The correct option is (c).
Explanation
Biogas is a renewable biofuel produced through the biological breakdown of organic matter in an oxygen-free environment. It is primarily composed of methane ($CH_4$) and carbon dioxide ($CO_2$) and serves as a clean energy source.
Statement-wise Analysis:
- Statement 1 is Correct: Biogas is produced from the decomposition of various organic substrates, including sewage sludge, animal manure (such as cow dung), agricultural residues, and municipal solid waste. The organic content in sludge serves as a nutrient-rich feedstock for the process.
- Statement 2 is Incorrect: Biogas production is a waste-to-energy process. It produces energy in the form of combustible methane gas, rather than consuming energy as a primary function. While the operational plant may utilize a small amount of power, the net outcome is energy generation.
- Statement 3 is Correct: The process is driven by anaerobic digestion. It involves the breakdown of biodegradable material by microorganisms, specifically anaerobic bacteria (methanogens), in the absence of oxygen.
Key Takeaway:
Biogas is a methane-rich fuel generated by the anaerobic decomposition of organic waste (sludge, biomass) by bacteria, functioning as a sustainable waste-to-energy solution.