How much fart/gas is inside you?

Not very sexy topic

I was out on my long run today and the last 25 minutes I managed to constantly fart. It seemed like an obscene snout of farting. With not much else to think about I wondered how it was possible that a human body could just keep creating enough gas. Normally I just let out 1 or 2 when running, can someone explain how the body works/stores gas?