Appendix V

Planning Scheme for the Lay Out of a Biogas Plant (1

Step 1: establish gas requirement
Guide values for gas consumption

Cooking: 0.25 m³ (8 cu ft) per person per day
Lighting: 0.12-0.15 m³ (4-5 cu ft) per hour per lamp
Driving engines: 0.75 m³ (17 cu ft) per kW per hour

Gas requirement per unit x No. of units = Total gas requirement

Example: 0.25 m³ per person and per day X _4_ persons =__1.0__m³

Gas requirement for cooking: 0.25 m³ per person per day X _________persons =__________m³
Gas requirement for lighting: 0.15 m³ per lamp per hour X ___________lamps =___________m³
Gas consumption of engines: 0.75 m³ per kW per hour X ________operating hours = ______m³

Gas requirements for other processes: _________X__________=__________m³

- Refrigeration _________X__________=__________m³
- Drying plant _________X__________=__________m³
- Production __________m³
Total gas requirement per day

Is this gas requirement likely to satisfy needs in 5 years?

Z Additional gas requirement _________X__________=__________m³

Total gas requirement _____________m³

Step 2: establish gas production
Gas generation - guide values

Type	Manure (moist) per day	Gas per kg per day	Gas yield per animal
1 head of cattle	10 kg	361(1.3 cu ft)	3601(13 cu ft)
1 water buffalo	15 kg	361(1.3 cu ft)	5401(19.5 cu ft)
1 pig (approx. 50 kg)	2.25 kg	781(2.8 cu ft)	1801(6.3 cu ft)
1 chicken (approx. 2 kg)	0.18 kg	62 1(2.2 cu ft)	11.21 (0.4 cu ft)
Adult human excrete	0.4 kg	701(2.5 cu ft)	281(1 cu ft)

Gas yields refer to material with its natural moisture content.

For the final design of a biogas plant the use of specific literature e.g. 131, [4], [5], [6] is recommended, likewise the consultation of a biogas expert if available.

Actual production
Fertilizer production Gas production
Number X volume per unit = volume per day Number X volume per unit = gas per day

Example: 2 buffalo X 15 kg/day = 30 kg/day 2 x 0.540 m³/day = 1. 08 m³/day

Buffalo	X 15 kg/day	=	kg/day X 0.540 m³/day =	m³/day
Cows	X 10 kg/day	=	kg/day X 0.360 m³/day =	m³/day
Calves	X 5 kg/day	=	kg/day X 0.200 m³/day =	m³/day
Pigs (50 kg)	X 2 kg/day	=	kg/day X 0.180 m³/day =	m³/day
Horses	X 10 kg/day	=	kg|day X 0.350 m³/day =	m³/day
Sheep	X 2 kg/day	=	kg/day X 0.100 m³/day =	m³/day
Chickens	X 0.18 kg/day	=	kg/day X 0.011 m³/day =	m³/day
Toilets	X 0.4 kg/day	=	kg/day X 0.030 m³/day =	m³/day
Green material	kg/day X 0.200 m³/day =	m³/day

Gas and manure production per day kg/day m³/day
Does this correspond with livestock
in 5 years?
Increased
level X kg/day = kg/day m³/day = m³/day

Gas and manure production
potential kg/day m³/day:

Step 3: Comparison between gas volume needed and gas generation potential

Does potential gas production match requirements?	If so, the chosen size of plant is correct, and the next step can begin.
Is production greater than required?	It may be a good idea to build this plant nonetheless and to ask a neighbor if he alsorequires biogas; if not, build a smaller plant.
Is consumption higher than potential gas production? Check the following possible measures:	- Can consumption be lowered (calculate gas requirements again)?
	- Can more organic material be acquired as fuel (calculate gas production again)?
	- Can a plant be constructed jointly with a neighbor?

Step 4: Calculating influencing factors on the biogas plant

Temperature - fermentation period in digester

The fermentation time is an important factor in determining the size of the biogas plant and epends on the temperature in the digester. The fermentation period is defined as the time taken for material to flow through the plant from input to output. The following guide values apply to the regions stated:

30 - 40 days	Hot, tropical plains climate: e. g. Sudan, Cameroon, Sri Lanka, Indonesia, Venezuela,Central America
40 - 60 days	Hot regions which cool down only slightly in winter: e. g. India, Thailand, Philippines, Kenya, Ethiopia60 - 90 days More temperate climate with distinct drop in temperature during winter: e. g. China,Korea, Turkey

The table below shows the relationship between material fermentation time, temperature and gas output.

In regions with a distinct winter season or severe differences between daytime and nighttime, temperatures (mountainous regions) assume a temperature 5 °C lower for calculation purposes.

Digester pit temperature ºC

Fermentation period days

Quantity of material added

The material must be added in the form of a free-flowing liquid, or else blockages will occur, However, if it is diluted too much, gas production will be reduced.

Generally speaking, the solid material must be mixed with at least the same volume of water.

An accurate calculation depends on the analysis of the material and should be based on the list shown below.

Typical mixing ratios

Cow dung, fresh: water	1:0.5
Cow dung, superficially dry: water	1:1
Horse and sheep's dung: water	1:1
Green refuse: water	1:0.5 to 1:2

Quantity of material added per day:

Type of manure/material	Quantity (kg = 1)	Water (kg = 1)	Liters
Cow dung	+	=
Pig dung	+	=
Other animal faeces	+	=
Human excrete from toilets	+	=
Agricultural refuse	+	=

Volume added per day

liters

note: in case of concrete stable floor the collected urine is sufficient for dilation, no water needs to be added

Step 5: Establishing the dimensions of the biogas plant

Establishing the dimensions of the biogas plant
The volume of the digester pit is determined from the volume of material added per day multiplied by the
fermentation time.
Volume of material added per day X fermentation time =

	kg/day X	days =
	(1000 l = 1 m³)
Gas volume from plant per day:	m³/day
Size of gas holder = approx. 1/2 of daily gas production =	m³

About

With the steady increase in demand for the useful exploitation of renewable energy resources the transformation of biogas into shaft - or electrical power appears as one of the sensible options for biogas utilization.

This book wants to provide a source of information not only for the various technical aspects of modification of internal combustion engines, both Diesel- and Gasoline (Otto-)engines, to operate on biogas-fuel but also for planning and economic operation of these engines in a system comprising of the fuel generating biogas plant and the power consuming driven equipment.

The reader, who is assumed to have basic technical interest and understanding, will furthermore find information on the use of the engine's waste heat and a commented list of manufacturers of biogas engines and available equipment for the self-modification of engines.

Deutsches Zentrum für Entwicklungstechnologien
ISBN 3-528-02032-6