A substantial share of the world’s total energy production comes from fossil fuels. In addition to the declining availability of fossil fuel resources, the use of diesel fuel poses numerous environmental threats. Therefore, identifying diverse, renewable, and clean energy sources is essential to ensure the continued advancement of human society. In this study, the effect of four factors, including the molar ratio of alcohol to oil, the weight percentage of catalyst, temperature, and reaction time on the percentage of methyl ester conversion and biodiesel production yield from borage oil seed was investigated at three levels. Design Expert software, Response Surface Methodology (RSM), and Central Composite Design (CCD) were used for statistical analysis and process optimization. The highest desirable process yield was obtained under optimal conditions for biodiesel production, with a molar ratio of 1:8, a weight percentage of catalyst of 0.5, a reaction temperature of 60 °C, and a reaction time of 90 minutes. The biodiesel produced from borage oil through transesterification reaction had satisfactory results in terms of various parameters, including methyl ester content (99.94%), kinematic viscosity at 40 °C (4.1 cSt), density (0.8884 g/ml), flash point (163 °C), pour point (-3 °C), cloud point (-1.3 °C), acid number (0.08 mg KOH/g), and freezing point (-13 °C), in accordance with ASTM 6751-08 and EN 14214-08 standards.
