This study investigates the characterization and performance of biomass briquettes produced from the branches of the kesambi tree (Schleichera oleosa), a previously underutilized biomass resource in East Nusa Tenggara, Indonesia. The increasing demand for kesambi wood in traditional sei meat smoking has raised concerns about the sustainability of tree resources, highlighting the need for alternative fuel solutions. Utilizing kesambi branches as briquette material could alleviate pressure on tree trunks while preserving the unique qualities of sei meat. The research focuses on the effects of particle size on the briquette's physical and thermal properties. Kesambi branches were ground to different particle sizes (20, 40, and 60 mesh) and mixed with a tapioca flour binder. Briquette properties were analyzed through density, compressive strength, moisture content, ash content, volatile matter, and fixed carbon, using ASTM standards. Results indicated that smaller particle sizes resulted in higher density and compressive strength, enhancing combustion efficiency. The study also applied various empirical models to predict the Higher Heating Value (HHV) based on proximate analysis data, evaluated through AIC and BIC for model accuracy. This research demonstrates that kesambi branch briquettes not only provide a sustainable fuel alternative but also contribute to local economic development by creating job opportunities in biomass processing. Ultimately, these innovations support the conservation of kesambi tree resources while promoting environmental sustainability in energy production.