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Renewables > BioenergyCapturing Electrical Current via Microbes to Produce Methane
Start Date: September 2011
Alfred Spormann, Departments of Chemical Engineering, and of Civil and Environmental Engineering, Stanford University; and Bruce Logan, Department of Civil and Environmental Engineering, Pennsylvania State University
The focus of this research is to gain a fundamental understanding of the biology and ecology of methane-producing (methanogenic) microbial cultures for use in a microbial electromethanogenesis cell (MEMC). When fully implemented, the proposed MEMC will result in the cost-effective, carbon-neutral production of methane from atmospheric CO2 using electrons generated from renewable energy sources. The research will advance the science and the technology of the MEMC process and the ultimate commercialization of this technology.
Methanogens are single-celled organisms that use electrons to convert carbon dioxide (CO2) into methane. Bruce Logan demonstrated that methane can be produced by a process called electromethanogenesis using a biocathode containing methanogens. The basic MEMC design is shown in Figure 1. This scheme includes multiple and alternative scenarios for how such a system can operate.
While conceptually simple and attractive, there are significant hurdles to overcome before a microbial-based electricity-to-methane technology can be deployed. One of the most critical and least understood areas is the microbiology at the cathode. Efforts to identify key methanogens in large microbial cultures have been inconclusive. Moreover, important advancements in electrode and microbial electrochemical cell design are required to develop a deployable technology.
A key goal of the project is to understand the long-term ecological and evolutionary fate of microbial electromethanogenesis processes. Methanogenic and methane-consuming microbes can be found in a number of naturally occurring aerobic-anaerobic interfaces, often in a mutualistic ecological relationship. The underlying hypothesis of this project is that aerobic methane-consuming bacteria play an important supporting and stabilizing role in a robust MEMC cathodic chamber. This research will directly address this hypothesis by investigating the role of these bacteria in stabilizing defined methanogenic microbial communities at the cathode. The main research tasks include the isolation of single strains or defined microbial communities capable of sustained cathodic methanogenesis, and to design and test advanced electrode systems (Figure 2). Cathode surfaces will be chemically modified to increase the electrical conductivity and reduce contact resistances based on successful approaches with bacterial biofilms. Materials that have higher surface areas and avoid the need for precious metal inorganic catalysts activity for oxygen evolution at the anode will be examined.
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