Efficiency improvement of microbial fuel cell through the isolation of a novel effective electrogen aeromonas caviae and development of a M2FC reactor system

Abstract

Microbial Fuel Cell (MFC), a fuel cell using microbes as catalysts, can produce electricity directly from organic compounds even wastewater and thus consider a promising option for renewable energy and wastewater treatment. However, the technology is still at an early stage, requiring serious further research for its field implementation. The primary goal of this thesis was to improve the efficiency of MFC technology, for which two different topics were explored. The first one was to isolate new efficient electrogen (microbial catalysts) from various sources. One electrogen isolated from ostrich and giraffe dung, named $\It{Aeromonas caviae}$, was found to be sufficiently efficient. This microbial species generated higher electricity than electrogens from sludge samples, which are typical inocula for the MFC operation ($388mW/m^{-2}$ versus less than $200mW/m^{-2}$of power density). The second topic was to construct a novel MFC reactor to improve efficiency and sustainability of the MFC. For that, a cathode part was newly designed, so that the new system consists of ferric based MFC and ferrous based fuel cell (FC). Through the circulation of iron ion between MFC cathode part and FC anode part, iron ion could be regenerated with additional power generation. When the ferric based MFC was separately operated, the power was maintained only for 4 days due to the depletion of the cathodic terminal electron acceptor (catholyte). However, when being connected to the ferrous based FC, the whole system was maintained stably for the entire experimental period (200 hours), producing $3 \sim 20 times$ more power than a similar system, i.e., a dissolved air cathode MFC.