fossil fuels contribute 33% farm animals contribute 30%
Not astronomically; marginally. Anyone who's been around herbivore farm animals will tell you they fart. A lot.
Then again, farm plants are a further 18%.
A cow that's fed on gras and farts emits nothing that that gras didn't pick up and contributes virtually nothing to climate change in the long term.
Otherwise, I wonder if non fertilizer supported grass could support sufficient cows to satiate demand (which has not even peaked yet).
but focusing on that is shifting blame in an innefectual way of course. Pointing at cow farts puts the pressure on the individual and seeks to dampen effects in the short term. Pump up less or no fossil fuels with actual long term thinking and those fertilisers will automatically become more expensive. At that point tho our oversized animal herd becomes harder to support and beef becomes automatically a lot more expensive whilst at the same time the manure becomes more important.
Also, from that Wikipedia article:
There is accumulating research and data showing that oil and gas industry methane emissions – or from fossil fuel extraction, distribution and use – are much larger than thought.[35][36][37][38][39]
Still, my “astronomically dwarfs” looks to be overstating it by a wide margin.
Yeah, but they also provide 80% of the world's calories to animals' 20%
Apparently mainly rice growing. I knew paddy fields were bad, but I didn't know they were that bad. Per calorie I am sure it is more like a tenth that of ruminants, perhaps less, but still worth replacing with other carbohydrates.
Grass-fed beef cattle whose dung is "recycled" in a more natural way in the fields produce the same emissions as would wild ruminants such as antelope, bison, etc.
The biodiversity problem in the above refers mostly to new land clearances intended for farming, including for feedstock. This is minor in N. America and Europe, mostly as the clearances were done decades or over a century ago.
Table 3 in this source [0] shows enteric vs manure methane emissions are 158 vs 137 kg CH4/yr for dairy cows, who are mostly fed in feedlots, and 58 vs 2.4 for meat and other cattle, in the US and Canada. So the CH4 emissions range 65-fold from 2.4 to 158 depending on how the cattle are farmed.
[0] Revised methane emissions factors and spatially distributed annual carbon fluxes for global livestock. https://pmc.ncbi.nlm.nih.gov/articles/pmid/28959823/
Increasing herd sizes increases that equilibrium level and that is partially responsible for the overall increase.
But there are mitigations that can be applied there are feed additives that reduce the cow related methane emissions to 1%.
Overall point is cow farts can be a drop in the bucket in the overall scheme of things, all we have to do is modify their diet slightly. Should we do it yes. Is it a huge issue no.
Industrial methane leaks are a bigger problem, that methane when it breaks down will turn into co2 that was not there to begin with contributing to global warming permanently.
Cows produce around 50 kg CH4 per head per year. There's around 1.5 billion cattle. That's around 75 teragrams (million metric tons).
Humans release about 410 teragrams altogether. About 40 percent is agricultural. And another 40 percent is from fossils, namely natural gas.
The top 100 natural gas leaks release over 20 teragrams of methane a year. That's just the leaks. That's 400,000,000 cattle worth of methane just pissed into the wind.
Thanks!