Sources of fuel obtaining from organic material is call as biomass.
Cow-dung, various plant materials like the residue after harvesting the crops, vegetable waste and sewage are decomposed in the absence of oxygen to give bio-gas.
- The plant has a dome-like structure built with bricks.
- A slurry of cow-dung and water is made in the mixing tank from where it is fed into the digester.
- The digester is a sealed chamber in which there is no oxygen.
- Anaerobic micro-organisms that do not require oxygen decompose or break down complex compounds of the cow-dung slurry.
- It takes a few days for the decomposition process to be complete and generate gases like methane, carbon dioxide, hydrogen and hydrogen sulphide.
- The bio-gas is stored in the gas tank above the digester from which they are drawn through pipes for use.
- Bio-gas is an excellent fuel as it contains up to 75% methane.
- It burns without smoke, leaves no residue like ash in wood, charcoal and coal burning.
- Its heating capacity is high. Bio-gas is also used for lighting.
- The slurry left behind is removed periodically and used as excellent manure, rich in nitrogen and phosphorous.
- The large-scale utilisation of bio-waste and sewage material provides a safe and efficient method of waste-disposal besides supplying energy and manure.