A Rwandan prison uses human excrement as an energy supply. The poop is sent to a "digester," which is chamber where bacteria eat the poop and expel it as methane. The remaining poop is used as an odorless fertilizer.
Technical fact from the article: "The lead engineer on the project, Ainea Kimaro, says that within four weeks, 100 cubic meters of waste can be transformed into 50 cubic meters of fuel."
http://www.wired.com/news/planet/0,2782,68127,00.html?tw=wn_3techhead
