Optimized materials for microbial electrolysis cells operation in anaerobic digestion environments

This study aims to improve the operation of microbial electrolysis cells in anaerobic digestion environments by selecting and benchmarking cell components (bioanodes and separators) to enhance performance when using real, complex substrates. The thesis began with a comprehensive review of the current state of MEC technologies, identifying critical challenges, like low electrical performance and issues related to separators, such as additional overpotentials and pH imbalances, when operating in real complex substrates. To address these challenges, two experimental investigations were conducted.
In the first study, various bioanode materials were compared under conditions designed to mimic those encountered in anaerobic digesters. Different carbon-based materials were evaluated alongside stainless-steel-based electrodes, and two inoculation strategies were tested using either pure cultures of electroactive microorganisms or a naturally mixed microbial community. It was demonstrated that stainless-steel wool electrodes generated higher current densities and maintained greater operational stability than traditional carbon-based options. In addition, the influence of different degrees of substrate fermentation on bioelectrochemical performance was investigated, providing deeper insights into the interplay between material properties, substrate fermentation level and electrical output.
In the second study, the evaluation of separators—a critical component influencing overall cell efficiency—was undertaken. Commercial ion-exchange membranes (both cation and anion types) were tested, and an innovative alternative, a PDMS-modified cellophane separator, was explored. Parameters such as ionic resistance, pH imbalances, and organic acid crossover were assessed under realistic anaerobic digester conditions. It was found that while traditional membranes perform well in synthetic media, their performance tends to decline when exposed to real waste streams.
Finally, the outcomes of both studies were synthesized to develop a comprehensive understanding of the critical factors influencing MEC system performance in anaerobic digestion environments. It was concluded that a balance between cost-effectiveness, durability, and efficiency can be achieved through the careful selection and optimization of both electrode and separator materials. The work provides a roadmap for future research, emphasizing the need to test these components under realistic operational conditions to fully harness the potential of MEC systems for sustainable energy production and waste valorisation.