It kind of goes both ways, today's factory farmed meat is grown with lots of grains and corn which is grown using artificial fertilizer, that is a lot of waste.

It kind of goes both ways, today's factory farmed meat is grown with lots of grains and corn which is grown using artificial fertilizer, that is a lot of waste. But a bit more traditionally and on smaller scales you donn't feed cows much of any grains, that is for people to eat, they eat the alfalfa which is grown in rotation to put nutrients/fertilizer into the soil for free and without any pollution. So eating meat is both very polluting, but once was and still could be a net positive for agricultural sustainability and reducing fossil fuel pollution.