The kinetics of the CaDG catalysed transesterification of WCO were studied at different operating temperatures ranging from 45 °C to 60 °C and corresponding graph between X/(1 − X) vs. t is shown in Fig. 6. The obtained reaction rate constant from these plots were 0.029, 0.034, 0.095 and 0.198 (L mol−1 min−1) for temperature 45, 50, 55 and 60 °C respectively. It was observed that reaction rate constant (k) increased from 0.029 to 0.198 (L mol−1 min−1) as temperature increased from 45 °C to 60 °C. The activation T-5224 was determined from a plot of ln(k) vs. (1/T) shown in Fig. 7 and the activation energy was found to be 119.23 kJ/mole. Salamatinia et al.  studied the kinetics of transesterification of vegetable oil in the presence of heterogeneous catalyst SrO using low frequency ultrasonic irradiation (20 kHz, 200 W) and investigated that activation energies varied between 70.63 kJ/mole and 136.93 kJ/mole. Choudhury et al.  reported the activation energy of 133.5 kJ/mole for ultrasound assisted transesterification of crude Jatropha curcas oil with methanol in the presence of heterogeneous catalyst CaO. Due to the three phase heterogeneity of the reaction system, limitations in the mass transfer results in a higher activation energy. Another possible reason for the high activation energy might be due to the impure nature of the oil which hindered the activity of the catalyst by adsorbing on it .