Check out the MFC-cam, our on-line
demonstration of an MFC!
Renewable and clean forms of energy are one of society's greatest needs. At the same time, 2 billion people in the world lack adequate sanitation and the economic means to afford it. In this research, we are working to address both of these human needs. Energy costs are an important factor in wastewater treatment. In the USA, for example, 5% of electricity we produce is used for the water and wastewater infrastructure (all aspects, including pumping, treatment, etc.), with 1.5% used for wastewater treatment alone.
Microbial fuel cells (MFCs) represent a completely new method of renewable energy recovery: the direct conversion of organic matter to electricity using bacteria. While this sounds more like science fiction than science, it has been known for many years that bacteria could be used to generate electricity. However, expensive and toxic chemicals were needed to shuttle electrons from the bacteria to the electrode and purified chemicals (such as glucose) were needed for the bacteria to grow on. We now know that we can make electricity using any biodegradable material-- even wastewater-- and that we don't have to add any special chemicals if we use bacteria already present in the wastewater. While some iron-reducing bacteria, such as Shewanella putrefacians and Geobacter metallireducens [they reduce Fe(III) to Fe(II)], can be used to make electricity, there are many other bacteria already present in wastewater that can do this.
How does a microbial fuel cell work? When bacteria are placed in the anode chamber of a specially-designed fuel cell that is free of oxygen, they attach to an electrode. Because they do not have oxygen, they must transfer the electrons that they obtain from consumption (oxidation) of their food somewhere else than to oxygen-- they transfer them to the electrode. In a MFC these electrons therefore go to the anode, while the counter electrode (the cathode) is exposed to oxygen. At the cathode the electrons, oxygen and protons combine to form only water. The two electrodes are at different potentials (about 0.5 V), creating a bio-batter (if the system is not refilled) or a fuel cell (if we constantly put in new food or "fuel" for the bacteria).
At Penn State, we are working on developing MFCs that can generated electricity while accomplishing wastewater treatment. In a project supported by the National Science Foundation (NSF), we are researching methods to increase power generation from MFCs while at the same time recovering more of the energy as electricity (See:
Listing of research projects). We have already proven that we can produce electricity from ordinary domestic wastewater (NSF-SGR), as well as many other types of wastewaters including animal/farm, food processing, and industrial wastewaters. (See:
USDA Project). Virtually any biodegradable material can be used to produce power. We support from the
Paul L. Busch Award from the
Water Environment Research Foundation, we hope to improve on the technology and demonstrate it at larger scales (See:
Busch Award). To see a short slide show,
click here. To find out more about this and other hydrogen and fuel cell research at Penn State, visit the
H2E Center webpage. If you'd like to try building a MFC yourself, see the
Make one! page. You may also wish to visit the international MFC website at:
What is the BEAMR/MEC process? By adding a small amount of voltage (0.25 V) to that produced by bacteria at the anode in an MFC, and by not using oxygen at the cathode, you can produce pure hydrogen gas at the cathode! This is a modified MFC process has many different names, including: a "bioelectrochemically assisted microbial reactor" or BEAMR process; biocatalyzed electrolysis cells (BECs); and microbial electrolysis cells (MECs). These names are based on the idea is that fuel cells produce electricity, and electrolysis cells produce hydrogen. This MEC/BEAMR system is operated in a completely anaerobic manner, with the potential produced by bacteria increased by a small amount (using power from an MFC or hydrogen produced by the MEC in a fuel cell). The protons and electrons produced by the bacteria then form hydrogen gas at the cathode-- a process called the hydrogen evolution reaction
(HER). Theoretically we need 0.41 V to make H2 from acetate, and the bacteria produce ~0.2 to 0.3 V. Thus, we only need to add about 0.2 V or more to make hydrogen gas in the MEC/BEAMR. You can read more about this process see the
Links to Public Reports Describing our Research:
This research has been covered by Penn State Press releases, and published in various media (see below). Click on those links for more general descriptions of our findings.