The correct answer is B. Methane.
Biogas is a mixture of gases produced by the breakdown of organic matter in the absence of oxygen. The main components of biogas are methane (CH4), carbon dioxide (CO2), and hydrogen (H2). Methane is the most abundant component of biogas, typically accounting for 50-75% of the total volume. Carbon dioxide is the second most abundant component, typically accounting for 25-40% of the total volume. Hydrogen is the least abundant component, typically accounting for 0-10% of the total volume.
Biogas can be used as a renewable energy source to generate electricity, heat, and transportation fuel. It can also be used to improve soil fertility and reduce greenhouse gas emissions.
Option A: Carbon dioxide is the second most abundant component of biogas, typically accounting for 25-40% of the total volume. It is a greenhouse gas that contributes to climate change.
Option C: Hydrogen is the least abundant component of biogas, typically accounting for 0-10% of the total volume. It is a clean-burning fuel that does not produce greenhouse gases.
Option D: Hydrogen sulfide is a poisonous gas that is not found in biogas.