Green Circular Valorization of Organic Waste through Hydrothermal Treatment and Anaerobic Digestion Coupling

The diversified utilization of biomass energy has gained substantial attention in recent years. Among various technologies, hydrothermal treatment (HTT) is highly effective for processing organic solid waste with high moisture content and low biodegradability while facilitating the fixation of organic carbon. However, HTT produces hydrothermal wastewater (HTWW) as a by-product, which differs from conventional wastewater due to its high concentrations of phenols, ketones, pyridines, and other refractory compounds that are challenging to degrade. Addressing this issue is critical for advancing sustainable waste management.

To achieve dual resource and energy recovery in organic solid waste treatment, we propose integrating HTT with anaerobic digestion (AD) to enable comprehensive waste processing. This study systematically investigated the characteristics of HTWW under varying raw material types and hydrothermal conditions. The results revealed that higher hydrothermal temperatures and longer residence times generate more refractory compounds, which adversely affect the efficiency of subsequent anaerobic digestion.

To enhance the performance of coupled AD technology, we evaluated four strategies: optimization of process conditions, separation of refractory compounds, hydrochar enhancement, and coagulation-adsorption pretreatment. Each approach demonstrated potential in improving anaerobic digestion efficiency to varying degrees. This work provides a theoretical framework for optimizing HTWW treatment through AD and offers practical insights for enhancing biomass conversion efficiency.