Upgrading of Corn Stalk Residue and Tannery Waste into Sustainable Solid Biofuel via Conventional Hydrothermal Carbonization and Co-Hydrothermal Carbonization

Abstract

Hydrothermal carbonization (HTC) and co-hydrothermal carbonization (Co-HTC) are efficient thermochemical conversion processes for upgrading the fuel properties of biomass feedstocks. This study investigates the conversion of high moisture industrial waste, leather waste (LW), and agricultural residue, corn stalk (CS) into sustainable solid fuel via the HTC and Co-HTC. The impact of experimental variables, such as HTC temperature, residence time, and reaction pathway (i.e., HTC and Co-HTC process), on the physicochemical properties and fuel quality of hydrochar was also comprehensively explored. The highest heating value of hydrochar product, approximately 23.4 MJ/kg, was obtained from the Co-HTC condition of 280°C for 8 h. The mutual interaction between two biowastes exhibited superior synergistic fuel characteristics, including lower ash content, higher carbon percentage, and improved energy density. However, the remaining ash content of hydrochar decreased by approximately 25.01%-44.52%, produced from both HTC and Co-HTC processes. The hydrothermal treatment process improved the hygroscopic properties of hydrochar. Finding results show that the HTC and Co-HTC are the potential thermochemical conversions for producing sustainable solid fuel from several biowastes. In addition, the Co-HTC process showed a better hydrochar fuel quality.