Torrefaction of Agricultural Residues for Production of Upgraded Solid Biofuel with Reduced Moisture Content

Abstract

Agricultural residues represent an abundant renewable biomass resource with significant potential for sustainable bioenergy production; however, their high moisture content, low energy density, and poor storage stability limit their direct utilization as solid fuels. The present study investigates the torrefaction of agricultural residues for the production of upgraded solid biofuel with reduced moisture content and enhanced fuel properties under controlled thermal processing conditions. The research focuses on evaluating the influence of torrefaction temperature, residence time, heating rate, and biomass composition on mass yield, energy densification, hydrophobicity, and fuel quality characteristics. Experimental analysis demonstrates that torrefaction effectively modifies the physicochemical structure of agricultural biomass through partial thermal decomposition of hemicellulose and volatile organic compounds, resulting in improved calorific value and reduced equilibrium moisture absorption. Results indicate that optimized torrefaction conditions significantly enhance energy density, grindability, and combustion behavior while minimizing excessive biomass degradation and energy loss. The study further reveals that torrefied biomass exhibits improved storage stability and reduced biological degradation due to increased hydrophobicity and lower oxygen-to-carbon ratio. Comparative assessment with untreated agricultural residues confirms the advantages of torrefaction, including improved fuel handling, higher thermal efficiency, and compatibility with existing solid fuel combustion systems. In addition, the process supports sustainable waste valorization and reduced dependence on fossil fuels for industrial and domestic energy applications.