Biogas system at household level fed daily with cattle manure [Cambodia]

ប្រពន្ធ័ឡជីវៈឧស្ម័នប្រើសំរាប់គ្រួសារប្រចំាថៃ្ងដោយប្រើលាមកគោ (Khmer)

technologies_1645 - Cambodia

Completeness: 80%

1. General information

1.2 Contact details of resource persons and institutions involved in the assessment and documentation of the Technology

Key resource person(s)

SLM specialist:
SLM specialist:

Khun Lean Hak



SLM specialist:

Pith Khonhel



SLM specialist:

Bin Sreytouch



SLM specialist:

Say Mesa



Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Society for Community Development in Cambodia (SOFDEC) - Cambodia
Name of the institution(s) which facilitated the documentation/ evaluation of the Technology (if relevant)
Local Agricultural Research and Extension Centre (LAREC) - Cambodia

1.3 Conditions regarding the use of data documented through WOCAT

The compiler and key resource person(s) accept the conditions regarding the use of data documented through WOCAT:


1.4 Declaration on sustainability of the described Technology

Is the Technology described here problematic with regard to land degradation, so that it cannot be declared a sustainable land management technology?


2. Description of the SLM Technology

2.1 Short description of the Technology

Definition of the Technology:

Small-scale biogas systems fed with cow manure and water are implemented in order to supply the household with energy for cooking and lighting, as well as to produce fertilizer.

2.2 Detailed description of the Technology


In this case-study, a small-scale biogas system was introduced in order to generate both energy for home consumption and fertilizer. Small-scale biogas systems are implemented in different parts of the world, however the layout thereof varies considerably.
The model used in this case-study consists of different components (cf. technical drawing). First, there is an inlet where the land user puts cow manure mixed with water. On the bottom of the inlet, there is a board which closes the access to the bio-digester situated beneath the inlet. The board can be opened manually by pulling a string. Once the board is open, the fluid components go through a pipe which leads to the bio-digester. In the bio-digester, bacteria transform the organic matter into biogas (mainly methane and CO2) and slurry. At the other end of the digester, there is another pipe (outlet). The outlet is lower than the inlet, and due to the difference in pressure, the slurry is pushed out of the digester. The slurry is dried and applied to the fields two to three times a year with the help of an ox cart. It has similar effects on the plant growth as chemical fertilizer as it does not build up the soil organic matter as much as compost. The biogas, however, is pushed to the pipe situated on top of the digester and can be utilized for domestic uses. The gas is used for cooking and lighting.

The use of biogas allows reducing the expenses on charging batteries for the lighting, as well as reducing the firewood use (usually from deforestation) for cooking. The slurry reduces the expenses on chemical fertilizer in the fields and has the advantage of killing the weed and rice seeds present in the manure and crop residues.

For building the biogas system, there is governmental and NGO support. These two actors finance half of the construction costs. The other half is paid by the land user. Building a biogas system is quite costly, with about 400 $, and not all of the land users in the area can afford paying 50% of its price. However, the costs borne by the land user are paid off within a few years due to reduced expenses on firewood, chemical fertilizer, and charging batteries. The construction itself was undertaken by local companies.
The costs are paid off within a few years due to the reduced expenses on firewood, chemical fertilizer and battery charging.

The analysed area is flat (slope < 2%), tropic (dry and wet season), and the soils are mostly sandy or loamy. The soils contain little organic matter (low soil fertility, acidification, small amount of cattle, area has been deforested a long time ago) and the groundwater table is rather high (1-3 m during the dry season, on the surface during wet season).
Due to climate change, the rainfalls are more erratic, temperatures rise and droughts are more recurrent. Rice is the predominant crop grown in the area, since it serves as staple food (mix subsistence and commercial activities). Rice is often grown in monocultures and harvested once a year. Once the rice is harvested (dry season), the cattle are released to the paddy fields. The cattle is often replaced by hand tractors, which effects the production of manure but allows a higher amount of crop residues on the fields.
As an addition to rice, most land users grow vegetable and fruits in small home gardens (subsistence) and complement their income by producing handicrafts or through off farm income / remittances from family members working in other places. The increasing migration rate (the young generation leaves the villages to work in the cities, garment industry or abroad) results in a decrease of available labour force in the area which has detrimental effects on the agricultural activities. Furthermore, the civil war in the 1970s (Khmer Rouge) led to the loss of agricultural knowledge which different NGOs try to re-establish.

2.3 Photos of the Technology

2.5 Country/ region/ locations where the Technology has been applied and which are covered by this assessment



Region/ State/ Province:

Kampong Chhnang

Further specification of location:

Sre Ouk Samlor Sap/Taing Krasaing/Rolear Pha,er

Specify the spread of the Technology:
  • evenly spread over an area
If precise area is not known, indicate approximate area covered:
  • 0.1-1 km2

There are only 4 households in this village which apply the technology (lack of money and/or cattle). However, similar Technologies are introduced in other provinces – yet it is difficult to estimate the area covered. Estimation for this village.

