What's Next In Science & Technology

Environmental scientists at Washington University in St. Louis has created a device similar to a hydrogen fuel cell that uses bacteria to treat wastewater and create electricity.

Scientists have devised a microbial fuel cell which called an upflow microbial fuel cell (UMFC) that is fed continually and, unlike most microbial fuel cells, works with chambers atop each other rather than beside each other.

Electricity has been created with the device ? in its current mode, about the size of a thermos bottle ? and it has to be scaled up considerably to someday handle the two million or so gallons of wastewater it needs to treat to churn out enough power.

"We have proven we can generate electricity on a small scale. It will take time, but we believe the process has potential to be used for local electricity generation.

"The upflow microbial fuel cell is a promising wastewater treatment process and has, as a lab-scale unit, generated electricity and purified artificial wastewater simultaneously for more than five months."

The fuel cell uses a carbon-based foam with a large pore size on which biofilm grows, allowing the connection of two electrodes in the anode and cathode chambers with a conductive wire. In a hydrogen fuel cell a membrane separates the anode and cathode chambers. When hydrogen meets the anode electrode, it splits into protons and electrons, with protons going across the membrane to the cathode chamber, and electrons passing over the wire between electrodes to create a current. Oxygen is added to the cathode chamber, and on the electrode there is a reaction of electron plus proton plus oxygen to form water. Catalysts, such as platinum, are needed on both electrodes to promote the reactions.

"We are doing basically the same thing as is done in a hydrogen fuel cell with our microbial fuel cell. We've found that the bacteria on the anode electrode can act as the catalyst instead of platinum."

"The bacteria form a biofilm on the anode electrodes, and what I want to do is optimize this process so that we get higher currents, which should allow us to scale up the system."

Scientists say that producing energy from wastewater should be a high international priority because of population growth and worldwide depletion of energy resources.

Wastewater, with its high-content organic matter, also can produce methane and hydrogen fuels. However, more readily usable energy can be produced when electricity is produced directly in a microbial fuel cell.

A bioelectricity generating wastewater treatment system in just one large food-processing plant could power as much as 900 American single-family households.