Applied Electrochemistry

Our laboratory is applying electrochemical methods to study biogeochemical processes (e.g., microbial mechanisms of electron transport, organic matter, methane and pyrite oxidation) and to develop microbial fuel cells as power sources for ocean instrumentation.

Ocean and Seafloor Microbial Fuel Cell Projects

Reimers et al. (2001) and Tender et al. (2002) demonstrated that graphite electrodes placed at least a few centimeters on either side of the sediment-water interface in coastal environments can generate sustainable electrical power due to electrode reactions that are both microbial and geochemical. Early diagenetic processes separate the primary reactants (organic matter, sulfides and oxygen) and maintain the potential difference necessary to channel electrons through an external circuit. In this way the electrodes and their surroundings function as a seafloor (or benthic) microbial fuel cell.

We are working to evaluate limiting factors for these fuel cells and testing prototypes under different geochemical conditions (e.g., in different environments, and with and without supplemental sources of organic acids, sulfide and methane). Our newest designs place the anodes above the sediment-water interface in benthic chambers that can be pumped to enhance the supply of reductants responsible for power production (Nielsen et al., 2007). We are also exploring the generation of electrical energy from energy-rich planktonic biomass and detritus intercepted before decay in the water column (“Plankton Power”; Reimers et al., 2007). It is our expectation that new microbes important to the transfer of electrons will be found in both plankton and sediment powered systems, as will new microbial community associations. We are in the process of identifying these microbes, studying their geochemical impacts, and using the results to document fundamental biogeochemical processes and to optimize microbial fuel cell performance.

Laboratory microbial fuel cell experiments using batch additions of marine plankton.

Current field experiments are also documenting the efficiencies of DC-DC conversion methodologies as voltages are stepped up to power environmental sensors such as hydrophones. Collaborating in different aspects of this work are Drs. Peter Girguis (Harvard, microbiology), John Westall (OSU, electrochemistry), Peter Kauffman (NW Metasystems, electrical engineering), Bart Chadwick and Ken Richter (Navy SPAWAR, San Diego, sensor applications).  This research is supported by the US Office of Naval Research.

Deployment of a chambered benthic microbial fuel cell in San Diego Bay. The fuel cell is being used to power a sonic receiver that records encounters with tagged sea turtles.

References:

Nielsen, M.E., Reimers, C.E., and Stecher, H.A., III (2007) Enhanced power from chambered benthic microbial fuel cells. Env. Sci. & Technol. 41, 7895-7900.
                       
Reimers, C.E., Stecher, H.A., III, Westall, J.C., Alleau, Y., Howell, K.A., Soule, L., White, H.K., Girguis, P.R. (2007) Substrate degradation kinetics, microbial diversity, and current efficiency of microbial fuel cells supplied with marine plankton. Appl. Envir. Microbiology 73, 7029-7040.

Reimers, C.E., Tender, L.M., Fertig, S., and Wang, W. (2001) Harvesting energy from the marine sediment-water interface. Environ. Sci. Technol. 35, 192-195.

Tender, L.M., Reimers, C.E., Stecher, H.A., III, Holmes, D.E., Bond, D.R., Lovley, D.R., Lowry, D.A., Pilobello, K. and Fertig, S. (2002) Harnessing microbially generated power on the seafloor. Nature Biotechnology, 20, 821-825.