The "Grass fed beef is carbon neutral because its circular" myth

#null

Some people argue that cows only emit the carbon that they consumed in grass, and the grass pulled that carbon out of the atmosphere, so therefore they have only released carbon that was already sucked up. Therefore a field of cows on grass is carbon neutral

However the main problem with this argument is that grass absorbs CO2 but cows emit methane. Grass pulls a kilo of carbon out of the atmosphere, and cows eat that and belch a kilo of carbon back out in the form of methane. You might think this is circular because a kilo was pulled out and then put back. But the fact that CO2 is pulled out and methane is put back is the problem.

Methane causes way more warming, 28-34 times more. But it degrades much faster. So we can think of methane as basically doing all it's warming now, whereas carbon does some warming now and more later. Even if the amount of warming is exactly the same, methane basically means that we get climate catastrophe now rather than in 100 years.

grass fed cows essentially convert CO2 in the atmosphere into methane, which is much more concentrated.

It's like this: Imagine that I throw a bucket of water at you. That sucks but it doesn't hurt. Now imagine instead I take the same amount of water and freeze it. I now throw a bucket sized block of ice at you. That would hurt! The amount of water is the same, but its been converted into something more dangerous.

If cows convert carbon from CO2 into methane perfectly efficiently, that means they convert 3.6636kg of CO2 into 1.3356kg of methane.

Also because methane is moving the atmosphere relatively quickly, reducing our beef intake will have quite rapid climate benefits.

People argue that beef is a small % of climate emissions, only a few percent. But The US' beef emissions (not including dairy) amounts to the entire emissions of Spain.

Methane breaks down quickly...into carbon dioxide. Though this is counted in the GWP

Minor issues

This assumes that your cows are literally only raised on the grass in your field and nothing else. Few cows are raised this way; even grass fed are often finished on grains.
Much of the carbon is held in the soil, not the grass. Unless you have tiny numbers of cows, your continuous grazing will gradually degrade the soil.

This misses the bigger picture

Even if they were net neutral, that is still bad, because it maintains current unsustainable levels of methane in the atmosphere. You're confusing "neutral" with "sustainable".
On the other hand, rewilding grasslands (most grassland in most countries used to be forest remember) sucks carbon out of the atmosphere.