Cleaning up cow burps could combat global warming

In the urgent quest for a more sustainable global food system, livestock is a mixed blessing. On the one hand, by converting fibrous plants that people can’t eat into protein-rich meat and milk, grazing animals like cows and sheep are an important source of human food. And for many of the world’s poorest, raising a cow or two — or a few sheep or goats — can be a source of wealth. But those benefits come at an immense environmental cost. A 2013 study showed that globally, livestock are responsible for 14.5 percent of greenhouse gas emissions — more than all the world’s cars and trucks combined. And about 40 percent of livestock’s global warming potential comes in the form of methane, a potent greenhouse gas formed as they digest their fibrous diet. This dilemma is driving an intense research effort to reduce methane emissions from grazing animals. Existing methods, such as improved livestock practices and the recent development of feed additives, can help, but not at the scale ...