| Abstract | Microbial electrolysis cell–assisted anaerobic digestion (MEC-AD) is an emerging technology with the potential to enhance biogas yields and selectively increase methane content through bioelectrochemical stimulation. However, practical deployment remains constrained by long start-up times, reactor instability, and inconsistent methane enrichment, largely driven by poorly understood microbial community dynamics. This ongoing work aims to decipher the structure–function relationships of microbial consortia in MEC-AD reactors to inform targeted strategies for improved start-up, troubleshooting underperforming systems, and maximising the proportion of methane in the biogas produced. Using a combination of microbial community profiling and reactor performance analysis, we investigate the interplay between electroactive bacteria, fermentative microorganisms, hydrogen producers, and methanogenic archaea under MEC-AD operating conditions. Particular emphasis is placed on hydrogen-mediated interactions, as the balance between hydrogen production and consumption is critical for steering methanogenesis and direct electron transfer mechanisms. To this end, we explore bioaugmentation strategies involving the supplementation of reactors with selected hydrogen-producing microorganisms, electroactive bacteria and hydrogenotrophic methanogens, with the objective of stabilising syntrophic interactions and enhancing methane productivity. Preliminary metagenomics analysis of inocula taken from an MEC-AD reactor fed with energy crops indicated established hydrogenotrophic methanogenesis (Methanoculleus), diverse fermentative and syntrophic bacteria, and high functional diversity that may confer robustness. However, the relatively modest abundance of hydrogenotrophic methanogens compared to the total community supports the rationale for targeted bioaugmentation (e.g. with hydrogen producers and Methanoculleus-like methanogens) to further steer methane enrichment and accelerate reactor start-up or recovery. This work is currently ongoing. Ultimately, this research seeks to translate microbial ecology insights into the rational design of tailored inocula that can be immobilised and deployed for bioaugmentation in MEC-AD reactors. Such engineered inocula could provide a practical route towards faster start-up, improved robustness, and higher-quality biogas, supporting the wider implementation of MEC-AD systems for sustainable waste-to-energy applications. |
|---|