A rapidly growing industry in China—dairy farming—is also a major new source of greenhouse-gas emissions. But Huishan Dairy in northeast China is trying to change this by installing the world’s largest system for generating electricity by collecting methane gas emitted by fermenting cow manure. The Chinese have not, historically, been big milk drinkers, but decreasing costs and aggressive marketing efforts have changed that. Huishan’s new system will prevent methane—which is 23 times more potent than carbon dioxide as a greenhouse gas—from reaching the atmosphere. It will also reduce waste and odors, and produce a valuable organic fertilizer that’s safer than raw manure.