The additional problem with Methane (CH4) is that it has something like a ten year life span, in the atmosphere. Although it eventually decreases by reaction we are probably releasing more than enough to compensate. Although deep mining (coal) releases much of the Methane, open surface mining (metals) does too, to a lesser extent. (Building homes, large business structures is a 'double whammy'. Not only releasing Methane while preparing foundations, concrete/cement release CO2.) And while many reports mention livestock as emitters of Methane, we humans produce and release methane gas too. The methane is produced by bacteria (methanogens) in the gastrointestinal tract. But it seems that just how much is produced in a person depends fitness, diet and other factors. So there you go fellas, expect a Methane Tax anytime now, Ha ????