Structure-property-combustion performance of starch-bound briquettes from hydrothermally pretreated pineapple leaves

Pineapple leaf biomass is an abundant lignocellulosic residue whose direct use as a solid fuel is constrained by low bulk density and weak cohesion. This study evaluated briquettes produced from hydrothermally pretreated pineapple leaves using corn, sago, rice, potato, or tapioca starch. An initial density-based screen compared nominal binder loadings of 20-40%, after which one candidate from each starch group was selected for replicated validation. Since selected candidates differed in both starch source and loading, validation results were interpreted as formulation-specific comparisons rather than isolated botanical-starch effects. Mechanical properties, proximate composition, higher heating value (HHV), comparative stove combustion, FTIR, SEM, and TG/DTG curves were evaluated. CS-40 showed the highest compressive strength (1.65 MPa), low ash content (7.60%), an HHV of 19.87 MJ kg −1 , the lowest burning rate (0.253 g min −1 ), longest combustion duration (162 min), and shortest time to boil 0.5 L of water (12 min). PS-30 recorded the lowest ash content (7.40%), highest HHV (19.94 MJ kg −1 ), and greatest thermal resistance among the starch-bound samples, as indicated by the TG/DTG curves. FTIR and SEM observations were consistent with non-covalent starch-lignocellulose interactions and formulation-dependent matrix consolidation. TG/DTG curves and stove responses showed that intrinsic thermal behaviour did not predict the combustion performance of intact briquettes. Among the density-selected candidates, CS-40 provided the most balanced mechanical, fuel, and combustion performance. These findings support starch-assisted densification of hydrothermally pretreated pineapple leaves for solid-biofuel production. Further work should include untreated controls, solid-recovery measurements, controlled compaction, thermal-efficiency testing, and emissions assessment before scale-up.