Beef has such a massive carbon footprint that eating a lot of burgers can theoretically be worse for the environment than driving a car . But most of that impact comes from the food grown for cows–and what cows eat could soon change.

A new study shows that cattle might be able to start eating algae instead of their usual farmed grain. The algae meal, leftover when manufacturers use algae biofuel, is usually burned–but it turns out that cows think it’s tasty.

“After the oil extraction process, the algae residue includes some fat, fiber, and protein, all essential nutrients for cattle,” says Stephanie Hansen, an associate professor of “beef feedlot nutrition” at Iowa State University and one of the authors of the study. “Cattle are well suited to digesting fibrous feedstuffs like the algae meal, making it a great ruminant feedstuff.”

Cows eat enormous quantities of feed partly because they digest food so inefficiently. Beef normally takes 28 times more land to produce than pork or chicken. It also takes 11 times more water, and produces five times more climate emissions than other meat. And though cow belches and manure account for part of the pollution, most of the problem comes from the growing the grains cows eat and converting it into animal feed.

“The footprint of conventional beef is nearly entirely due to production of its feed,” says Gidon Eschel, who calculated the carbon footprint of different meats in a different study last year. “So feed is where it’s at.”

Algae, unlike something like corn, can be grown with very little energy, land, and water. The researchers are working with Solazyme, a company that uses sugar in fermentation tanks to grow algae for biofuel. “It’s a very low carbon process,” says Jill Kaufmann Johnson, the company’s head of sustainability. “The feedstock of sugar cane happens to be a very low impact carbon source, and it’s rain-fed. And waste sugar cane powers the entire production process.” The whole process also requires much less land than something like corn or pasture.

Cows probably can’t switch completely to eating algae, but it can replace a substantial portion of other crops. In the study, some of the cattle ate food that was almost half microalgae. “The algae meal would be best suited as a part of a complete diet for cattle, replacing a portion of the corn or other feedstuffs typically used in the diet,” Hansen says.