Effect of Water Temperature, Contact Time and Particle Size on the Leaching Characteristics of Organic and Inorganic Matter from Sugarcane Trash Briquettes

Global depletion of fossil fuels and the environmental costs of their use motivate renewable alternatives. Sugarcane trash is abundant but rich in potassium, silica, chlorine, and alkali/alkaline earth metals, which drive ash formation, slagging, fouling, corrosion, and hazardous air pollutants during combustion. This study evaluates water leaching as a pretreatment to reduce problematic inorganic/organic constituents and to improve combustion and emission performance of sugarcane trash briquettes. Raw cane trash (CO 421, Migori County) was collected, size-reduced (1, 5, 10 mm), and 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). Post-leach solids were densified via hydraulic press (18 MPa; DIN 54385:2016-08). Elemental and ash-forming species (K, Na, Ca, Mg, Si; Cl, S, P) were quantified by standard methods; leachates were analyzed for pH, EC, TOC, and organic acids. Leaching increased C from 46.27 to 49.73 wt% and eliminated detectable Cl; N and S decreased by 39.5% and 66.7%, respectively. Ash-forming K and Mg in solids fell by 63.09%and 44.00%, while Si declined slightly (≈4.3%) and Ca rose (≈15.9%). Leachates were mildly acidic (pH ≈ 5.5) and contained organic acids totaling 2.91% of TOC. Electrical conductivity trends and performance gains were strongest with smaller particle size, higher temperature, and longer contact time. The optimum temperature, time and size were 50 °C, 60-minute and 1 mm, respectively.