APPLICATIONS OF SEDIMENT MICROBIAL FUEL CELLS

Timothy Ewing

Devices that use microorganisms capable of transferring electrons to or from an electrode are classified as bioelectrochemical systems. A well-known sub-category of bioelectrochemical systems are sediment microbial fuel cells (SMFCs). SMFCs are assembled from two electrodes, an anode and a cathode, and generate electricity from the redox potential gradient in natural or engineered aqueous systems. At the anode in the anaerobic sediment, electrogenic microorganisms oxidize organic carbon compounds to carbon dioxide, protons and electrons. The protons diffuse out of the sediment and the electrons are transferred first to the anode and then through a conductive circuit to the cathode. At the cathode in the aerobic aqueous layer, oxygen is the terminal electron acceptor to complete the circuit. The proposed practical application for SMFCs has been narrowly focused as a renewable energy source for remote sensors. Whether powering sensors at the bottom of the ocean or in remote ecologically sensitive environments, SMFCs could provide a long-term low maintenance solution to traditional batteries. The challenges to utilizing SMFCs include low power generation, slow start-up, ineffective scale-up, and a lack of long term knowledge of operation and microbial community structure. The objective of this dissertation was to develop technologies to advance sediment microbial fuel cells to become a viable technology to be used for applications including powering remote sensors and enhancing wastewater treatment. First, technologies were developed to start up SMFCs faster and evaluate the long-term operation. Second, a novel technology was developed to scale-up energy harvesting from SMFCs. Finally, a new SMFC application area for self-starting, self-powered wastewater treatment of agricultural wastes was developed. Overall we solved several SMFC limitations by increasing both short-term start-up power and long-term steady-state power compared to control systems. We characterized the microbial community and concluded that addition of an electron donor can change the community structure but operation of a power management system did not change the structure. In addition, we showed that SMFCs can be applied to a new area of wastewater treatment through the use of an innovative self-powered aeration system.

APPLICATIONS OF SEDIMENT MICROBIAL FUEL CELLS

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