1. CH₄ Emissions from Enteric Fermentation

Herbivore animals, ruminants (e.g., cattle, buffalo, sheep, goats, camels), and some non-ruminant animals (e.g., pigs, horses, asses, mules) produce CH₄ as a by-product of enteric fermentation.

Enteric fermentation is a digestive process by which carbohydrates are broken down by micro-organisms into simple molecules for absorption into the bloodstream.  Methane is produced during the process and may be released to the atmosphere.  The amount of methane produced and excreted by an individual animal is primarily dependent on the type of digestive system and the quantity and quality of feed consumed (which relates to the energy expenditure of the animal).  Ruminant animals have the highest emissions because of their specific digestive system and large micro-organism populations in the rumen.

Click on the factors of digestive systems and food intake on the Figure on the right to learn more about them.