Biogas

Biogas is a combustible mixture of gases produced by micro-organisms when livestock manure and other biological wastes are allowed to ferment in the absence of air in closed containers. The major constituents are methane (CH4, 60 percent or more by volume) and carbon dioxide (CO2, about 35 percent); but small amounts of water vapour, hydrogen sulphide (H2S), carbon monoxide (CO), and nitrogen (N2) are also present.

The composition varies according to the biological material. The methane content produced from human waste, chicken manure and wastewater from slaughterhouse sometimes could reach 70 percent or more, while that from stalk and straw of crops is about 55 percent. This is mainly used as fuel, like natural gas, while the digested mixture of liquids and solids ‘bio-slurry’ and ‘bio-sludge’ are mainly used as organic fertiliser for crops.

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