Explanation
The correct answer is A: Methanogens.
Biogas is a renewable energy source that is produced by the anaerobic digestion of organic materials, such as agricultural waste, food waste, and sewage. In a biogas plant, a mixture of organic materials is placed in an anaerobic digester, where it is broken down by a community of microorganisms, including bacteria and archaea.
Methanogens are a group of archaea that play a critical role in the anaerobic digestion process by producing methane gas as a metabolic byproduct. These microorganisms are responsible for the final stage of biogas production, where they convert the intermediate products of anaerobic digestion (such as organic acids and alcohols) into methane and carbon dioxide.
Nitrifying bacteria are involved in the nitrogen cycle and convert ammonia to nitrite and then to nitrate. Ammonifying bacteria break down nitrogen-containing organic compounds into ammonia. Denitrifying bacteria convert nitrate back into atmospheric nitrogen gas. While these bacteria are important in other environmental processes, they are not typically involved in the production of biogas.
