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Given the large live-stock population in India, we can use this fuel as a steady source. These fuels are obtained from plant and animal produces, so it is called bio-mass.
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
Animal dung in the form of dried cakes is also burned for domestic purposes. Animal dung contains vital nutrients. If burnt directly they produce a lot of smoke leading to air pollution. Instead animal dung can be converted into biogas which is a clean fuel. The residue which is rich in nutrients can then be used as manure.
The figure shows how a woman is cooking, using gas piped from community biogas plant. Animal and plant wastes are easily degraded by anaerobic micro-organisms in the presence of water. In this process gases such as methane, carbon dioxide, hydrogen and hydrogen sulphide are produced. This mixture of gases is called biogas. It contains about 65% methane, which is an excellent fuel. Biogas can be used in gas stoves as fuel, for street lighting, and also for running engines.
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