Yes it does.
That's why fart lighting works. We don't produce as much as a cow, perhaps, but we do produce it. What makes them smell bad is skatole, a naturally occurring compound in poo.

There is also debate as to whether you're lighter after farting, or heavier- methane being lighter than air, it provides a miniscule amount of buoyancy. But is that buoyancy more than the weight of the methane? Inquiring minds want to know.
( The Resident Loon Not a demographic. Do not measure., Mon 17 Sep 2012, 14:59, Reply)