Of those fart components, hydrogen, hydrogen sulfide, and methane can all be set on fire. Yes, there's methane present, but it's a small part of the equation and generally isn't the reason people are capable of turning their butt into a putrid roman candle.
To some extent, you can actually tell what's in a fart by the flame's color. The flame from a fart where hydrogen is the primary fuel will burn yellow or orange, while an atypically high methane content will turn the flame blue. If you've spent any time looking at YouTube videos of fiery toots, you've almost certainly noticed these candles in the wind are usually yellow or orange. Few are the blue angels of YouTube.