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Don’t sacrifice your daily omelet quite yet. According to the World Resources Institute’s protein scorecard, eggs have a lower greenhouse gas emission toll than dairy products such as yogurt and cheese. Part of the reason, according to Peter Newton, PhD, assistant professor at University of Colorado’s Environmental Studies program, is cow flatulence—really! “Because they’re ruminants, cow digestive systems produce large amounts of methane, and the amount of space needed to graze cattle [and dairy] in particular is huge,” he says. Although there is much less methane than carbon dioxide in the atmosphere (research from 2015 shows methane accounted for 10 percent of greenhouse gases, while carbon dioxide accounted for 82 percent), methane is more potent and can trap about

25 times more heat than carbon. So from a carbon footprint perspective, eggs are green—just hold the ham.