Final answer:
Anaerobic archaeans known as methanogens consume hydrogen and release methane gas as a byproduct during anaerobic respiration.
Step-by-step explanation:
Anaerobic archaeans that live in hydrogen-rich environments are known as methanogens. These organisms feed on hydrogen and, in the absence of oxygen, participate in anaerobic respiration. Methanogens are capable of reducing carbon dioxide to methane in this process, thereby oxidizing NADH to regenerate NAD+. As a byproduct of consuming hydrogen and reducing carbon dioxide, these archaeans release methane gas.
Methanogens are found in a variety of environments, including soil and the digestive tracts of ruminants such as cows and sheep. Their metabolic processes are significant for the carbon cycle and have implications for environmental concerns, because methane is a potent greenhouse gas. Additionally, methanogens represent a crucial step in the biological production and consumption of methane, a dynamic process that both contributes to and helps regulate methane levels in the atmosphere.