  This movement positions the top of
the press and compresses the briquettes on the downward stroke.
The lever is then moved back to the original position and again
pushed down, thus forcing the briquettes out of the molds.  Finished
briquettes are set in the sun to dry.   The process requires
at least two workers.
This press incorporates the principles of both the wrought iron
briquetting press and the tube press.   Made of wood, the compound
lever multiplies the effectiveness of a simple lever.   Enough
pressure is generated when chopped, biodegraded, or finely
divided fibrous material is used in the damp or wet state to
eliminate the need for a binder.
The filled mold with the plunger inserted is initially placed
toward the rear of the main lever to take advantage of the maximum
stroke.  After initial compaction, the mold is moved to the
forward position for final pressure application.   The mold is
perforated to allow for escape of excess fluids, and a dowel in
the face of the mold assembly places a center hole, improves
combustion of the briquette.
This device is designed specifically to make fuel logs from rice
husks.  The extruder, powered by a 20 HP electric motor, works
best with husks that have been ground and/or dried to reduce
moisture content.  The device measures 1.5 x 2.75 x 1.1 meters,
requires one or two workers, and produces 150 kgs of fuel logs
per hour.  The rice husk fuel log extruder is relatively new and
has not yet been manufactured outside of Thailand.
Once the device is warmed up, the operator must keep the machine
continuously supplied with prepared husks.   The operator must also
stack the finished logs and monitor the temperature of the device's
heating unit.  The machine is designed to operate 24 hours
a day.  Because of the large volume of rice husks required to
keep the machine in continuous operation, this device may be
best-suited to large rice processing centers.
Industrial briquetting machines densify waste produced in an
industrial setting.  These machines produce a wide variety of
products--briquettes, pellets, cubes, logs.   Quite often, machines
used for producing animal feed pellets can be modified for fuel
pellets.  Many do not require binding materials.  In addition,
several manufacturers offer a consulting service to determine
which of their models is most appropriate for a particular application.
Manufacturers should be contacted for more information on
their products.
Briquetting or densification is only one of several technologies
that should be considered for the use of agricultural and biomass
waste.  Alternatives include:
1.  Fertilizer or Soil Conditioner: The use of biomass waste for
energy production can deprive the soil of important conditioning
agents, and the long-term impact of this deprivation must be
carefully studied.
2.  Livestock Feed: In some cases, the potential briquetting
material could be used as food for local livestock that could be
used as a source of food or as work animals.
3.  Bacterial Fermentation for Alcohol Production:  In aerobic
fermentation, bacteria act to break down organic materials in the
presence of oxygen.  This process can produce alcohol, which is an
attractive fuel because of its high energy content.   It is also a
liquid and therefore relatively easy to handle.   Research into
fermentation has progressed rapidly in the past several years.
The economics of alcohol production favor large-scale facilities
and this technology is not recommended on the village scale.
4.  Anaerobic Digestion for Methane Production: Anaerobic digestion
differs from aerobic digestion in that in anaerobic digestion
the bacteria acts in the absence of oxygen.   The product of
anaerobic digestion is methane, a high-heat, clean-burning flammable
gas similar to natural gas.  However, it requires a relatively
large initial investment in equipment and special storage
and handling, as well as a gas-burning stove.   Several countries,
notably China and India, have developed simple small-scale
5.  Gasification: When a combustible material is raised to a very
high temperature without sufficient oxygen for combustion to take
place, reactions occur that produce a combustible gas, liquid
products, and charcoal or ash.   These processes of thermal decomposition
are known as gasification, pyrolysis, and carbonization
respectively.  Gasification can be performed on biomass
waste, but in general it requires a large-scale operation to be
economically feasible.
6.  Pyrolysis:   As mentioned above, pyrolysis is the process of
producing a liquid when a combustible solid is heated without
enough oxygen for complete combustion.   Large-scale plants exist,
and pyrolysis can also be performed on a small scale in conjunction
with a retort for making charcoal.   The products of
pyrolysis, such as oils, tars, and resins, are useful in various
industrial, commercial, and household applications.
7.  Suspension Burners: These are burners in which ground combustible
materials are mixed with air blowing up from the bottom of
a combustion chamber and burned in suspension.   They effectively
supply a relatively clean, hot gas than can be used in dry kilns,
power boilers, veneer dryers, and other processes.   They are not
recommended for household use, but may be appropriate in a light
industrial setting.
