Biodiesel production from non-edible mixed oils: a sustainable approach using jatropha, karanja and waste cooking oil

The world is shifting to greener alternatives such as biofuels due to larger carbon footprints and achieving sustainable goals. Biodiesel made from mixed oils by the transesterification process has tremendous prospects as an alternative fuel source. The quality and efficiency of biodiesel depend on the composition of the mixed oil. This paper focuses on optimizing the mixed oil ratio of the feedstock comprising waste cooking oil (WCO), jatropha oil (J) and karanja oil (K). The attributes of the manufactured biodiesel samples were examined against ASTM D6751 to determine its acceptability as a diesel alternative. Raw oils with free fatty acids (FFA) content exceeding 1% were pre-treated using the esterification method. After esterification, the FFA percentages of jatropha, karanja and waste cooking oil were reduced to 0.832, 1.75 and 0.467%, respectively. Transesterification is carried out at a temperature of 70°C by taking 1% (w/w) KOH as the catalyst for 2 h. Oil to methanol molar ratio was kept at 1:8. The biodiesel yield of the selected mixed oil ratios was approximately 91, 92 and 93%, respectively. These yields align closely with ASTM standards, highlighting the study’s effectiveness and significance. The ratio having a higher amount of jatropha (60:20:20) gave better results in terms of lower FFA content (0.07%), acid value (0.14%), cloud point (− 1°C), pour point (− 4°C), higher flash point (255°C) and fire point (260°C). In this case, the ratio with lower jatropha in it (20:60:20 J:K: WCO) showed better energy content due to its lower flash point (168°C) and fire point (175°C). This biodiesel production process generates minimal waste (primarily from the biodiesel washing stage) with the byproduct glycerin repurposed to make bioplastics and soap. Looking ahead, key directions in this study include developing ways for producing biodiesel from mixed oils utilizing effective catalysts in transesterification, presenting it as a sustainable alternative fuel to diesel.