A cow has four stomachs: the rumen, reticulum, omasum and abomasum. The rumen is the largest stomach and acts as a fermentation chamber. The abomasum is last of the four and is comparable in both structure and function to the human stomach.
With all its grazing and many stomachs, it is no wonder that cows are one of the main contributors to the hole in the ozone layer. Apart from CFC, the biggest culprit is hydrocarbon emissions from cars and cows. Yes, cows! Cows release some 100 million tons of hydrocarbon annually - by releasing gas. To give you an idea of how much gas a cow emits: if the gas of 10 cows could be captured, it would provide heating for a small house for a year.
But unlike what you think, cows release hydrocarbon mostly by burping.