Which greenhouse gas is commonly produced by cattle?

Methane is the greenhouse gas commonly produced by cattle. It forms during enteric fermentation, the microbial digestion of plant material inside a cow’s rumen, one chamber of its complex stomach.

Cattle eat grasses and other cellulose-rich plants that the animals cannot break down unaided. Communities of microorganisms ferment this material and convert it into nutrients the cattle can use. Methanogenic archaea consume some of the resulting compounds and produce methane as a by-product. Most of that methane leaves the animal through belching, not primarily through flatulence.

Methane is a powerful greenhouse gas, although cattle emit much less of it by mass than humans emit carbon dioxide. Over a 20-year period, methane has a far greater warming effect per tonne than carbon dioxide, but it remains in the atmosphere for roughly a decade on average, while some effects of carbon dioxide persist for centuries or longer. Cattle can also generate methane when manure decomposes without oxygen.

Another common confusion is nitrous oxide, which is associated especially with fertilized agricultural soils and manure management. For the distinctive digestive emissions of cattle and other ruminants, however, methane is the canonical answer.