2.6 Date of implementation

If precise year is not known, indicate approximate date:
  • less than 10 years ago (recently)

2.7 Introduction of the Technology

Specify how the Technology was introduced:
  • through projects/ external interventions
Comments (type of project, etc.):

LWS (a Dutch NGO) in joint efforts with specialists from the National Biodigester Program NBP. Implementation in 2012

3. Classification of the SLM Technology

3.1 Main purpose(s) of the Technology

  • improve production
  • create beneficial economic impact

3.2 Current land use type(s) where the Technology is applied



  • Annual cropping
Number of growing seasons per year:
  • 1

Longest growing period in days: 210, Longest growing period from month to month: June-December

Settlements, infrastructure

Settlements, infrastructure

  • Settlements, buildings
  • biogas system

Major land use problems (compiler’s opinion): Lack of organic matter, lack of water retention in soil, irregularity of rainfall, low soil fertility (sandy soil), monocultures, bare soil during dry season, ploughing.
Major land use problems (land users’ perception): Low soil fertility, lack of water.
Livestock is grazing on crop residues
Constraints of settlement / urban
Constraints of infrastructure network (roads, railways, pipe lines, power lines)

3.5 SLM group to which the Technology belongs

  • energy efficiency technologies

3.6 SLM measures comprising the Technology

structural measures

structural measures

  • S11: Others
management measures

management measures

  • M6: Waste management (recycling, re-use or reduce)

Main measures: management measures
Secondary measures: structural measures

3.7 Main types of land degradation addressed by the Technology

chemical soil deterioration

chemical soil deterioration

  • Cn: fertility decline and reduced organic matter content (not caused by erosion)
  • Ca: acidification
biological degradation

biological degradation

  • Bs: quality and species composition/ diversity decline

Main causes of degradation: soil management (Ploughing, soil is left bare for several weeks), crop management (annual, perennial, tree/shrub) (Rice monoculture (rice as staple crop)), change of seasonal rainfall (More erratic beginning of wet season), droughts (On dry soil, rice cannot be planted and if already planted, rice cannot grow), labour availability (High migration rates from the villages to garment industry, cities or abroad, influence agricultural activities (e.g. broadcasting instead of transplanting of rice seedlings)), education, access to knowledge and support services (Khmer Rouge regime in the 1970s, a lot of knowledge got lost)
Secondary causes of degradation: over-exploitation of vegetation for domestic use (Rice straw is removed for different domestic uses (cattle, mushroom cultivation, etc.)), overgrazing (Cattle eats rice straw left after harvest, less organic matter on the field, grazing is not managed), change in temperature (More hot days), Heavy / extreme rainfall (intensity/amounts), land tenure (Some incidents of land grabbing, land use rights not clear, corruption), poverty / wealth

3.8 Prevention, reduction, or restoration of land degradation

Specify the goal of the Technology with regard to land degradation:
  • prevent land degradation
  • reduce land degradation

4. Technical specifications, implementation activities, inputs, and costs

4.1 Technical drawing of the Technology

Technical specifications (related to technical drawing):

Biodigester. Inlet: top left; gas outlet: top centre; digestion chambre: centre; and outlet: right. For the comlete building instructions contact the NBP.
Technical knowledge required for field staff / advisors: high (The most challenging part is the construction of the construction of the Biodigester.)
Technical knowledge required for land users: low
Main technical functions: increase in nutrient availability (supply, recycling,…)
Secondary technical functions: increase in organic matter

Structural measure: Biodigester. Round shape. Tiles and concrete.
Width of ditches/pits/dams (m): 4 m^3
Structural measure: Connecting pipes made of plastic
Construction material (concrete): Tiles are covered in concrete.
Construction material (other): The most challenging part is the construction of the Biodigester.
Other type of management: Change of energy supply system for home consumption.


National Biodigester Programm,

4.2 General information regarding the calculation of inputs and costs

other/ national currency (specify):


If relevant, indicate exchange rate from USD to local currency (e.g. 1 USD = 79.9 Brazilian Real): 1 USD =:


Indicate average wage cost of hired labour per day:


4.3 Establishment activities

Activity Timing (season)
1. Construction of the biodigester by external experts. The land user did not help with the construction, he only paid 200 US$. The other 200 US$ were paid by the National Biodigester Program. Dry season, when water table is low.

