Optimization of biodiesel production from Sterculia foetida seed oil: Leveraging non-edible crops for sustainable alternative fuel

This research delineates an enhanced methodology for the synthesis of biodiesel from Sterculia foetida (wild almond) seed oil, which is characterized as a non-consumable and underexploited biomass feedstock, utilizing isopropanol as a substitute alcohol in place of methanol. The optimization of the production process was executed employing Response Surface Methodology (RSM) with a Box-Behnken design, aimed at assessing the impact of various parameters including molar ratio (4:1–8:1), catalyst concentration (0.5–1.5 % w /w NaOH), reaction temperature (40–60 °C), and reaction duration (30–120 min) on the yield of biodiesel. The optimal conditions for transesterification—comprising a 6:1 M ratio, 1 % NaOH catalyst, a temperature of 50 °C, and a duration of 60 min—yielded a maximum biodiesel output of 89.2 %. The biodiesel produced demonstrated advantageous fuel characteristics: density (880 kg/m 3 ), viscosity (4.8 cSt), flash point (140 °C), cetane number (54), acid value (0.3 mg KOH/g), and calorific value of 38.7 MJ/kg, which comply with ASTM D6751 specifications. This investigation underscores the enhanced miscibility and phase separation advantages of isopropanol relative to conventional methanol, culminating in superior biodiesel purity and yield. The utilization of non-edible Sterculia foetida oil in conjunction with isopropanol provides a technically feasible and ecologically sustainable avenue for biodiesel production, thereby bolstering renewable energy initiatives while alleviating food-versus-fuel dilemmas.