The rumen underpins much of our agricultural industry. Without this stomach chamber, cows and other ruminants would be much less efficient at turning grass into milk, meat and wool. A cow's rumen has a capacity of up to 95 litres and contains billions of bacteria and other microbes. These microbes produce the enzymes that digest cellulose into sugars and fatty acids for their hosts to use. A less desirable by-product is the potent greenhouse gas, methane: a single cow can produce up to 280 litres of methane a day.
The rumen is one of four stomach compartments found in ruminants. Ruminants are animals such as cattle, sheep, goats and deer. (In comparison, animals such as pigs, dogs and horses have only a single stomach compartment and are called nonruminants, or monogastric animals.) The rumen allows grazing animals to digest cellulose, a very common carbohydrate in plants. .