4.4 Costs and inputs needed for establishment

Specify input Unit Quantity Costs per Unit Total costs per input % of costs borne by land users
Construction material Construction of biodigester 1.0 400.0 400.0 50.0
Total costs for establishment of the Technology 400.0
Total costs for establishment of the Technology in USD 0.1

4.5 Maintenance/ recurrent activities

Activity Timing/ frequency
1. Add manure and water to the inlet once per day all year round
2. Collect residuals from biodigester, spread it out and let it dry, and finally put it on the field. 3 times/year

4.6 Costs and inputs needed for maintenance/ recurrent activities (per year)

Specify input Unit Quantity Costs per Unit Total costs per input % of costs borne by land users
Labour Labour 1.0 121.5 121.5 100.0
Total costs for maintenance of the Technology 121.5
Total costs for maintenance of the Technology in USD 0.03

Machinery/ tools: Cart to bring residues from the biodigester onto the fields.

The costs were calculated for 1 biodigester with a capacity of 4 m3.

4.7 Most important factors affecting the costs

Describe the most determinate factors affecting the costs:

The most costly part of this Technology is the construction of the biodigester. Once the system is installed, the costs borne by the land user are low. Also, the land user can save money since he doesn’t need to buy firewood any more.

5. Natural and human environment

5.1 Climate

Annual rainfall
  • < 250 mm
  • 251-500 mm
  • 501-750 mm
  • 751-1,000 mm
  • 1,001-1,500 mm
  • 1,501-2,000 mm
  • 2,001-3,000 mm
  • 3,001-4,000 mm
  • > 4,000 mm
Specifications/ comments on rainfall:

1486.45 mm 2013 in Kampong Chhnang

Agro-climatic zone
  • sub-humid

27° to 35°C, 1486.45 mm 2013 in Kampong Chhnang

5.2 Topography

Slopes on average:
  • flat (0-2%)
  • gentle (3-5%)
  • moderate (6-10%)
  • rolling (11-15%)
  • hilly (16-30%)
  • steep (31-60%)
  • very steep (>60%)
  • plateau/plains
  • ridges
  • mountain slopes
  • hill slopes
  • footslopes
  • valley floors
Altitudinal zone:
  • 0-100 m a.s.l.
  • 101-500 m a.s.l.
  • 501-1,000 m a.s.l.
  • 1,001-1,500 m a.s.l.
  • 1,501-2,000 m a.s.l.
  • 2,001-2,500 m a.s.l.
  • 2,501-3,000 m a.s.l.
  • 3,001-4,000 m a.s.l.
  • > 4,000 m a.s.l.

5.3 Soils

Soil depth on average:
  • very shallow (0-20 cm)
  • shallow (21-50 cm)
  • moderately deep (51-80 cm)
  • deep (81-120 cm)
  • very deep (> 120 cm)
Soil texture (topsoil):
  • coarse/ light (sandy)
  • medium (loamy, silty)
Topsoil organic matter:
  • medium (1-3%)
  • low (<1%)

5.4 Water availability and quality

Ground water table:

< 5 m

Availability of surface water:

poor/ none

Water quality (untreated):

poor drinking water (treatment required)

Comments and further specifications on water quality and quantity:

Ground water tabel and availability of surface water data during dry seasons. People use water for drinking after filtering or boiling.

5.5 Biodiversity

Species diversity:
  • low
Comments and further specifications on biodiversity:

Only degraded forests are in the area.

5.6 Characteristics of land users applying the Technology

Sedentary or nomadic:
  • Semi-nomadic
Market orientation of production system:
  • mixed (subsistence/ commercial)
Off-farm income:
  • 10-50% of all income
Relative level of wealth:
  • rich
Individuals or groups:
  • individual/ household
  • women
  • men
Indicate other relevant characteristics of the land users:

Land users applying the Technology are mainly Leaders / privileged
Population density: 10-50 persons/km2
Annual population growth: 0.5% - 1%
Off-farm income specification: Handicraft, remittances and factory work.

5.7 Average area of land used by land users applying the Technology

  • < 0.5 ha
  • 0.5-1 ha
  • 1-2 ha
  • 2-5 ha
  • 5-15 ha
  • 15-50 ha
  • 50-100 ha
  • 100-500 ha
  • 500-1,000 ha
  • 1,000-10,000 ha
  • > 10,000 ha
Is this considered small-, medium- or large-scale (referring to local context)?
  • medium-scale

5.8 Land ownership, land use rights, and water use rights

Land ownership:
  • communal/ village
  • individual, not titled
Land use rights:
  • communal (organized)
  • individual
Water use rights:
  • open access (unorganized)

Land ownership is very complex. Most of the land belongs officially to the government, yet many land users hold a paper confirming they applied for a land title – but de iure, this paper is worthless.

