Biodiesel production from vegetable oil refinery waste using ohmic-assisted esterification

Abstract

The ohmic-assisted esterification method was compared and contrasted with the conventional esterification method for biodiesel (fatty acid methyl esters) production from vegetable oil refinery waste containing high free fatty acids. The reaction variables were free fatty acid:methanol molar ratio (1:1, 1:5, 1:10, and 1:15), catalyst concentration (1%, 2%, and 3%) and reaction time (5, 30, and 60 min). By increasing the conversion yield of free fatty acids to fatty acid methyl esters, density increased while viscosity and refractive index decreased. Optimum reaction conditions were a molar ratio of 1:10 and a catalyst concentration of 3% after 60 min of esterification reaction, while having a 95.74% conversion yield. There was no significant difference between fatty acid methyl esters produced with ohmic-assisted esterification and conventional esterification methods in terms of fatty acid profile, physicochemical and heating properties. Meanwhile, energy consumption by the conventional esterification method was about 25% higher than that of ohmic-assisted esterification. In fact, ohmic-assisted esterification can be considered as a green, cost-effective alternative method for the production of biodiesel from vegetable oil refinery waste.