That’s why you harness your cows with an anal pilot light, to flare off methane and prevent it from reaching the upper atmosphere.

EDIT: More seriously, for cows kept in a barn, probably better to capture or flare it off at a roof vent:

https://www.bbc.com/news/world-europe-25922514

German cows cause methane blast in Rasdorf

Methane gas released by dairy cows has caused an explosion in a cow shed in Germany, police said.

The roof was damaged and one of the cows was injured in the blast in the central German town of Rasdorf.

Thanks to the belches and flatulence of the 90 dairy cows in the shed, high levels of the gas had built up.