Thermoecological Cost Analysis of Hydrothermal Carbonization for Valorization of Under-Sieve Fraction from Municipal Solid Wastes

Municipal solid waste (MSW) management poses significant challenges due to the generation of organic waste materials, including the under-sieve fraction (USF), which contains high moisture and organic content. Hydrothermal carbonization (HTC) has emerged as a promising technology for converting USF into hydrochar (HC), a valuable energy-rich material with improved combustible properties. Despite the potential of HTC for waste valorization, comprehensive studies on the thermoecological cost (TEC) and environmental implications of applying HTC to USF are limited. In this study, a detailed analysis of the TEC associated with the HTC process applied to USF from MSW was conducted. The TEC assessment was conducted considering varying dilution ratios (DS/W), operational temperatures (180–220 °C), and reaction times (1–8 h) to evaluate the energy efficiency, resource utilization, and environmental impact of the HTC process. Comparative assessments were made with alternative USF treatment methods, such as bio-stabilization, landfilling, and wastewater treatment. The results indicate that the optimal conditions for minimizing TEC are a temperature of 180 °C, a reaction time of 1 h, and a dilution ratio of 0.15, achieving a TEC value of approximately 9.25 GJ per ton of USF. This represents a significant reduction compared to the conventional treatment methods, which showed a TEC of 14.9 GJ/ton of USF. This study provides a comprehensive comparison of HTC with alternative USF treatment methods, such as bio-stabilization and landfilling, highlighting HTC’s superior energy efficiency and environmental sustainability. These findings offer valuable insights into the energy consumption, resource utilization, and environmental impact of HTC, emphasizing its potential for sustainable waste valorization.