Microbial fuel cells can also be used in the bioremediation of water containing organic pollutants such as toluene and benzene, compounds found in gasoline. The MFC design is altered so that the fuel cell floats on top of polluted water. The anode is submerged in the water where organic pollutants feed the bacteria while the cathode floats on top of the water. The organic pollutants are decomposed to carbon dioxide and water, cleansing the polluted lake or stream. The MFC can be left alone in remote natural bodies of water, just like the remote sensor [9]. A working prototype shown in Fig. 7 has been deployed in a polluted marsh in Mexico and is beginning the process of cleaning up the worlds remote rivers.