Development and deployment of a surface based benthic micorbial fuel cell

Benthic microbial fuel cells (BMFCs) have the potential to provide long-term, sustainable power for undersea devices. BMFCs operate by harnessing organic matter in the sediment as a fuel source. Field systems have demonstrated power densities in the range of 5 to 20 mW/m² depending on size and operating conditions. Operation of anodes under anaerobic conditions is critical to the functionality of BMFCs because the presence of oxygen will negatively affect the microbiology and chemistry driving power production. In order to provide an anaerobic environment the BMFC anodes are usually buried at least 10 cm under the sediment which generally ensures a completely anaerobic environment in reducing coastal sediments. Furthermore, to increase a system´s power output, large surface areas for the anode and cathodes are needed. Installation of these large-scale anodes is difficult, time consuming, and in the case of very deep water environments, almost impossible. In order to solve the issue of complex burial techniques for large anodes, a unique design of BMFCs has been created which allows the anode to be placed on the sediment surface without being buried and still operate under anaerobic conditions. Carbon cloth anodes were covered on one side with metalized plastic film, specifically biaxially-oriented polyethylene terephthalate (BoPET), and sealed at the edges. This type of metal film has very low oxygen permeability which prevents oxygen in overlying water from diffusing through the film and interfering with current production at the surface of the anode. Weights were added to the perimeter of the film in order to ensure a seal between the anode edge and the sediment to prevent aerobic seawater from contacting the anode thus ensuring an anaerobic environment for the anode. The concept was tested at various scales in the lab environment and a prototype deployment system was developed and tested for future scale-up and field applications.