Torrefaction pretreatment of sugarcane bagasse coupled with pelletization for carbonaceous fuel production

Sugarcane bagasse is an abundantly available biomass feedstock which has great potential for biochar carbonaceous fuel production however, the low energy density, high moisture content and low mechanical strength of bagasse and its derived biochar have considerably restricted its economic viability and widespread application. This study proposes a novel approach integrating torrefaction pretreatment of biomass coupled with cold-press pelletization to produce solid carbonaceous fuel with high energy density and mechanical strength. A systematic investigation was conducted to elucidate the regulatory mechanism by which torrefaction temperature governs key fuel properties including char yield, proximate analysis, energy density, higher heating value (HHV), and CO 2 gasification reactivity. Moreover, the influence of binder type on pelletization mechanism and mechanical strength was also thoroughly investigated. Experimental results demonstrate that torrefaction temperature is a critical factor governing char yield, heating value, gasification reactivity, and mechanical strength of the resulting char. As the torrefaction temperature increases from 200 °C to 325 °C, the char yield decreases markedly from 76.42 wt.% to 36.42 wt.%, whereas the heating value rises from 18.31 MJ/kg to 24.52 MJ/kg. In contrast, gasification reactivity exhibits a non-monotonic trend—initially increasing and subsequently decreasing with rising temperature. Further investigation reveals a synergistic interaction between binder dosage and torrefaction temperature on mechanical strength: the maximum compressive strength of 8006.16 N is achieved for briquettes prepared with a 5 wt.% binder addition at a torrefaction temperature of 200 °C. Mechanistic analysis of briquette formation indicates that the binder enhances the mechanical strength of sugarcane bagasse-derived char through combined contributions of mechanical interlocking, particle bridging, and intermolecular interactions with char particles. This work provides a theoretical foundation for producing high performance solid carbonaceous fuels from sugarcane bagasse.