A Review on Sewage Sludge Valorization via Hydrothermal Carbonization and Applications for Circular Economy

In pursuit of establishing a circular economy, a waste-to-energy approach is gaining increasing attention. Valorization of sewage sludge constitutes a critical importance due to generation in high quantities, difficulties in disposal, and associating environmental impacts. Hydrothermal carbonization (HTC) is a relatively recent yet an acclaimed method for sewage sludge management and valorization due to process compliance with sludge characteristics. In this review, research studies are evaluated via categorization of application fields of sludge-derived HTC products such as solid fuel production, gas production, soil remediation, nutrient recovery, water treatment, and energy storage. Research findings are compiled and a network mapping is employed for the visualization of the current situation and correlation in respective fields. The potential of HTC for sewage sludge valorization and future projections concerning available techniques are assessed within the context of circular economy. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.