Identify the incorrect component of biogas.

The correct answer is Option (1) → Oxygen

Biogas is a mixture of gases, mostly methane, made by microbes. The microbes work in the absence of air, so oxygen is not one of its gases. Methanogens, such as Methanobacterium, produce the methane.

(1) Oxygen — Not a component of biogas. The digestion takes place without oxygen (anaerobically).

(2) Methane — A component of biogas. It is the main gas, and it is the fuel.

(3) Carbon dioxide — A component of biogas. It is produced along with methane.

(4) Hydrogen sulfide — A component of biogas. It is produced by the anaerobic bacteria in the sludge digesters.

NCERT Extract:
Microbes in Sewage Treatment – “… The remaining major part of the sludge is pumped into large tanks called anaerobic sludge digesters. Here, other kinds of bacteria, which grow anaerobically, digest the bacteria and the fungi in the sludge. During this digestion, bacteria produce a mixture of gases such as methane, hydrogen sulphide and carbon dioxide. These gases form biogas and can be used as source of energy as it is inflammable.”