What is the main constituent of biogas? How is biogas obtained from biomass? Write any two advantages of using this gas.

The main component of biogas is methane, as it contains up to 75% methane gas. Other than methane, hydrogen, carbon dioxide and hydrogen sulphide are the gases present in biogas.

When biomass like cow-dung, vegetable waste, etc undergoes anaerobic degradation in the presence of water but in the absence of oxygen, then these complex substances are broken down into simpler substances and gases like methane, carbon dioxide, etc. Thus, biogas is obtained from biomass.

Two advantages of using biogas are as follows:

1. It is a clean fuel (smoke-free) with a high calorific value.

2. It utilises biowaste and sewage at a large scale for producing biogas.