Food waste in the U.S. is a big problem, accounting for about 31 percent of the nation’s food supply, or 133 billion pounds. It makes up 21 percent of U.S. municipal solid waste in landfills, and as a result it accounts for the lion’s share of landfill methane emissions. Methane is a greenhouse gas with a warming potential 21 times that of carbon dioxide — and landfills are the third largest source of methane emissions in the U.S.