Capturing the Signal of Reactive Oxygen Species in Anaerobic Digestion Process and their Downstream Role: A Worthy Endeavor

Anaerobic digestion (AD) offers a promising alternative to fossil fuels and is of great significance for promoting environmental sustainability. However, the compositional complexity of organic waste introduces poorly understood inhibitory effects on the AD process, leading to reduced methane yields and process instability. Reactive oxygen species (ROS), potent oxidants produced under microbial stress, can damage cellular components and disrupt methanogenesis; yet, their roles in AD remain largely unexplored. This review highlights, for the first time, a comprehensive perspective on the formation pathways and fate of key ROS oxidants within anaerobic systems and the need for accurate ROS detection methods. Importantly, we propose a novel insight that ROS may facilitate the degradation of emerging organic pollutants in digestate, offering increased safety before land application for soil remediation. Furthermore, the review provides a pioneering discussion on the link between ROS and CH₄/CO₂ emissions, including mechanistic insights and long-term environmental implications. Our findings suggest that the potential greenhouse gas flux from digestate due to ROS-related processes warrants serious attention. Overall, this review aims to advance the understanding of ROS in anaerobic digestion and support the optimization of both AD performance and its downstream ecological impacts.