Wastewater

(Energy Neilcy). Power can also be obtained from sewage water. The technique used herefore are Microbial fuel cells. Also using the same microbial fuel cells, instead of from wastewater, energy may also be obtained directly from (certain) aquatic plants. These include reed sweetgrass, cordgrass, rice, tomatoes, lupines, algae [28]

Source :http://en.wikipedia.org/wiki/Renewable_energy