Correct Answer:
C. Methane.
Explanation:
The correct answer is Methane. because it is the primary combustible gas produced during the anaerobic breakdown of organic matter.
- Step 1 (Composition Analysis): Biogas is a renewable energy source primarily composed of Methane (CH₄), which typically makes up 50% to 75% of the total volume, alongside Carbon Dioxide (CO₂).
- Step 2 (Energy Source): Methane is the specific component that gives biogas its energy content, allowing it to be captured and burned for heating, electricity, or vehicle fuel.
- Incorrect Options:
- Propane is incorrect because it is a three-carbon alkane dominant in Liquefied Petroleum Gas (LPG), not biological biogas.
- Butane is incorrect because it is a four-carbon alkane used in lighter fluid and LPG, not generated in large quantities by anaerobic digestion.
- Ethane is incorrect because it is a minor trace component in fossil natural gas, but not a primary element of biogas.