Describe the contribution of microbes in the production of biogas.

(N/A) Microbes produce different types of gaseous end products during growth and metabolism.
- The type of gas produced depends upon the microbes and the organic substrates they utilize. In examples such as the fermentation of dough,cheese making,and the production of beverages,the main gas produced is $CO_{2}$.
- However,certain bacteria which grow anaerobically on cellulosic material produce large amounts of methane along with $CO_{2}$ and $H_{2}$. These bacteria are collectively called methanogens,and one such common bacterium is $Methanobacterium$.
- These bacteria are present in the rumen (a part of the stomach) of cattle.
- $A$ lot of cellulosic material present in the food of cattle is also present in the rumen. In the rumen,these bacteria help in the breakdown of cellulose and play an important role in the nutrition of cattle.
- Thus,the excreta (dung) of cattle,which is also called 'gobar',is rich in these bacteria. Dung can be used for the generation of biogas,commonly called 'gobar gas'.
- The biogas plant consists of a concrete tank ($10$-$15$ feet deep) in which bio-wastes are collected and a slurry of dung is fed. $A$ floating cover is placed over the slurry,which keeps on rising as the gas is produced in the tank due to microbial activity.
- The biogas plant has an outlet which is connected to a pipe to supply biogas to nearby houses.
- Biogas is a mixture of gases (containing predominantly methane) produced by microbial activity and can be used as fuel.