Mechanical Characteristics of Cashew Nut Shell-Sawdust Composite Briquettes Subjected to Different Drying Techniques

Abstract

The growing demand for sustainable energy has intensified interest in converting agricultural residues into high-quality biofuels. This study investigates the production and mechanical performance of composite briquettes made from cashew nut shells (CNS) and sawdust (SD) subjected to three drying methods: open sun, natural convection solar drying, and forced convection solar drying. CNS and SD were carbonized, milled, sieved into five particle sizes, and combined at varying ratios with cassava starch to produce briquettes under 5?MPa compaction. Moisture content, compressive strength, density, and shatter resistance were evaluated to determine the effect of drying technique and particle size. Results indicated that forced convection drying achieved the lowest moisture content (3.96?%) and the highest mechanical performance, with maximum compressive strength of 0.53?MPa, density of 563?kg/m³, and shatter resistance of 98.77?% observed in briquettes composed of 50% CNS, 50% SD, and 0.2?mm particle size. Smaller particle sizes consistently yielded higher density, compressive strength, and shatter resistance due to improved inter-particle bonding and reduced voids. Regression models developed for compressive strength exhibited strong agreement with experimental data (R² = 0.82–0.96). The study demonstrates that optimized drying methods, particularly forced convection solar drying, coupled with appropriate particle sizing and biomass mixing ratios, significantly enhance the structural integrity and quality of CNS–SD briquettes, providing a sustainable and efficient solid biofuel alternative.