Beef CO2 emissions is more than cows breathing. Theres a lot of fuel burned when moving them around, making feed for them etc. I can't quite remember, but for every 100 calories of food eaten by cows, you end up with 3 calories worth of beef.

So right there off the bat, beef CO2 / calorie is 30x higher than the plants they eat (or whatever the multiplier was).

We didn't do any of these for the bison.