Electricity can be harvested from sewage microbe. This is a long shot, but it is interesting perspective on sewage as a source rather than waste and a burden.
Stanford scientists have developed a "battery" that harnesses a special type of microbe to produce electricity by digesting the plant and animal waste dissolved in sewage. Credit: Xing Xie,Stanford Engineering
Read more at: http://phys.org/news/2013-09-microbial-battery-team-wired-microbes.html#jCp
