Which is the chief constituent of biogas?

Appeared in: MNS 2015

Explanation

Biogas is a mixture of gases produced by the anaerobic (in the absence of oxygen) decomposition of organic matter.
Methane (CH₄) is the primary component of biogas, typically comprising 50-75% of the total volume.
Methane is the component that burns, which makes biogas a valuable renewable fuel source.
The other major component is carbon dioxide (CO₂), with only trace amounts of other gases.

Option A: Chlorine is a halogen gas used as a disinfectant, particularly for water treatment. It is not a product of anaerobic digestion and is not found in biogas.
Option C: Biogas production is strictly an anaerobic process, meaning it occurs in the complete absence of oxygen. Therefore, oxygen cannot be a constituent.
Option D: Hydrogen is produced as an intermediate product during anaerobic digestion, but it is then consumed by methanogenic bacteria to form methane. Consequently, it is only present in trace amounts (less than 1%) in the final biogas mixture, not as the chief constituent.

Clinical Relevance

Nursing practice connection: Knowing Composition of Biogas helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Biogas technology is a key component of public health engineering, particularly in rural and community settings for waste management and energy production.
Proper disposal of organic waste (like human excreta, animal manure, and agricultural residue) through biogas plants prevents soil and water contamination, reducing the incidence of enteric diseases.
The use of biogas for cooking reduces indoor air pollution compared to burning solid fuels like wood or coal, thus lowering the risk of respiratory illnesses.

How to Approach the Question

First, identify the core concepts in the question: 'biogas' and 'chief constituent'.
Recall the definition of biogas: a fuel gas produced from the anaerobic digestion of organic waste.
The term 'chief constituent' asks for the component present in the largest amount.
Analyze the options based on the process. Since it's anaerobic, 'Oxygen' can be eliminated immediately.
Consider the function of biogas as a fuel. The primary flammable component of natural and biogases is methane.
Eliminate 'Chlorine' as it's a disinfectant and not related to organic decomposition.

Concept Tested & Keywords

QDBmFmZAkUAxHtcgE-MScD

E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) pp. 78-80, 32-34

Practise the full MNS 2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.