It's Hunan, not hunam.
Hunan waste includes methane because cats are mammals. If you ever buy chicken at one of those places, you are really eating cat. They probably dump the spare cat parts down the crapper and it gets into the septic system. They can't put it in the dumpster or the health department would catch them.
Lighting farts on fire proves the point. If you had eaten chicken, which is a bird, your fart would not light. You ate cat, a mammal, and now it lights. My advice would be to stick to KFC.