Bioelectrochemical hydrogen production from agro-industrial wastewater: key breakthroughs and challenges

The growing gap between global energy demand and the shortfall in energy production is becoming more critical because of the depletion of fossil fuel resources. However, these energy sources are not only limited, but they also pose serious threats to the environment and life on Earth. This has sparked a strong push to explore alternative energy carriers. This transition toward sustainability has focused on the potential of bioelectrochemical systems (BESs), notably microbial electrolysis cells (MECs), as a promising approach to the sustainable production of hydrogen, leveraging the dual merits of renewable energy generation and wastewater treatment. Due to their high organic load and availability, agro-industrial wastewater represents a suitable substrate for MEC-driven hydrogen production. Exploiting these wastes not only contributes to an abundant and cost-effective resource but also responds to critical environmental challenges associated with wastewater management. This review explores the intersection between bioelectrochemical hydrogen production and agro-industrial wastewater treatment, focusing on current advancements and developing patterns in this field. A comprehensive analysis of MEC technology is presented to investigate the effect of key progressions including reactor components and experimental parameters on system performance. Moreover, the role of microbial consortia and the influence of wastewater composition are critically analyzed. Furthermore, this review examines the current challenges including substrate variability, biofilm development, and scaling up from laboratory to industrial applications and outlines strategies to overcome them. By handling these delays, MEC technology could advance toward industrial implementation, paving the way for sustainable hydrogen production from agro-industrial wastewater streams.