Scientists have long known that cattle produce carbon dioxide and methane throughout their lives, but a new study pinpoints the cow-calf stage as a major contributor of greenhouse gases during beef production. In a new paper for the Journal of Animal Science, scientists estimate greenhouse gas emissions from beef cattle during different stages of life. They show that, depending on which production system farmers used, beef production has a carbon footprint ranging from 10.7 to 22.6 kg of carbon dioxide equivalent per kg of hot carcass weight.