Abstract

The pursuit of sustainable energy solutions has intensified interest in biomass valorization, particularly utilizing agricultural residues. This study investigates the production of high-quality bio-briquettes from hydrochar derived via hydrothermal liquefaction (HTL) of locust bean (Parkia biglobosa) pulp, employing cassava starch as a biodegradable binder. Process optimization was performed using the Taguchi L16 orthogonal array, examining binder concentration (20–50%), particle size (300–600 µm), and compaction pressure (4–16 bar), with moisture content as the primary response variable. Analysis of variance (ANOVA) identified binder concentration as the most significant factor (91.64% contribution), followed by compaction pressure (6.11%) and particle size (1.74%). The optimal conditions—20% binder, 300 µm particle size, and 8 bar pressure—produced briquettes with moisture content of 1.09%, density of 0.52 g/cm³, compressive strength of 1.82 kN, calorific value of 18.20 MJ/kg, and reduced ash content of 8.71%. Comparative analysis showed that the optimized briquettes exhibited superior ignition potential, mechanical durability, and combustion efficiency, meeting the standards for household and small-scale industrial fuel applications. The findings demonstrate the viability of converting HTL residues from locust bean pulp into sustainable solid bio-fuels, contributing to waste valorization, renewable energy generation, and rural energy solutions.