Okay, here are your Fart Facts. (Other sources mixed in.)
On average, a person produces about half a liter (600 cc) of fart gas per day, distributed over an average of about fourteen daily farts.
A cow, whose diet is totally plant material, produces 300,000-600,000 cc of gas per day. (That's 250 to 500 LITERS!)
According to Dr. James L. A. Roth, the author of "Gastrointestinal Gas" (Ch. 17 in "Gastroenterology", v. 4, 1976) most people (2/3 of adults) pass farts that contain no methane. If both parents are methane producers, their children have a 95% chance of being producers as well. The reason for this is apparently unknown. Some researchers suspect a genetic influence, whereas others think the ability is due to environmental factors. However, all methane in any farts comes from bacterial action and not from human cells.
Scientists say a massive 25 per cent of all methane gas in the world's atmosphere is produced by cows.
It's not the farts as much as it is the burps that contain the high methane content. It's not a fart tax, it's a burp tax!