So why do cows make methane?
THE potent greenhouse gas is produced by ruminant animals such as cows, sheep and goats, all of which have additional stomachs.
The bacteria in their digestive systems produce methane as they break down the food and then the animals belch most of it out through their mouths and nostrils.
Not much methane is formed in the hind gut and even less is passed as gas.
The average dairy cow in Ireland emits about 120kg of methane gas every year. Holstein-Friesian cows, weighing in at around 490kg, have been found to emit between 350 and 415 grams of methane gas a day.