You should make mobs (cows, mooshrooms, pigs, sheep, etc.) occasionally poop. Why you ask? Too pick it up and convert it into EU, of course!
Recipes : (P = paper) (RP = Refined Poo)
P P
P P
P P P = Bag, to pick up the poo with.
Smelt poo to get refined poop.
RP RP
= Methane Generator
Put an empty cell into the Methane Generator to get one Methane Cell.
This is pretty much it. I know hardly anything about EU and Methane so I will let you decide what the necessary amount of EU it gives off. I'll update the thread if I think of anything else
Also, if anybody would like to make a suggestion, quote this and suggest it