Identify the correct option from the following about the proportion of different gases in Biogas ?
- A.Methane > Carbon dioxide > Nitrogen
- B.Methane > Nitrogen > Carbon dioxide
- C.Methane > Oxygen > Carbon monoxide
- D.Nitrogen > Methane > Carbon dioxide
Correct answer
Explanation
The correct answer is A, Methane > Carbon dioxide > Nitrogen. Biogas is mostly methane, with carbon dioxide as the second gas and only small amounts of nitrogen and others.
Biogas forms when cattle dung, kitchen waste or crop residue is broken down by anaerobic bacteria, that is, without air, inside a digester. A typical sample is about 50 to 75 per cent methane and 25 to 50 per cent carbon dioxide, with a few per cent of nitrogen and traces of hydrogen, hydrogen sulphide and moisture. Methane is the combustible part, so the more methane, the better the fuel. The slurry left behind is a nutrient-rich manure, which makes a gobar gas plant doubly useful in villages.
Option B is wrong because nitrogen is only a minor part and is far less than carbon dioxide. Option C is wrong because the digestion happens without air, so oxygen is almost absent and carbon monoxide is not a component. Option D is wrong because methane, not nitrogen, is the main gas.
Exam tip: biogas ≈ methane 50–75% + CO2 25–50%, made by anaerobic digestion.
Practice Questions
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Show answer
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