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 based on the principles of green chemistry, focusing on resource efficiency and waste minimization through reutilization routes involving 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 hydroponic systems. Advanced valorization pathways, including bio-based polymer synthesis, biochar production and 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, were also explored for their potential to enhance resource utilization. Thus, by integrating digestate valorization within a circular bioeconomy framework and industrial symbiosis, this study underscores its role in reducing the environmental impact, improving the carbon footprint and contributing to net-zero emissions. Our discussion further highlights the challenges in digestate processing, regulatory considerations and future research directions to optimize sustainable valorization strategies by integrating green chemistry principles.