Methane released by cows as a result of their digestive processes is a problem. It accounts for 25 percent of all methane emissions, and methane happens to be one of the worst greenhouse gases. Pound for pound, the comparative impact of methane on climate change is over 20 times greater than carbon dioxide over a 100-year period.
Source: Meet the cow-fart-backpack that wants to fight climate change – Big Think
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