Utilization of natural and supplemental biofuels for harvesting energy from marine sediments Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/4m90dz073

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  • A benthic microbial fuel cell (BMFC) is an electrochemical device that generates current from the redox gradient at the sediment-water interface. Early prototypes had anodes buried in anoxic sediments and cathodes in overlying water. The BMFCs described in this dissertation are based on a chamber design that enables the use of high surface-area fiber electrodes and facilitates enhanced mass transport to the anode. Results from Yaquina Bay, OR, show that mass transport resistance accounted for at least 93% of the total internal resistance for a particular BMFC configuration. Power output was increased 18-fold by mechanically induced fluid transport through the anode chamber. At a cold seep in Monterey Canyon, CA, naturally driven advection resulted in a five-fold increase in power from a BMFC with low-pressure check valves relative to an identical BMFC with high-pressure check valves. Enhanced transport coincided with a change in the microbial community on the anode from one dominated by epsilonproteobacteria to one with relatively even representation from deltaproteobacteria, epsilonproteobacteria, firmicutes and flavobacterium/cytophaga/bacterioides. Laboratory experiments investigated the effect of adding supplemental carbon sources to anode chambers. Repeated lactate injections appeared to stimulate sulfate reduction resulting in short term power gains but did not apparently shift the process responsible for baseline current. When a specific inhibitor of sulfate reduction was added, lactate-supplemented and unsupplemented BMFCs performed similarly. BMFCs have been proposed as power sources for monitoring systems in remote locations. Practical implementation of this technology is governed by three conditions: 1) low-voltage current must be stepped up to meet the requirements of off-the-shelf electronic devices, 2) modest power production and variable power demands require integrated energy storage, and 3) BMFCs should be operated at the most efficient potential for energy production. A combination power converter/potentiostat/rechargeable battery system was described based on these considerations and tested with a chambered BMFC in Yaquina Bay, OR. The BMFC provided intermittent power to an acoustic receiver, and results highlight the need to increase power, make design improvements to better seal the chamber to the sediment and increase the capacity for energy storage.
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