Microbial Fuel Cells — Innovative technology for energy and the environment.

Microbial Fuel Cells

Power generation from microbial fuel cells (MFCs) is an emerging technology with great po-tential for alternative energy applications in envi-ronmental remediation and other areas. MFCs rely on microorganisms to extract electrons from organic compounds (including contaminants) dur-ing biodegradation. They generate electricity by passing electrons to a solid-state terminal elec-tron acceptor (anode). Production of hydrogen used to power hydrogen fuel cells requires addi-tional energy inputs; but, in an MFC, electrons are directly harvested from organic substrates during microbial degradation. The maximum power output of some bench-scale systems var-ies, depending on the substrate type and how the power calculation is normalized, yet achieving ~1.5 W/m2 or ~90 W/m3 is possible with glucose or acetate substrates. MFC as a Power Source

WRI is investigating the feasibility of using an MFC as a trickle charge source for isolated out-door and military applications. Power generated by MFCs is sustainable, green, and very versatile because the fuel source can vary from sugar, to sewage, to groundwater contaminated with petro-leum products. Therefore, the potential for this cutting edge technology is virtually limitless.

A bench-scale MFC system at WRI.

MFCs in Biodegradation

WRI is breaking new ground with our research investigating the feasibility of using petroleum contaminants as substrates in MFCs. We have successfully generated ~120 mW/m2 of cathode using bench-scale MFCs utilizing petroleum hy-drocarbons as the sole substrate (Morris and Jin 2007). To our knowledge, this is the first case of generating electricity from petroleum contami-nants using an MFC. Diesel degradation rates were significantly enhanced over controls with 31% degradation in controls and 82% degrada-tion in a working MFC over 21 days (Morris et al. 2007b). These results are notable because they demonstrate the synergistically enhanced degra-dation of a common contaminant with electricity generation as a “by-product”.

Power generation in an MFC using petroleum hydrocar-bons as the sole substrate (Morris and Jin 2007).

Contact Information: Dr. Song Jin, CHMM Environmental Remediation & Restoration Program Western Research Institute 365 N. 9th St., Laramie, WY 82072 Tel: (307)721-2404 Fax: (307)721-2256 Email: sjin@uwyo.edu

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Alternative Cathode Catalyst

One of the limiting factors of up-scaling MFCs for real world applications is the high cost of materials used in an MFC, such as the platinum catalyst used for oxygen reduc-tion on the cathode. WRI has demonstrated that lead dioxide performs as well or better than platinum and costs substantially less (Patent Pending). This technology has the potential to significantly reduce the cost of large MFC designs and facilitate pilot-scale research in this field (Morris and Jin 2007).

Power density obtained in MFCs using cathodes with a platinum catalyst (yellow and green) or a lead dioxide catalyst (red and black; from Morris et al. 2007a).

MFCs in Multi-Contaminant Degradation

Currently, WRI is exploring a new application for MFCs in environmental remediation: enhanced degradation of petroleum hydrocarbon contami-nants. In our design, MFCs derive electrons from the anaerobic biodegradation of petroleum hydro-carbons, increasing degradation rates by shifting the equilibrium of electron flow. In this case, mi-crobes utilize a solid-state electron acceptor (anode) in the subsurface environment where few terminal electron acceptors are present or less thermodynamically favorable electrons are pre-sent. This design could be used for remediation of contaminated sites as well as a bio-barrier to intercept migrating plumes of contaminants.

Conceptual model of applying MFC technology in situ to enhance petroleum hydrocarbon degradation (Patent Pending).

Innovative and Cutting Edge

WRI is eager to partner with governmental and industrial collaborators to further develop and har-ness MFC technology for real world applications. Our current efforts include:

• Optimizing our MFC design for maximum hydrocarbon degradation and power generation un-der anaerobic conditions.

• Designing and installing an MFC system for groundwater remediation (Patent Pending).

• Developing lead dioxide as an alternative cathode catalyst to platinum (Patent Pending).

Publications

Morris, J.M., S. Jin. 2007. Feasibility of using microbial fuel cell technology in bioremediation of hydrocarbons in groundwater. Journal of Environmental Science and Health-Part A (in press).

Morris, J.M., S. Jin, J. Wang, C. Zhu, M.A. Urynowicz. 2007a. Lead dioxide as an alternative catalyst to platinum in microbial fuel cells. Electrochemistry Communications 9: 1730-1734.

Morris, J.M., S. Jin, B. Crimi, A. Pruden. 2007b. Enhanced Anaerobic Biodegradation of Diesel in a Microbial Fuel Cell. (under review).

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Current density (mA/cm2 cathode)

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Anode/proton bridge matrix.

Surface Cathode