A Life Cycle Assessment of the Combined Utilization of Biomass Waste-Derived Hydrochar as a Carbon Source and Soil Remediation

The conversion of waste biomass to hydrochar by hydrothermal carbonation (HTC) treatment is a promising technology for waste management, and the thorough utilization of hydrochar can reduce the environmental load. Herein, a life cycle assessment (LCA) was performed to evaluate hydrochar as a carbon source in wastewater plants (WWTPs) and subsequently soil remediation. The simulated combined utilization of hydrochar showed that Bacillus subtilis may utilize the dissolved organic matter (DOM) of hydrochar that contains many aliphatic organic substances, and the microbially treated hydrochar retains most of the nutrients for crop growth. LCA shows that hydrochar could avoid 28% of the environmental load of WWTPs in terms of global warming (GWP100) and 47% of the environmental load of freshwater aquatic ecotoxicity and could reduce 54% of the environmental impact of soil fertilization in terms of eutrophication and 34% of GWP100 in soil remediation. Furthermore, LCA results indicate that hydrochar derived at 160 °C has the lowest environmental load in the combined utilization. This study proposes an optimized utilization of biomass wastes and extends the life cycle of derived hydrochar by experimental determination and the LCA method.