Hydrothermal carbonization coupled with anaerobic digestion for the valorization of the organic fraction of municipal solid waste.

Hydrothermal carbonization (HTC) was evaluated as a promising treatment to enhance the biomethane potential during anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW). The OFMSW was carbonized at different conditions and HTC products were tested for biomethane potential into AD. Results proved that the use of HTC liquid and slurry into AD led to an increase in biomethane production up to 37% and 363%, respectively, compared to OFMSW. Methane production increased as the HTC process severity decreased, reaching its maximum at 180 °C, 1 h for both HTC products. Energy assessment demonstrated that the combustion of biogas produced by AD of HTC liquid and slurries covers up to 30% and 104% of the HTC thermal demand, respectively. When the energy from hydrochar and biogas combustion was recovered, the process efficiency reached 60%. Hence, HTC coupled with AD demonstrates to be an efficient way to valorize OFMSW.