Heh well your in luck I rerecorded the first ep today to correct that problem and I explained how I think wastegas can work a bit more.
Think about a stomach that breaks organic compounds down then leaches off the methane. You could make it two stage, one is a harsh chemical to break down the organic compound then it dumps it into genetically modified yeast to devour the organic goo. I dunno but it might be able to work or blow up the engine!
http://digitalundernet.com/mirror/DJ/TheDJEp1-WastelandGangs.mp3Also I took the other one down because it was horrid
EDIT: if you were to make a wastegas engine like I'm thinking of you car would effectively SHIT or fart if you burn it might not be as great as I thought