People who swallow a lot of air fart more than people who don't.
Scientific studies of farts show that women's farts have a higher concentration of odor-causing gases than men's farts, but men's farts have a larger volume. The two factors equalize out (the same number of stench molecules for both), so the odor is about the same.
People even fart shortly after death.
The butt is the location of the anus in humans, and by definition, a fart is an anal escape of intestinal gas. We should be grateful that we are not crinoids. The crinoid is a marine creature with a U-shaped gut, and its anus is located next to its mouth.
Beans contain sugars that we humans cannot digest. The most offensive sugars, known as "flatulence factors" to scientists who research farts, are raffinose, stachiose, and verbascose. When these sugars reach our intestines, the bacteria go wild, have a big feast, and make lots of gas!
Farts burn because they contain methane (sometimes) and hydrogen, both of which are flammable gases.
Farts burn with a blue or yellow flame.
http://www.heptune.com/farts.html
