University Park, Pa. -- Using a new electrically-assisted microbial fuel cell (MFC) that does not require oxygen, Penn State environmental engineers and a scientist at Ion Power Inc. have developed the first process that enables bacteria to coax four times as much hydrogen directly out of biomass than can be generated typically by fermentation alone.

From: http://live.psu.edu/story/11709

Photos available at http://www.psu.edu/ur/2005/hydrogensourcephotos.htm

I'm sure many of you have seen this but I thought I'd post it. Not only for the space exploration "closed loop life support" angle but also just for personal use. Imagine having a system like this set up in a septic tank. The electricity could be provided from a solar cell as the voltage needed is so small. Then a small system to catch the H2 and CO2 and crank that back into easily stored CH4 via the Sabatier process or something like it. I bet the amount of gas produced wouldn't be prolific but as a renewable source of energy, it MIGHT be worth it.