WHAT IS BIOGAS?

Biogas originates from bacteria in the process of bio-degradation of organic material under anaerobic (without air conditions. The natural generation of biogas is an important part of the biogeochemical carbon cycle. Methanogens (methane producing bacteria) are the last link in a chain of micro-organisms which degrade organic material and return the decomposition products to the environment. In this process biogas is generated, a source of renewable energy.

Biogas is a mixture of gases that is composed chiefly of:
· methane (CH4): 40-70 vol.%
· carbon dioxide (CO2): 30-60 vol.%
· other gases: 1-5 vol.%
including
· hydrogen (H2): 0-1 vol.%
· hydrogen sulfide (H2S): 0-3 vol.%

Like those of any pure gas, the characteristic properties of biogas are pressure and temperature dependent.

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.

The burning of biomass (manure, 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, pottasium 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 manure and other organic waste material, the resulting sludge is a very good fertilizer, supporting general soil quality as well as higher crop yields.