Which of the following two are the major constituent of Bio-gas?

Question

Which of the following two are the major constituent of Bio-gas?

1. Methane

2. Butane

3. Carbon dioxide

4. Carbon monoxide

Select the correct answer from the code given below:

1. A. 1 and 3 (Correct answer)
2. B. 3 and 4
3. C. 2 and 3
4. D. 1 and 2

Correct Answer

Option A — 1 and 3

Detailed Solution & Explanation

The correct answer is 1 and 3.

Key Points

• Biogas is produced by the anaerobic decomposition of organic matter, and its two major constituents are:
  • Methane (CH₄) — roughly 50-75%, the component that burns and gives the fuel value.
  • Carbon dioxide (CO₂) — roughly 25-50%.
• Butane is a constituent of LPG, not biogas, and carbon monoxide is a product of *incomplete* combustion, not a biogas constituent.
• Hence option (a).

Additional Information

• Biogas also contains small traces of hydrogen sulphide (H₂S), hydrogen, nitrogen and water vapour. H₂S is responsible for its characteristic smell and must be removed before use in engines.
• Gobar gas plants use cattle dung; the residue left behind is an excellent nitrogen- and phosphorus-rich manure, which is why biogas is treated as a doubly useful technology.
• Compare the fuel compositions frequently asked: LPG — butane and propane; CNG — mostly methane; Water gas — CO + H₂; Producer gas — CO + N₂.