How much methane does a cow emit each day?

Methane forms naturally during a cow’s digestion, but the amount is not the same for every animal. Studies of dairy cows have measured averages ranging from about 300 to nearly 600 liters per day depending on herd, diet, and method; the University of Nebraska gives about 500 liters as a reference for a dairy cow. So 400 liters is a plausible rough figure, but not a precise norm for an “average cow.” Methane is produced mainly by microbes in the rumen and is released mostly through belching.