. M ICROBES IN P RODUCTION OF B IOGAS Biogas is a mixture of gases (containing predominantly methane) produced by the microbial activity and which may be used as fuel. You have learnt that microbes produce different types of gaseous end-products during growth and metabolism. The type of the gas produced depends upon the microbes and the organic substrates they utilise.
In the examples cited in relation to fermentation of dough, cheese making and production of beverages, the main gas produced was CO . . However, certain bacteria, which grow anaerobically on cellulosic material, produce large amount of methane along with CO and H . These bacteria are collectively called methanogens , and one such common bacterium is Methanobacterium .
These bacteria are commonly found in the anaerobic sludge during sewage treatment. These bacteria are also present in the rumen (a part of stomach) of cattle. A lot of cellulosic material present in the food of cattle is also present in the rumen. In rumen, these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle.
Do you think we, human beings, are able to digest the celluose present in our foods? Thus, the excreta (dung) of cattle, commonly called gobar , is rich in these bacteria. Dung can be used for generation of biogas, commonly called gobar gas . The biogas plant consists of a concrete tank ( - feet deep) in which bio-wastes are collected and a slurry of dung is fed.
A floating cover is Figure . An aerial view of a sewage plant