bio

Methanogenesis

The process by which a group of archaea combine hydrogen with carbon dioxide to make methane, harvesting energy from the reaction. Its ecological role is far larger than it sounds: in every fermentation chamber on Earth, methanogens are the organisms that eat hydrogen the instant it is produced. That arrangement — interspecies hydrogen transfer — is not a leak in the system but the thing that makes the system work, since fermenters can only keep going while someone downstream keeps clearing the hydrogen away. It is also why a cow evolves cubic metres of hydrogen a day and exhales essentially none.