LAUSR

Abstract Methanogenesis for generation of renewable energy in geological ecosystems may be influenced by the in-situ iron oxides available. This study investigated the natural iron minerals (Magnetite, Hematite and Specularite) on rate of energy generation and biochemical pathways in the presence of methanol as a model substrate using microbial consortium enriched from oilfield production water. Enhanced (15%) and stimulated energy generation was achieved in the treatments amended with iron minerals compared to the controls without any amendment. The mineral amended treatments resulted in enrichment of bacterial community for Firmicutes, but no changes were observed in the archaea (Methanosarcina mazei). The dynamic changes of acetate and methane concentrations in different treatments during incubation indicated anaerobic fermentation of methanol to acetate occurred prior to syntrophic acetate oxidation coupling with hydrogenotrophic methanogenesis for methane bioenergy production, which was further verified thermodynamically. Iron minerals were suggested to serve as electron donors and conductive networks between syntrophic partners in the microbial community facilitating direct interspecies electron transfer for efficient energy generation. The investigation yielded prospects on efficient generation of renewable energy and environmental sustainability by natural iron minerals. It also provides insights about the key processes in the petroleum reservoirs, deep biosphere and engineered anaerobic systems.