Synthesis of Hydrochars via Wet Torrefaction of Biomass for Sustainable Energy Production: A Life Cycle Assessment Study

Abstract

Wet torrefaction of biomass is an emerging technology for synthesizing hydrochars, which could be used as a replacement for conventional coal for energy generation. This study employs a “cradle-to-gate” approach to evaluate the environmental impacts of hydrochar synthesis via wet torrefaction in comparison to conventional fossil-based coal, focusing on an energy value of 10 MJ. The results indicate that the hydrochar synthesis process has a higher overall environmental impact than conventional coal, primarily due to the significant energy demands of wet torrefaction. However, the combustion of hydrochars yields a substantially lower environmental impact, achieving a climate change reduction of ∼93.70% compared to conventional coal, irrespective of whether levulinic acid was used as a catalyst. The environmental impact increases slightly with the addition of levulinic acid due to the resources required to produce levulinic acid. The benefits during combustion remain significant. A sensitivity analysis was conducted by replacing the energy source for wet torrefaction with renewable hydropower to assess the process sustainability further. This substitution resulted in remarkable reductions in climate change potential (global warming) and fossil fuel depletion, with decreases of 98.63% and 99.39%, respectively. Overall, these findings underscore the potential of hydrochars as an environmentally friendly replacement for conventional coal in energy generation, particularly when produced by using renewable energy sources.