A data-driven approach to evaluate performance trends across different scales of bioelectrochemical systems

The waste-to-energy nexus has driven the development of bioelectrochemical systems (BES) that utilize electroactive microorganisms to convert waste streams into sustainable energy through extracellular electron transfer mechanisms. In this study, we conducted a data-driven analysis of performance trends in BES across different reactor scales, utilizing 393 data points from 189 studies published over the past five years. The results indicated that major performance metrics of microbial fuel cells (MFCs) and microbial electrolysis cells (MECs), such as maximum current density, maximum power density, hydrogen production rate (HPR), and coulombic efficiency (CE), appreciably declined at larger scales, whereas organic removal efficiency remained stable across varying reactor volumes. The observed decline in performance at larger scales was mainly caused by increased internal resistance, voltage losses, uneven substrate distribution, and electrode fouling. For microbial electrosynthesis (MES) reactors, a small dataset at larger scales, driven by large variations in system design and product selectivity, made it difficult to identify clear trends across scales, underscoring the need for additional larger-scale studies. Proposed strategies to address performance challenges for larger size reactors include the use of electrode configurations optimized to reduce internal resistance and fouling, improved but cost-effective membranes and materials, and the integration of automated monitoring systems. The findings underscore the importance of addressing scale-related electrochemical challenges to advance BES technologies toward practical applications.