Physicochemical Pretreatment on Lesser-Known Shrub Biomass for Bio-Pellet Production

<ns5:p> Abstract* Rising demand for sustainable energy has renewed interest in forest biomass, yet shrubs remain underutilized as their wood has lower strength, durability, and dimensions, relegating it to low-value uses like firewood. Nonetheless, shrubs grow rapidly, are easy to cultivate, and show high ecological adaptability, making them promising bioenergy feedstocks where woody biomass is limited or unevenly distributed. This study aimed to generate a comprehensive dataset evaluating whether physicochemical pretreatment (solvent-based extraction followed by torrefaction) can improve key fuel properties of bio-pellet feedstock from four lesser-known shrub species ( <ns5:italic>Lagerstroemia speciosa</ns5:italic> , <ns5:italic>Ganophyllum falcatum</ns5:italic> , <ns5:italic>Myrsine avenis</ns5:italic> , and <ns5:italic>Mischocarpus sundaicus</ns5:italic> ), with particular emphasis on reducing volatile matter that commonly remains high even after torrefaction and can prevent compliance with Indonesian quality standards. Branch particles (20–40 mesh; 0.41–0.82 mm) collected in South Sulawesi, Indonesia, were extracted at a 1:7 solid-to-liquid ratio using distilled water, ethanol, hexane, or sequential ethanol+hexane at 25 °C (6 h; or 3 h + 3 h sequential) and 50 °C (2 h; or 1 h + 1 h sequential), washed until no solvent odor remained, oven-dried (100 °C, 24 h), and torrefied uniformly at 200 °C for 10 min. Moisture content, weight loss (after extraction and after torrefaction), total weight loss, yield, volatile matter, and gross calorific value were determined and summarized as means with standard deviations (for moisture and volatile matter) across all species–solvent–temperature combinations. The dataset indicates that solvent extraction coupled with torrefaction can reduce volatile matter for the most shrubs species, but values remain relatively high and do not yet meet SNI 8675:2018 thresholds for <ns5:italic>M. avenis</ns5:italic> , underscoring the need for further optimization. Despite limitations in extraction conditions, torrefaction settings, solvent-removal verification, and replicates, the dataset provides evidence to guide process optimization and supports broader utilization of shrub biomass for renewable energy applications. </ns5:p>