The Seafloor Bio-Fuel Cell: Long-Term Power and Effects on Sedimentary Organic Matter

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P.I. Reimers, Clare (OSU) Proposal #: 0242048Proposal Title: The Seafloor Bio-fuel Cell: Long-term Power and Effects on Sedimentary Organic MatterProject Summary The long-term goal of this research is to fully develop seafloor bio-fuel cells so they may outperform batteries as the power source for many forms of autonomous marine instrumentation. Electrochemical devices placed across the sediment-water interface can harvest low- levels of power for long periods of time by using natural, continually renewed, chemical resources in sediment as fuel and dissolved seawater oxygen as oxidant. This new technology functions much like a microbial fuel cell, taking advantage of the voltage gradient that occurs in the top few centimeters of the sediment column. Bacteria that ordinarily shuttle electrons to substrates such as FeOOH or S0 have been shown to attach to the buried electrode (anode) as a biofilm. These microorganisms are suspected to generate electricity by direct reduction of the anode. In this proposal the PI outlines engineering and science goals to advance the seafloor bio-fuel cell closer to future applications. Specifically the goals are to: (1) assemble a surface-ship-deployable prototype that will lead to devices that are both a power source and bottom weight for a sensor mooring, (2) run both short and long-term performance tests of prototypes in environments targeted for ocean observatory science, (3) evaluate the effects of continuous versus cyclic energy harvesting on performance during tests, and (4) understand linkages between performance, microbial enrichments and organic matter oxidation. An underlying assumption that will determine the ultimate utility of these power sources is that seafloor bio-fuel cells can tap nearly all the chemical energy stored as organic matter in anoxic sediments. In other words, seafloor bio-fuel cells should generate the same degree of organic matter remineralization as chemical oceanographers have termed the oxygen effect. To test this premise and accomplish these goals, the PIs propose two cruises to stations on the Oregon continental shelf and rise. During each cruise measurements necessary to quantify background sedimentary organic matter remineralization processes and oxygen-exposure history will be performed. Four bio-fuel cell devices will be deployed, recovered after 3-day tests then redeployed for up to one year at each site. Sediments will also be collected for laboratory experiments with two-chambered bio-fuel cells.