I've considered that... But on the plus side, the so-far-non-ignitable gas tends to be non-injurious to those in the vicinity. I worry that adding dietary elements that foster greater flammability would also increase the danger to those nearby. Even if no one is around, I worry about peeling the paint -- I had a friend long ago whose flatulence was legendary, and I have no great desire to try to out-do him. :-)
Well, the local bird population is thankful.