With energy prices near all-time highs, teams of researchers across the world are looking for other sources of power. One such team is located here at UW-Madison, where scientists from several disciplines have been working together to help alleviate our global energy crisis.
Instead of designing new power stations, however, the UW-Madison team is working on using so-called microbial fuel cells to add power generation abilities to existing water treatment facilities.
Daniel Noguera, UW-Madison professor of civil and environmental engineering, said nature has already been working on the energy problem for millions of years. ""[Photosynthetic] bacteria have highly tuned mechanisms for harnessing the sun,"" he said. ""All we need to do is provide them with nutrients.""
By placing the bacterial fuel cells in a wastewater treatment system, Noguera's team hopes to provide the microorganisms with an essentially free source of nutrition.
""We treat the wastewater anyway, [and] you are using a lot of energy to do that,"" he said of the nutrient source.
Traditional fuel cells have received a lot of recent attention in the press due to high profile technology demonstrations by car manufacturers. The concept behind these Proton Exchange Membrane cells is simple: Hydrogen is placed in a chamber with an anode and oxygen in a chamber with a cathode. A porous membrane with a catalyst separates the two chambers, and a current is produced as the hydrogen and oxygen combine to generate water.
Marc Anderson, UW-Madison professor of civil and environmental engineering—along with Senior Scientist Isabel Tejedor-Anderson—have worked extensively with PEM cells before and are contributing their material science expertise to the project.
""The issue [with traditional cells] is storage,"" Anderson said. ""Since PEM cells require highly pressurized sources of hydrogen and oxygen, there is a real safety hazard.""
Microbial fuel cells do away with the need for expensive and bulky safety precautions. Extra electrons and protons are produced as a by-product of the photosynthetic process, and can be harnessed to react with oxygen similarly to the process in PEM cells.
However, since components of the fuel cell are now biological, the materials used in the cell must be modified.
""Commercial fuel cells use polymeric membranes [to separate elements],"" Tejedor-Anderson said. Polymeric membranes, while ideal for PEM cells, are not suitable for use in a biological environment.
""We have spent a lot of time redesigning our fuel cells to optimize the power density,"" said Tejedor-Anderson.
The idea of using bacteria to generate power is not a new one. In 1912, M.C. Potter, a professor of botany at the University of Durham, England, extracted small amounts of electricity from E. Coli, a common intestinal bacteria.
Although researchers throughout the following decades were capable of producing series of cells that generated 35 volts of electricity, the current was unreliable due to the unstable nature of the organisms involved.
However, insights into the biological processes that take place within electrochemically active bacteria have spurred new research within the field. Now, several universities including Penn State and Washington University in St. Louis host groups of scientists developing several different applications of the technology.
The final product of the work being done at the UW-Madison would not be limited to a large facility. According to Noguera, the technology is scalable and, once commercialized, could easily be adapted to generate electricity from backyard compost piles or landfills.
Although steps have been made toward commercializing the technology, the research is far from complete. Current prototype cells generate roughly half the voltage that theory predicts, and produce a current that is orders of magnitude smaller than other more traditional fuel cell technologies.
""The problem is efficiency,"" Noguera said. ""We must discover the right combination of organisms to generate the most power.""
Other challenges include designing a system to provide sunlight at a near constant rate, despite changing outdoor conditions, as well as an energy efficient method to integrate the fuel cells into the wastewater treatment system.
