Grass-fed cows gain weight more slowly, so they produce more methane per unit of meat produced. However, it can be argued that grass fed cattle farming is a net positive for Greenhouse emissions, since the carbon captured by the larger pastures can offset the effect of the methane emissions from the cattle. In some cases the entire farm's operational emmisions could be offset. Note that this is climate dependent. [1]

It is important also to note that if the land were instead used for growing crop for human consumption, then the carbon capture effect would be far higher, and that generally grass fed beef in the US are fed grain in the final months before slaughter. Other factors like water usage of cattle farming per calorie produced compared to human consumed crop can put even grass fed cattle farming in a bad light.

[1]: https://www.npr.org/sections/thesalt/2019/08/13/746576239/is...

There's a large amount of range land which is impractical for farming. However, it is suited for grazing. It was used for bison before domestic cattle.

If we conclude that bovine grazing is harmful, should we conclude that exterminating the American bison was green?

Cattle/livestock is also used for improving the quality/fertility of the soil for growing crops. It drastically reduces the need for harmful fertlizers, the need to till the land as much (reducing diesel usage) etc.. Also, the milk and meat is a nice bonus.

The Sacred Cow documentary is worth watching which goes into detail of this cycle - including that a lot (most?) crops use animal manure for fertilizing, so you still need the animals.

Apart from that, livestock grazing has been used effectively to fight desertification by Allan Savory and others.

https://ourworld.unu.edu/en/reversing-desertification-with-l...

The article's point was that cows are a major source of greenhouse gases. Eating grass fed beef doesn't change that.

There's an effort to start to mass produce a type of algae that by adding a small % of it to their diet reduces methane by 80%+ from what I remember.