I have posted this before that eating meat increasing carbon emissions. Everybody in this planet, all living things produces methane and since is considered as a greenhouse gas so basically our burps, farts, and breath causes some form of carbon emission. These things cannot be avoided, its natural but why should we stop eating meat.
It comes down to efficiency. Cows and Sheep require 8kg of grain to produce 1 kg of meat and pigs 4kg per kg of meat. The most economical is chicken which uses 1.6kg of feed to produce 1kg of chicken. To know more visit the source.