Cattle digest their food through bacteria-aided fermentation, creating methane as a byproduct that’s exhaled by the animal. According to research by the UN Food and Agriculture Organization, the cattle industry accounts for about 20 percent of total human-associated methane emissions.
Interest in a greener steak may lead people to purchase grass-fed beef. According to Beef Magazine, the grass-fed beef sector has been experiencing a growth rate of 25-30 percent. But simulations of the cattle industry’s carbon footprint suggest transitioning to grass-fed beef won’t cut methane emissions.
"Finishing cattle on grass typically takes twice as long," said Dr. Jennifer Reeve, a professor of the Plants, Soils and Climate Department at Utah State University. "Obviously, they’re living twice as long, they’re producing twice as much methane, but also they’re producing more methane when they’re consuming a lower-quality diet."
She’s a member of a team of researchers at USU, who are trying to design pastures that are trying fatten cattle as quickly as grain can.
"We could reduce the methane emissions by cattle by improving their forage diet," Reeve said. "Legumes for example are a lot more nutritious than grasses. They’re also easier to digest because they have less cellulose. If you put cattle on alfalfa it’s very high quality forage, but if they’re consuming too much alfalfa at once they could bloat and suffocate. Tannin-containing forages aren’t bloat-causing and also increase the rate of gain. Preliminary data suggest that the rate of gain on these tannin-containing legumes approaches that of on grain."
Reeve believes these improved pastures could mitigate the greenhouse gas emissions of the beef industry. Until then, informed consumers must choose between a locally harmful low-emissions steak, a locally beneficial, high-emissions steak, or no steak at all.