Effect of water leaching pretreatment on the physical and combustion properties of sugarcane residues briquettes

Abstract

Biomass briquettes improve handling, storage, and energy density, yet sugar cane residue briquettes suffer from high mineral content that drives ash deposition, slagging, corrosion, and equipment wear. This study evaluates water-leaching pretreatment followed by briquetting with cassava starch binder to reduce problematic inorganics and enhance the physical and combustion properties of sugarcane residue briquettes. Raw sugar cane residue was collected and size-reduced to 1, 5, and 10 mm, then leached in ultrapure water at 25, 50, and 100 °C for 20, 40, and 60 min using a 3 × 3 × 3 full factorial design (27 runs; triplicates). Leached solids were blended with cassava starch binder (20:3, w/w) and densified on a hydraulic press at 18 MPa (Ø 50 mm × 50 mm). Physical and combustion properties were measured according to ASTM/ASABE protocols. Elemental analyses were also performed. ANOVA and regression were used to assess effects of particle size, leach temperature, and time. Leaching and densification measurably upgraded fuel quality: HHV increased from 16.85 to 17.99 MJ kg −1 (+ 6.94%); volatile matter rose from 73.80 to 76.75% (+ 3.80%); ash decreased from 4.14 to 2.77% (− 33.00%); fixed carbon decreased from 22.18 to 14.03% (− 36.75%); mechanical durability improved from 89.50 to 96.52% (+ 7.02%); and bulk density rose from 274 to 304.24 kg m −3 (+ 11.04%). Moisture content declined from 61.7 to 54.51%. Elemental shifts included elimination of detectable Cl, reductions in N (− 39.5%) and S (− 66.7%), and large decreases in ash-forming K (− 75.24%) and Mg (− 44.00%). Leachates were mildly acidic (pH ≈ 5.5) and contained organic acids totaling 2.91% of TOC. Across responses, particle size exerted the strongest effect, with higher temperature and longer time generally intensifying removals and performance gains; the most severe condition (100 °C, 60 min, 1 mm) yielded the best overall properties. Thus, water leaching reduces ash-related risks and heteroatom loads while improving HHV and handling properties supporting conversion of an underutilized residue into a renewable fuel that can displace wood charcoal, curb open burning, and enable local micro-enterprise.