Optimization and kinetic studies for biodiesel production from dairy waste scum oil via microwave assisted transesterification

Abstract

This study presents an investigation of the optimization and kinetic aspects of the microwave (MW) heating transesterification process for converting dairy waste scum oil (DWSO) into biodiesel using lithium impregnated calcium oxide from eggshell (Li-ECaO) as a catalyst. The transesterification was done via microwave heating while varying catalyst loading (1 – 5 wt%), methanol to oil molar ratio (6 – 18:1), temperature (55 – 75⁰C), and reaction time in the range of 5 – 25 min. Response Surface Methodology (RSM) optimized the process parameters, yielding an impressive 90.5% biodiesel yield. The optimal operating conditions were determined 3 wt% catalyst loading, 18:1 methanol to oil molar ratio, a reaction temperature of 65ºC, and a reaction time of 25 minutes. A thorough kinetic analysis of the transesterification reaction for the MW heating transesterification of DWSO by Li-ECaO was performed at various temperatures (45 – 75ºC). The pseudo-first order kinetic study of the reaction revealed a moderately low activation energy of 38.86 kJ/mol and a high pre-exponential factor of 1141.27 s−1, which is consistent with previous studies. Importantly, the observed activation energy was lower than that of conventional methods, highlighting the potential of MW heating as a viable technique for future biodiesel production, and using wastes such as DWSO and eggshell could contribute to being greener and environmentally friendly.