Belching Cows

When cows and other ruminants digest their food, methane builds up in their rumen, the largest chamber of their four-chambered stomach. Releasing that greenhouse gas -- mostly by belching -- accounts for 20 percent of all methane emissions in the United States, according to the Environmental Protection Agency.
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That's a problem, because methane is a far more powerful contributor to climate change than, say, carbon dioxide, since it prevents more heat and radiation from escaping into space.