A little seaweed with that? Cowirrie/Flickr, CC BY-SAMethane is a short-lived but powerful greenhouse gas and the second-largest contributor to climate change after carbon dioxide. And the majority of human-induced methane emissions comes from livestock. About 70% of agricultural methane comes from enteric fermentation – chemical reactions in the stomachs of cows and other grazing animals as they break down plants. The animals burp out most of this methane and pass the rest as flatulence. There