What gas is primarily produced in anaerobic digestion?

• A. Methane
• B. Oxygen
• C. Nitrogen
• D. Hydrogen sulfide

Answer: (A)

Anaerobic digestion produces biogas without oxygen, and the main gas in that biogas is methane. Specialized microbes called methanogens convert intermediates from the breakdown of organic matter into methane, making it the dominant component along with carbon dioxide. Oxygen isn’t produced in this process because there’s no oxygen present to begin with, and the system operates under anaerobic conditions. Nitrogen gas isn’t a primary product of digested material, though nitrogen can appear in other forms like ammonia. Hydrogen sulfide may form if sulfur compounds are present, but it’s usually a smaller portion and has a strong odor. So the gas most produced in anaerobic digestion is methane.