And much of it is expected to be released in the form of methane, which is 20 times more potent a greenhouse gas than carbon dioxide. (cato-unbound.org)
So the first line of this article states methane and carbon dioxide are the two most potent greenhouse gases, but of the four major contributors, they're the least influential. (news.mit.edu)
He also found that some of those animals, cows in particular, emit a great deal of methane which is a very potent greenhouse gas emission. (michiganradio.org)