Advancing psychrophilic anaerobic digestion reactor design through biotic and abiotic insights

Abstract

Psychrophilic anaerobic digestion (<25 °C) offers significant advantages in terms of reduced energy input and suitability for cold regions compared to mesophilic (30–40 °C) and thermophilic (50–60 °C) conditions. Despite extensive efforts to improve psychrophilic anaerobic digestion, the existing literature is diverse and fragmented, limiting the understanding of the roles and effects of biotic and abiotic shifts critical to these systems. To address this gap, this study reviewed critical issues for the transition from mesophilic/thermophilic to psychrophilic conditions, focusing on the biotic and abiotic factors, including the physical and chemical properties of multiphase systems, mass/electrons transfer, microbial community structures, enzyme activities, and the thermodynamics and kinetics of biochemical reactions. Additionally, various reactor configurations for psychrophilic anaerobic digestion, such as granular sludge and biofilm-based reactors, anaerobic membrane bioreactors, multi-stage anaerobic reactors, direct interspecies electron transfer-assisted reactors, and bioelectrochemical system-assisted reactors, were evaluated and compared. Particular emphasis was placed on the design principles and configurations of these reactors. This review aimed to bridge the gap between reactor design strategies and their underlying mechanisms, offering valuable insights to guide and optimize psychrophilic anaerobic digestion in the future.