> methane decomposes to CO2 in atmosphere in a decade or two, which is then captured by grass
But methane is a worse greenhouse gas than CO2, so it's not neutral at all.
You're also assuming that cattle are fed naturally occurring grass rather than industrial livestock feed, which I don't have numbers for but I assume is not carbon-neutral.
But methane is a worse greenhouse gas than CO2, so it's not neutral at all.
It is worse, but it doesn’t matter: as long as cattle population stays at constant levels, so will the amount of methane in the atmosphere that resulted from cattle emissions. You only get climate change from growing amount of greenhouse gases.
> You're also assuming that cattle are fed naturally occurring grass rather than industrial livestock feed, which I don't have numbers for but I assume is not carbon-neutral
In fact, I’m not; I explicitly mention artificial fertilizer, for example, which is typically not used to produce hay. The point is that to assess the effect of cattle on warming, you should focus on fossil inputs into it, not on methane. I think is quite likely that methane production from gastric fermentation in North America these days is lower than, say, in 1500s, where 60 millions bisons alone roamed the plains, along with another tens of millions of deer and other ruminants.
But methane is a worse greenhouse gas than CO2, so it's not neutral at all.
You're also assuming that cattle are fed naturally occurring grass rather than industrial livestock feed, which I don't have numbers for but I assume is not carbon-neutral.