Valorization of hydrothermal carbonization products by anaerobic digestion: Inhibitor identification, biomethanization potential and process intensification

Integrating hydrothermal carbonization (HTC) and anaerobic digestion for biorefinery-oriented full utilization of wet organic wastes is a promising emerging technology. The objectives of this study were to identify the potential inhibitory substances, evaluate the biomethane potential of mixed and aqueous products and explore process intensifying strategies. The results indicated that the high HTC temperature of 240 °C resulted in a significantly low methane yield of 60 ± 5 mL/g COD and a high Short chain fatty acid (SCFAs) accumulation of 4174 ± 76 mg/L. GC-MS analysis showed that the contents of inhibitory pyrazines, pyridines and ketones in aqueous fraction at 240 °C substantially increased from 13.14%, 0.4%, 0.55% at 180 °C to 23.34%, 2.89%, 5.13%, respectively. When the aqueous products obtained from 240 °C-HTC was supplemented or pretreated by carbonaceous material, the methane yields were greatly improved and increased to 1.3-fold and 1.8-fold, respectively. These finding could provide some valuable technical information for HTC based biorefinery of organic waste.