This is a question people are either answering or asking: what are greenhouse gases and what is producing them?
Here I have a chart that shows percentages of gasses in the air. This graph explains clearly where the gases are coming from and what they are. As you can see the most gas exertion comes from power plants, which seems strange because if you look at the separate charts lower you see that most of the methane and nitrous oxide is in fact coming from agricultural by-products but the reason is that there is simply less methane and nitrous oxide than carbon dioxide
On a less serious note, farting animals do affect global warming as they create two fifths of all the methane emissions, that's roughly 14.5 of all emissions
