Energy Harvesting Applications of Novel Multi-Electrode Wastewater and Distributed-Benthic Microbial Fuel Cells

Marine exploration is the foundation for understanding ocean systems with autonomous, distributed, underwater communication networks with remote sensing and monitoring. Currently, battery delivered power is the most widely used resource for underwater operations, nonetheless is not sustainable for long-term deployments. Effective energy harvesting from the oceans is critical for ocean exploration, national security, and real-time monitoring, as it is of enormous social and economic value. Benthic Microbial Fuel Cells (BMFCs) could be a low-cost alternative to power remote oceanographic applications by means of harnessing the bioenergy from benthic sediments. Microbially mediated redox reactions, extracellular electron transport processes, and accompanying organic matter degradation are the underlying principles of BMFCs. The dissertation research targeted development of a novel distributed benthic microbial fuel cell (DBMFC) system, to address some of the concerns governing long-term energy requirements for underwater monitoring. In particular, distributed multi-anode/cathode configuration with optimized system design was incorporated for enhanced stability of DBMFCs in the harsh natural environment. Computational model which integrated bio-physiochemical functioning of a BMFC system were incorporated and corroborated with experimental results. Novel carbon-based activated nanofibers (ACNF) anode and bi-layer (BL) platinum-free biocathode: activated carbon cathodes (ACC) were evaluated for their performance in microbial fuel cells (MFCs), BMFCs, and eventually DBMFC systems. In addition, a Power Management System (PMS) system was developed and coupled with batch mode BMFC to augment the output and power working loads. Further, to better understand microbially mediated biogeochemical processes in real time, the consortium associated with BMFC systems were analyzed using molecular biology techniques. The commercialization potential of BMFCs was as well studied to grasp the various application avenues in underwater cyber technology space. The overall performance of the DBMFC system greatly improved over previously demonstrated BMFC systems with a single electrode setup. Stability characterization and computational model simulations confirmed that multi-anode/cathode arrays delivered sufficient power and current yields, whilst arrays were being impaired to mimic adverse environmental bioturbation conditions. ACNF as MFC anode in comparison to the other commonly used substrates (GAC: granular activated carbon, CB: carbon brush, CC: carbon cloth) exhibited excellent prospects for scale up applications in MFC and BMFC systems. Novel activated carbon-based cathodes (ACC) were successfully tested as alternative biocathodes for high stability and improved long-term power generation in BMFCs. The Power Management System (PMS) system was developed and coupled with batch mode BMFC system, augmenting the output load voltage. The finding would significantly improve the efficiency, stability, and durability of BMFC systems to actively power underwater sensor systems and thereby good commercialization prospects. The contributions from the research study integrated numerous lab-scale and field investigations of novel electrode materials, wastewater/ benthic MFC configurations, power management schemes, and microbial ecology analysis. Based on the success of the pilot-scale tests of DBMFCs, the use of novel cost-effective electrode materials integrated with the multi-electrode approach will be the next generation of BMFC systems