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Benefits of biogas technology

Well-functioning biogas systems can yield a wide range of benefits for their users, the society and the environment in general (see illustrations):  

(a)                   Production of energy (heat, light, electricity)
The calorific value of biogas is about 6 kWh/m3 — this corresponds to about half a litre of diesel oil. The net calorific value depends on the efficiency of the burners or appliances. Methane is the valuable component under the aspect of using biogas as a fuel. Biogas use, replacing conventional fuels like kerosene or firewood, allows for the conservation of environment. It therefore, increases its own value by the value of i.e. forest saved or planted. Biogas is able to substitute almost the complete consumption of firewood in rural households.  
1 m3 Biogas (approximately 6 kWh/m3) is equivalent to:
  • Diesel, Kerosene (approx. 12 kWh/kg)          0.5 kg
  • Wood (approx. 4.5 kWh/kg)                              1.3 kg
  • Cow dung (approx. 5 kWh/kg dry matter)      1.2 kg
  • Plant residues (approx. 4.5 kWh/kg d.m.)     1.3 kg
  • Hard coal (approx. 8.5 kWh/kg)                        0.7 kg
  • City gas (approx. 5.3 kWh/m3)                          1.1 m3
  • Propane (approx. 25 kWh/m3)                           0.24 m3  

The biogas generated from small and medium sized units (up to 6m3) is generally used for cooking and lighting purposes. Large units and/or communal units produce this gas in large quantities and can be used to power engines and generators for mechanical work or power generation.

(b)                   Transformation of organic wastes into high quality organic fertilizers  
The biogas digester is fed with cow dung slurry or organic wastes at a design rate, which is governed by local parameters. The output from the digester (digested manure) is actually a high quality organic fertilizer.
  This fertilizer is very important, especially in a country where the farmers do not have the resources to buy chemical fertilizers frequently. It has been calculated through lab tests that the fertilizer which comes from a bio-gas plant contains three times more nitrogen than the best compost made through open air digestion. If you compost chicken manure, for example, the finished compost will have in it only 1.58 to 2%o nitrogen. The same manure digested in a bio-gas plant will analyze 6% nitrogen. This nitrogen is already present in the manure. The nitrogen is preserved when waste is digested in an enclosed biogas plant, whereas the same nitrogen evaporates away as ammonia during open air composting.   Bio-fertilizer is a 100 % natural and organic fertilizer, based on composted organic material (=> renewable energy source). The composting process is achieved through microbe activity and contains all the nutrients and microbe organisms required for the benefits of the plants. Bio-fertilizers also secrete growth promoting substances like hormones, vitamins, amino acids and anti-fungal chemicals, as well as improve seed germination and root growth. Bio-fertilizers, thereby also aid in the better establishment of plants.  

(c)                   Improvement of hygienic conditions through reduction of pathogens, worm eggs and flies
Qualitative information from various household surveys has revealed that problems like respiratory illness, eye infection, asthma and lung problems have decreased after installing a biogas plant.   If parasitic diseases had previously been common, the improvement in hygiene also has economic benefits (reduced working time). The more fully the sludge is digested, the more pathogens are killed. High temperatures and long retention times are more hygienic.   The following are the principal organisms killed in biogas plants:  
  • Typhoid  
  • Paratyphoid,  
  • Cholera and dysentery bacteria (in one or two weeks),  
  • Hookworm and bilharzia (in three weeks).  
  • Tapeworm and roundworm die completely when the fermented slurry is dried in the sun.
The availability of biogas can have effects on nutritional patterns too. With easy access to energy, the number of warm meals may increase. Whole grain and beans may be cooked longer, increasing their digestibility, especially for children. Water may be boiled more regularly, thus reducing waterborne diseases.  

