Improved methane production and COD removal from food waste in anaerobic digesters incorporating microbial electrolysis systems
Anaerobic digesters (ADs) are widely used to recover energy from biomass waste. Microbial electrolysis cells (MECs) have been proposed for incorporation into ADs to improve methane production, while the responses of MEC-assisted ADs (MEC-ADs) to changes in operational conditions have not been sufficiently examined. Here, we operated laboratory ADs and MEC-ADs using food waste as feed, and organic loading rates (OLRs) were adjusted. Analyses of AD performances, including methane production and COD removal, show that MEC-ADs exhibit higher performances than ADs at OLRs of 7 g COD L-1 D-1 or higher. In addition, pH was stably maintained in MEC-ADs at high OLRs. Metabarcoding of rRNA gene amplicons showed that Desulfuromonadaceae bacteria were enriched at the anodes in MEC-ADs, while Methanobacteriaceae archaea were increased at the cathodes. It is suggested that the MEC system is useful for the stable operation of ADs, especially at high OLRs.