If you are using gregtech, practically everything can be turned into power in some sort of fashion. If you have MFR farms running and producing sludge, send it to a sludge boiler. The sludge boiler has a high chance to produce clay. The clay can be be turned into lithium. and the lithium can be turned into fuel. Steam is also a good option with gregtech. Last time I used GT, I added the steam upgrades to all my normal machines and ran everything off steam directly --much simpler wiring (the MV and HV systems couldn't get enough steam through a single fluiduct connection though).
The nether bees can produce phosphor, which when combined with sand, can produce lava. A few alvearies with them can produce tons of phosphor. Take the lava and dump into the upgraded geothermal generators from GT. 30k eu/tick.
I often run a mish-mash of power generators with GT. There are so many things that can be turned into power, it's kinda unreal. Between the industrial centrifuge and chemical reactor, almost everything can be processed into something else more beneficial. GT has lots and lots of steps to producing items though, so it is very rarely a one step process to good power generation.