Certain bacteria, which grow anaerobically on cellulosic material, produce large amount of methane along with.......... and.......... These bacteria are collectively called methanogens.

Step-by-step solution

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 CO2.. However, certain bacteria, which grow anaerobically