5.9 Access to services and infrastructure

  • poor
  • moderate
  • good
  • poor
  • moderate
  • good
technical assistance:
  • poor
  • moderate
  • good
employment (e.g. off-farm):
  • poor
  • moderate
  • good
  • poor
  • moderate
  • good
  • poor
  • moderate
  • good
roads and transport:
  • poor
  • moderate
  • good
drinking water and sanitation:
  • poor
  • moderate
  • good
financial services:
  • poor
  • moderate
  • good

6. Impacts and concluding statements

6.1 On-site impacts the Technology has shown

Socio-economic impacts


crop production

Comments/ specify:

Dried residues are put in the garden (cucumber, pumpkin, watermelon) which increases nutrient availability.

energy generation

Income and costs

expenses on agricultural inputs

Comments/ specify:

He saves 50 $ on chemical fertilizer per year.

Socio-cultural impacts

health situation

Comments/ specify:

No smoke from open fire.

Contribution to human well-being

Comments/ specify:

On the long term livelihood is improved, because he saves over 60 $ per year in firewood and battery charging for light, as well as 50 $ for chemical fertilizer.

Ecological impacts

Water cycle/ runoff

water quality

Comments/ specify:

Pollution of groundwater due to washing out of nutrients.


soil organic matter/ below ground C

Comments/ specify:

Most of the carbon is transformed into methane, not available as organic matter.

Other ecological impacts

reduced weed seeds

Comments/ specify:

Compost usually not completely decomposed, as well as raw manure, contain lots of weed seeds.

energy generation (eg hydro, bio)

Comments/ specify:

Before the installation of the biogas system, the land user bought firewood.

deforestation for firewood


6.2 Off-site impacts the Technology has shown

groundwater/ river pollution

Comments/ specify:

Sludge is left to dry outside, nutrients washed out into groundwater. Not measurable.

6.3 Exposure and sensitivity of the Technology to gradual climate change and climate-related extremes/ disasters (as perceived by land users)

Gradual climate change

Gradual climate change
Season increase or decrease How does the Technology cope with it?
annual temperature increase well

Climate-related extremes (disasters)

Meteorological disasters
How does the Technology cope with it?
local rainstorm well
local windstorm well
Climatological disasters
How does the Technology cope with it?
drought well
Hydrological disasters
How does the Technology cope with it?
general (river) flood not well

Other climate-related consequences

Other climate-related consequences
How does the Technology cope with it?
reduced growing period well

6.4 Cost-benefit analysis

How do the benefits compare with the establishment costs (from land users’ perspective)?
Short-term returns:


Long-term returns:

very positive

How do the benefits compare with the maintenance/ recurrent costs (from land users' perspective)?
Short-term returns:

very positive

Long-term returns:

very positive

6.5 Adoption of the Technology

  • > 50%
If available, quantify (no. of households and/ or area covered):

100% or 4 land user families


100% of land user families have adopted the Technology with external material support
4 land user families have adopted the Technology with external material support
The farmers can ask the National Biodigester Program for subsidies, but need to pay half of it on their own. As the farmers often lack money and need at least 3 - 4 heads of cattle to produce enough manure while they switch more and more to hand tractors, not many farmers are building new biogas digesters.

6.7 Strengths/ advantages/ opportunities of the Technology

Strengths/ advantages/ opportunities in the land user’s view
Fertilizer production (sludge).
Saves money and time on the cooking fuel (previously wood) and electricity (charging batteries) for the light.
No weed seeds in the sludge compared to compost and raw manure if used as fertilizer.
Strengths/ advantages/ opportunities in the compiler’s or other key resource person’s view
Less deforestation for firewood.

6.8 Weaknesses/ disadvantages/ risks of the Technology and ways of overcoming them

Weaknesses/ disadvantages/ risks in the land user’s view How can they be overcome?
The residue does not improve the soil as much as compost. Make compost in addition to biogas to enhance the soil organic matter.
The building costs are prohibitive Increase subsidies from state or NGOs.
At least 3-4 heads of cattle or 4-5 pigs have to be kept to produce enough manure. Diversify production with different animals.
Work has to be done each day to produce biogas.
Weaknesses/ disadvantages/ risks in the compiler’s or other key resource person’s view How can they be overcome?
Overgrazing could become a problem as more cattle needs to be kept. Add slurry as a liquid fertilizer
Part of nitrogen is volatilized during the drying of the sludge.

7. References and links

7.1 Methods/ sources of information

  • field visits, field surveys
  • interviews with land users
When were the data compiled (in the field)?


7.2 References to available publications

Title, author, year, ISBN:

NBP National Biodigester Program

Available from where? Costs?

Title, author, year, ISBN:

Lam et al. 2009. Domestic Biogas Compact Course. University of Oldenburg.

Available from where? Costs?

Title, author, year, ISBN:

Gurung. 2009. Review of Literature on Effects of Slurry Use on Crop production. The Biogas Support Program

Links and modules

Expand all Collapse all