Optimization and characterization of biocoal production from giant leucaena wood and sugarcane leaf via dry torrefaction process

Abstract

The efficiency of conventional biomass as a direct solid fuel is often limited by its high moisture content, volatile organic compounds and low heating value. This study optimizes the production of biocoal from giant leucaena wood (GL) and sugarcane leaf (SL) through dry torrefaction using response surface methodology (RSM) and central composite design (CCD). The torrefaction temperature and retention time of the GL were optimized at 275 °C and 9 min, respectively, providing biocoal with higher heating value (HHV) of 24.05 MJ/kg and energy yield of 73.19 %. The optimized conditions for torrefaction of the SL were performed at 225 °C for 30 min, providing biocoal with HHV of 22.47 MJ/kg and energy yield of 76.93 %. The torrefaction process primarily produced torrefied solids, followed by condensates and non-condensable gases, including CO₂, CO and CH₄. The biocoal derived from woody biomass had better combustion efficiency and completeness of combustion than commercial coal (sub-bituminous) and biocoal derived from non-woody biomass.