Anaerobic Digestion-derived Digestate Valorization: Green Chemistry Innovations for Resource Recovery and Reutilization

Abstract

Anaerobic digestion (AD) plays a crucial role in sustainable waste management, converting biowaste into biogas while generating digestate as a nutrient-rich by-product. This review explores innovative digestate valorization strategies through the principles of green chemistry, focusing on resource efficiency, waste minimization through reutilization routes of environmentally benign processes. The study examines the physicochemical characteristics of digestate and highlights its applications in sustainable agriculture, bioprocessing for enzyme production, algal biorefineries and application in hydroponic systems. Advanced valorization pathways, including bio-based polymer synthesis, biochar production and the recovery of high-value chemicals such as volatile fatty acids, lactic acid and humic substances for commercial viability are critically analyzed through technoeconomic feasibility and life cycle assessment insights. Inorganic nutrient recovery techniques, including ammonia stripping, struvite precipitation and membrane separation, are also explored for their potential to enhance circular resource utilization. By integrating digestate valorization within a circular bioeconomy framework and industrial symbiosis, this study underscores its role in reducing environmental impact, improving carbon footprint and contribution to net-zero emissions. The discussion further highlights challenges in digestate processing, regulatory considerations and future research directions to optimize sustainable valorization strategies by integrating green chemistry principles.