(d)                   Reduction of workload, mainly for women, in firewood collection and cooking  
To gather wood, women can spend up to 2-4 hours per day searching and carrying the firewood.
Once a biogas unit is installed, women will more time to engage in other useful activities such as education and interesting activities outside the home.   Biogas plants also improve health conditions in the homes:  
  • Since biogas burns clean, homes do not fill with smoke and ash.  
  • Women and children experience less bronchial problems and can expect to live longer.  
  • Homes are also more hygienic.  
  • Dung cakes are no longer stored in the homes.  
  • Cooking with gas takes less time than with wood or charcoal or any other commonly used fuel.  
  • It is easier to cook with gas stove.   The annual time saving for firewood collection and cooking averages to almost 1000 hours in each household provided with a biogas plant.  
(e)                   Environmental advantages through protection of soil, water, air and woody vegetation  
Estimating an average per capita consumption of 3 kg of wood per day for energy (cooking, heating and boiling water) in rural areas, the daily per capita demand of energy equals about 13 kWh which could be covered by about 2 m3 of biogas. A biogas plant therefore directly saves forest.
  Annually, each biogas plant can save more than four ton's of firewood and 32 litres of kerosene.   A single biogas system with a volume of 100 cubic feet (2.8 m3) can save as much as 0.3 acres (0.12 ha) of forest (woodland) each year.   A recent study by Winrock, Nepal and others found that each biogas plant can mitigate about five tons of carbon dioxide equivalent per year.   The credits thus earned could provide alternative financing for the sustainability of biogas program in that particular region.   The widespread production and utilization of biogas is expected to make a substantial contribution to soil protection and amelioration. First, biogas could increasingly replace firewood as a source of energy. Second, biogas systems yield more and better fertilizer. As a result, more fodder becomes available for domestic animals. This, in turn, can lessen the danger of soil erosion attributable to overgrazing.  

(f)                    Micro-economical benefits through energy and fertilizer substitution, additional income sources and increasing yields of animal husbandry and agriculture
Biogas plants will provide following benefits and the micro-level:  
  • Savings for the owners who would otherwise have to purchase other forms of energy;  
  • Incomes from sale of organic manure/fertilizer;  
  • Increased involvement in income generation activities such as production of pastries, chips and other food items for sale in villages,  
  • Substitution of chemical fertilizers with the organic fertilizers from biogas plants;  
  • Job creation for local technicians  
Benefits of biogas energy
Products of biogas technology
Biogas production and product options
  • The potential beneficiaries of the standards include:
  • Public policy holders: International Standards in this important area will help to address a global problem of great interest to public policy holders.
  • Companies: International Standardization in this area will standardize biogas related to technologies thereby creating increasing accessibility to companies who produce and use biogas technologies.
  • Consumers: Improved and streamlined technology will improve access to consumers.
  • General public: As indicated above, there potential societal benefits include improved health, reduced pollution, increased employment and improved integration in the cultural and educational sectors. 
The costs of biogas technology
An obvious obstacle to the large-scale introduction of biogas technology is the fact that the poorer strata of rural populations often cannot afford the investment cost for a biogas plant. This is despite the fact that biogas systems have proven economically viable investments in many cases.
Efforts have to be made to reduce construction cost but also to develop credit and other financing systems. A larger number of biogas operators will ensure that, apart from the private user, the society as a whole can benefit from biogas. Financial support from the government can be seen as an investment to reduce future costs, incurred through the importation of petrol products and inorganic fertilizers, through increasing costs for health and hygiene and through natural resource degradation.

Fuel and fertilizer

In Kenya, there is a direct link between the problem of farm fertilization and progressive deforestation due to high demand for firewood. In many rural areas, most of the inhabitants are dependent on fuelwood, dung and organic residue as fuel for cooking and heating. The burning of dung and plant residue is a considerable waste of plant nutrients. Farmers in developing countries are in dire need of fertilizer for maintaining cropland productivity. Nonetheless, many small farmers continue to burn potentially valuable fertilizers, even though they cannot afford to buy chemical fertilizers. At the same time, the amount of technically available nitrogen, potassium and phosphorous in the form of organic materials is around eight times as high as the quantity of chemical fertilizers actually consumed in developing countries. Especially for small farmers, biogas technology is a suitable tool for making maximum use of scarce resources: After extraction of the energy content of dung and other organic waste material, the resulting sludge is still a good fertilizer, supporting general soil quality as well as higher crop yields.

Public and political awareness

Popularization of biogas technology has to go hand in hand with the actual construction of plants in the field. Without the public awareness of biogas technology, its benefits and pitfalls, there will be no sufficient basis to disseminate biogas technology at grassroots level. At the same time, awareness within the government is essential. Since impacts and aspects of biogas technology concern so many different governmental institutions (e.g. agriculture, environment, energy, economics), it is necessary to identify and include all responsible government departments in the dissemination and awareness-raising process.

Biogas resource documents

Downloadable reference documents

Basic texts
Biogas - what it is, how it is made, how to use it

Biogas – Green energy process, design, energy supply, environment

Biogas from AD - Training manual

Biogas from AD of biomass

Biogas methane explained & other articles

Biogas Digest Volume I - Biogas basics
Biogas – An introduction
A system approach to biogas technology
About dry fermentation in agriculture

Alternative energy sources - Biogas production

Anaerobic digestion-02
Biomethane from biomass, biowaste and biofuels
Dry fermentation – From biowaste to biogas

Biogas brochure

Microbiological handbook for biogas plants