Biodiesel synthesis from transesterified Madhuca indica oil by waste egg shell–derived heterogeneous catalyst: parametric optimization by Taguchi approach

The present study investigates the synthesis of biodiesel from Madhuca indica oil (MIO) employing waste egg shell–derived heterogeneous catalyst. The catalyst, developed by calcination of waste egg shells and successive impregnation of sodium using sodium nitrate, was employed to catalyse transesterification of waste Madhuca indica seeds–derived non-edible oil. The productivity of biodiesel in terms of yield was optimized to attain maximum conversion employing Taguchi approach. Initially, parameters affecting the yield were identified statistically and optimized condition for each significant parameter was derived using 3FI model. Among the selected parameters, yield was mainly affected by Methanol to oil ratio (M/O), reaction temperature, and the sodium nitrate concentration kept at the time of impregnation (MCI). The selected optimization technique revealed its accuracy in prediction of maximum biodiesel yield of 81.56% at M/O 9:1, MCI 5%, and temperature 60 °C. The predicted optimized conditions were validated by confirmatory experiments. The produced biodiesel was also characterized by following ASTM standards. Thus, overall results have proved that the waste egg shell–derived catalyst is reusable and bears appreciable catalytic activity for catalysing the transesterification of poor-quality MIO. Hence, it could be said that the proposed study would be beneficial in converting waste into active solid catalyst and renewable fuel.