Cleaner production of methyl ester from non-edible feedstock by ultrasonic-assisted cavitation system

Abstract Biodiesel by non-edible oils via ultrasonic cavitational technique offers a unique and novel approach towards waste management. This study aims to synthesis biodiesel from two non-edible sources namely; Salvadora alii oil and Thespesia populneoides oil. Transesterification was carried out in the presence of solid base calcium oxide catalyst while using an ultrasonic cavitation (UC) reactor. Parametric optimisation was conducted by central composite design and response surface methodology. Results revealed that optimum condition to obtain maximum yield (≈92 wt %) of Salvadora alii methyl ester was as; molar ratio = 10:1 (alcohol: oil), catalyst amount = 3 wt %, and amplitude = 50% in 30 min of reaction time. Similarly, optimum condition was found satisfactory to render maximum yield (≈88.6 wt %) of Thespesia populenoides methyl ester as molar ratio = 6:1 (alcohol: oil), catalyst amount = 3.5 wt %, and amplitude = 45% in 30 min of reaction time. At obtained optimised values UC was compared with mechanical stirring (MS). UC showed 3 fold higher reaction constants and 3 fold more time efficiency than MS. The superiority of UC over MS can be established. Biomass waste to biofuel can make biodiesel synthesis towards cleaner fuel. These results suggest that combination of non-edible oils and UC technology have the potential to make cleaner process. Most of the fuel properties were met the EN 14214 and ASTM D 6751 standards.