Optimizing biodiesel production: Energy efficiency and kinetic performance of microwave and ultrasonic transesterification vs. conventional techniques

This study explores the enhancement of biodiesel production via microwave- and ultrasonic-assisted transesterification, comparing their efficiencies against conventional methods using potassium carbonate (K₂CO₃) as a cost-effective heterogeneous catalyst. The results show that conventional transesterification, under optimal conditions (60 min, 12:1 methanol-to-oil (MTO) molar ratio, 2.5 wt% catalysts at 60 °C and 300 rpm), yields 90.7 % biodiesel while consuming 2574 kJ of energy. In contrast, microwave-assisted transesterification (6:1 MTO molar ratio, 1 wt% catalyst, 1 min) and ultrasonic-assisted transesterification (6:1 MTO molar ratio, 1 wt% catalyst, 15 min) achieved 90.7 % and 90.3 % biodiesel yields, respectively, while reducing energy consumption by 97.5 % and 85 %. The results prove that the microwave is the most effective technique for biodiesel production with minimum operating conditions, energy consumption, and the highest biodiesel specifications followed by the ultrasonic technique. Blending the produced biodiesel with petrodiesel reduced the CO exhaust emission from 0.18 to 0.11 vol % and HC exhaust emission from 47 to 32 ppm. This study affords a simple, cheap, available process that can be implemented to promote and facilitate the widespread production and adoption of biodiesel as a renewable energy source. •Ultrasonic technology slashes energy use by 85 % in biodiesel production compared to conventional method.•Ultrasonic technology uses 25 % less methanol and 60 % less catalyst needed.•Microwave technology boosts efficiency with a 97.5 % reduction in energy compared to conventional method.•Microwave technology halves methanol use and reduces catalyst by 60 %.