8.  Fluidized Bed Combustors:  In a fluidized bed combustor, air
is blown up from the bottom of the combustion chamber, but in
this case the combustion chamber is partially filled with a
granular material such as sand.  The air being forced up through
the sand circulates the sand as it if were "boiling." When
combustion takes place in this system, the sand acts as a bed on
and in which the combustible material burns.   This system is more
flexible than the suspension burner because the feed stock need
not be finely ground or even of a consistent size.   Fluidized bed
combustors also represent a proven technology and are appropriate
in light industrial settings.
Before embarking on a briquetting program, investigate the potential
market to determine the viability of the project.   Social,
environmental, political, and economic factors should be researched
along with technical matters.   Many projects have failed
because the non-technical factors in their involved were neglected.
For example, although in some cases the raw materials required
for briquetting will be very low in cost, the market for briquettes
itself will increase the value of the raw materials.
This could have negative effects on the distribution of income.
In addition, some briquetting materials have competing uses.
Dung, for example, is also used as a fertilizer.   Thus the value
of the fuel for its various uses must be weighed before any
decision is made.  Further, there are usually several ways of
producing energy from the raw material.
A special note with respect to the stove that will be used: In
general, the final briquetted product has a heating value comparable
to wood.  It may, however, burn in a different manner than
traditional fuels and thus the stove (or the briquette) may have
to be modified to be compatible.   This issue should be taken
quite seriously by the briquette manufacturer who plans to sell
the product on the open market.
When analyzing the feasibility of a briquetting project and the
market appeal of the product, some preliminary research is
essential before proceeding with technical design.   The most
effective way of achieving success is to assess the situation
from several viewpoints--forestry administration, farmers' cooperatives,
women's associations, contractors, technicians, etc.
These groups are a good source of information about the availability
of combustible waste of all kinds, the social climate,
the attitudes of local people to innovations, and economic and
other relevant factors.
Environmental questions should also be taken into consideration,
because using biomass waste as fuel eliminates an important
element in the ecological chain.   Normally, biomass waste is
returned to the soil.  If this balance is broken, the consequences
may decrease productivity of the soil and, in extreme
conditions, even lead to desertification.
The analysis should include information on:
     1.   Cultural habits pertinent to food preparation and
         cooking styles
     2.   Size of the market: number of people and amount of fuel
     3.   Relevant social factors
     4.   The history of previous innovations in local society
     5.   The willingness and ability of people to pay for the
         new fuel product
     6.   Types and requirements of stoves in use in the market
     7.   Availability and characteristics of biomass waste in
         the region
     8.   Environmental considerations
     9.   Transportation problems
    10.   Availability of credit or subsidy to get the enterprise
 The briquetting of biomass waste that would otherwise be unavailable
as fuel can be an effective, low-cost method of increasing
the fuel supply.  In addition, by providing an alternative to
wood burning, briquetting can help slow the process of deforestation.
A wide range of technologies makes briquetting accessible
to nearly everyone.  Finally, briquetting holds a unique place
among the various alternative uses of biomass with its easily
understandable technology and its simplicity of operation.
Agnew Environmental Products
Box 1168
Grants Pass, Oregon 97526
Telephone: 503/479-3396
Bio-Solar Corp.
P.O. Box 762
Eugene, Oregon 97401
800 Lake St.
Kent, Ohio 44240
California Pellet Mill Co.
1800 Folsom St.
San Francisco, California 94103
Deere & Co. (formerly John Deere)
John Deere Rd.
Moline, Illinois 61265
467 Eureka Rd.
Wyandotte, Michigan 48192
Fourply Inc.
P.O. Box 890
Grants Pass, Oregon 97526
Guaranty Performance Co. Inc.
P.O. Box 748
Independence, Kansas 67301
Hobbs (C.B.) Co.
Elk Grove, California 95624
Papakube Corp.
7185 Navajo Rd.
Suite 1
San Diego, California 92119
Sprout Waldron
802 Logan St.
Muncy, Pennsylvania 17756
Ferdinand Platbrood
12 Category des Rossignols
6070 Chatlet
Fred Hausmann Ltd.
4005 Basel
Hawker Siddeley Canada Inc. (formerly Ltd.)
7 King St., East
Toronto, Canada M5C1A3
Mr. Sayan Panpinig
53 MOO. 6 A. Ladkrabang
Bangkok, Thailand