A normal person passes wind between 10 and 20 times a day. Obviously some of us keep that average high, but still, you have to wonder: where does all that flatulence come from?
While some of the gas you pass does come from swallowing air, the bulk of it is a result of the bacteria in your gut, as they chomp through the undigested contents of your intestine. This video from TED gets to the bottom of what causes excess gas production and, perhaps most importantly, the vile smells that occasionally waft your way. [TED Ed]