(AP) — For cattle fattened in fields instead of feedlots, the grass may be greener, but the carbon emissions are not.

A study out Monday in the Proceedings of the National Academy of Sciences finds that even in the most optimistic scenarios, grass-fed beef produces no less planet-warming carbon emissions than industrial beef. The finding calls into question the frequent promotion of grass-fed beef as a more environmentally friendly option. Still, other scientists say grass-fed beef wins out on other factors like animal welfare or local environmental pollution, complicating the choice for conscientious consumers.

“I think that there is a large portion of the population who really do wish their purchasing decisions will reflect their values,” said Gidon Eshel, a research professor of environmental physics at Bard College and one of the study’s authors. “But they are being misled, essentially, by the wrong information.”

When it comes to food, beef contributes by far the most emissions fueling climate change and is one of the most resource- and land-intensive to produce. Yet demand for beef around the world is only expected to grow. And carefully weighing the benefits of grass-fed beef matters because in most parts of the world where beef production is expanding, such as South America, it’s being done by deforesting land that would otherwise store carbon, said Richard Waite of the World Resources Institute.

Experts say this study’s finding makes sense because it’s less efficient to produce grass-fed cattle than their industrial counterparts. Animals that are fattened up in fields instead of feedlots grow more slowly and don’t get as big, so it takes more of them to produce the same amount of meat.

The researchers used a numerical model of the emissions produced across the process of raising beef, then simulated many herds of industrial and grass-fed cattle. It compared differences in how much food they would eat, how much methane and carbon dioxide they would emit and how much meat they would produce.