Everybody produces gas as a by product of digestion. A normal person will fart 3 to nearly 40 times a day, letting off about 1¾ litres of gas a day. I do not know if this amount is produced in 3 enormous farts or 40 squeaks. We produce a number of gasses, including methane. But the gas that causes the smell is hydrogen sulphide, or bad egg gas, a gas I remember making with my first chemistry set, much to the annoyance of my mother.
Several things make us produce even more gas: low levels of stomach acid,1 meaning that proteins are not properly broken down, so rot as they pass through the nice warm large intestine; eating too much fat -again a digestion issue; food intolerances.
Here are a couple of cooking tips to reduce excessive windy pops: soak beans2 overnight, drain and rinse before cooking. Then add ½ teaspoon of mustard seeds to the cooking water. Cruciferous vegetables like cabbage, broccoli or cauliflower will cause less parping if cooked more quickly, for example, stir-frying instead of boiling or steaming.