http://www.azom.com/details.asp?newsID=6268In the midst of the worldwide energy crisis, researchers at Washington University in St. Louis have been continuing their work on a microbial fuel cell that generates electricity from wastewater. Advances in the design of this fuel cell in the last year have increased the power output by a factor of 10 and future designs, already in the minds of the researchers, hope to multiple that power output by 10 times again. If that goal can be achieved, the fuel cell could be scaled up for use in food and agricultural industries to generate electrical power - all with the wastewater that today goes right down the drain.
Lars Angenent, Ph.D., assistant professor of chemical engineering, and a member of the University's Environmental Engineering Science Program has devised a continually fed upflow microbial fuel cell (UMFC). In a paper published online in the Environmental Science Technology, Angenent describes how wastewater enters from the bottom of a system and is continuously pumped up through a cylinder filled with granules of activated carbon. Many previous microbial experiments used closed systems with a single batch of nutrient solution, but because this system is continuously fed from a fresh supply of wastewater, Angenent's UMFC has more applications for industry since wastewater is continually outputted during industrial production.
The organic matter in the wastewater provides food for a diverse community of bacteria that have developed a biofilm (a thick-layered colony of bacteria) on a simple electrode in the anode chamber. An inexpensive U-shaped proton exchange membrane inside the anode chamber separates the anode from the cathode.
As the bacteria feed on the organic material in the wastewater they release electrons to the anodic electrode. These electrons then move to the cathodic electrode via a copper wire. The formed protons are transferred through the membrane towards the cathode where they react with electrons and oxygen to form water.
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