Simone Colantoni; Óscar Santiago; Janek R. Weiler; Melanie T. Knoll; Christian J. Lapp; Johannes Gescher; Sven Kerzenmacher

Journal of Environmental Chemical Engineering  12  (2024) : 113071

doi: https://doi.org/10.1016/j.jece.2024.113071

Integrating microbial electrolysis cells (MEC) with anaerobic digestion (AD) would offer different synergistic advantages to these technologies. The MEC bioanode could be immersed in the AD reactor, stabilizing the process, or operated as an independent cell, further removing organic matter. However, up to now, bioanodes operated in anaerobic digestion conditions present low current production and tend to deactivate over time. In the present work, we conducted a comparison of six carbon-based and metal-based electrode materials, including novel options such as stainless steel wool (SSW) and carbon nanofibers (ES300), never tested before under these conditions. The electrodes were evaluated using two inoculation procedures, operating simultaneously in the same electrolyte with different feeding media. The bioanodes produced double the current densities when fed with undigested corn silage compared to anaerobic digester effluent, showing the potential for direct integration into anaerobic digesters without pre-fermentation. Unprecedented stable current densities, up to 0.4 mA cm−2, were obtained over 60 days of operation in real anaerobic digestion conditions by Geobacter-dominated bioanodes on SSW and ES300, outperforming state-of-the-art bioanodes and avoiding the dramatic deactivation previously reported. Microbial community analysis of SSW and ES300 elucidated how the microbial composition in the bioanodes was mostly depending on the electrode material, rather than the inoculation procedure. The results achieved with these bioanodes pave the way for scaling up and commercializing integrated AD-MEC systems.

 © 2024 The Authors ( CC BY 4.0 )