In comparison with other foods, beef has the highest carbon footprint by far — almost four times that of chicken and 10 to 100 times that of most plant-based foods, Our World in Data said.
Now, scientists have discovered that cows raised on grass-based diets their entire lives may have a carbon footprint that is higher overall than those that are switched to grain-based diets partway through, a press release from the Public Library of Science (PLOS) said.
Source: https://www.ecowatch.com/cow-farms-carbon-footprint-grass-grain.html