Integration of hydrothermal carbonization treatment for water and energy recovery from organic fraction of municipal solid waste digestate

Anaerobic digestion is an efficient way of using a wet fraction of municipal solid waste (MSW) for energy purposes as it can produce biogas. The moisture content of the digestate after application of mechanical dewatering is still high, and the amount of heat needed for drying is significant. Hydrothermal carbonization (HTC) is a process that can potentially offer great benefits by improved mechanical dewatering and valorization of the digestate into a better quality solid fuel. This study focuses on the determination of the optimum HTC process conditions to recover water from the MSW digestate. Different process conditions as temperature (180, 200, and 230 degrees C) and residence time (30, 60, and 120 min) were tested. Furthermore, a mass and energy balance was carried out and a process model in Aspen Plus was built. Results showed that HTC treatment increased the water recovery (40-48%) during the dewatering process compared with the original feedstock (18%). The process model showed a positive energy balance of 110 kWh per ton of MSW digestate treated with an electrical efficiency of 23.9%. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Automated summary

Anaerobic digestion is an efficient method for utilizing wet municipal solid waste (MSW) to produce biogas. This study focused on the determination of optimum hydrothermal carbonization (HTC) process conditions to recover water from MSW digestate. Results showed that HTC treatment increased water recovery during the dewatering process compared with the original feedstock. A process model was built, demonstrating a positive energy balance and electrical efficiency.