Roody, I thought methane is a better greenhouse gas than carbon dioxide. I mean it traps more heat so has a stronger effect. So, if the plant gets burned we get carbon dioxide but as cow farts its worse until the methane decomposes to carbon dioxide. Isn't that why the permafrost melting is such a concern?
Last year I splurged on some buffalo meat, totally grass fed and raised within a few hundred miles. It was expensive but very tasty. I followed the farmer's directions. I used to work with a hunter who would give away extra meat. Again, this non- grain fed meat was very tasty. I wonder if grass fed beef would use less land than grain fed? When I traveled around south asia it seemed that the towns there had a different system. The cows ate the garbage. Then the citizens collected the dung for fuel. The dried dung made an acrid smoke. It seems that the process could be improved by converting the dung to methane for fuel and using the remains for fertilizer for the fields making a more closed cycle and improving air quality. That was years ago, maybe today they have modernized and use landfills and factory farms and gotten the cows off the streets and made people purchase gas to cook with.
IIRC, methane is worse pound for pound, but that doesn't mean that methane from cow digestion is worse than CO2 from burning.
Good question if grass-feeding uses less land than grain-feeding. Certainly it abuses or misuses the land less! For me, another consideration is that grass-fed cattle lead a pretty normal life (for a cow) and presumably are "happier" than cattle crowded into dirty feedlots. Of course, the same goes for swine and poultry too.
The waste from meat production is an enormous problem. A large pig farm can house, IIRC, up to 30,000 hogs. That means there is as much waste as from a small city, and there are very few regulations for disposal of all that waste.
Compared to the myriad other issues, it seems like methane is the least of the worries related to meat production.