Optimisation of biodiesel production from dairy effluent scum using calcined egg shell as a transesterification catalyst

The production of biodiesel from dairy effluent scum using calcined egg shell as the transesterification catalyst has been explored. Eggshell powder was calcined at 900 °C for 3 h and used as catalyst. The influence of methanol-oil molar ratio, catalyst concentration and reaction temperature were studied using Response Surface Methodology employing a Central Composite Rotatable Design. An empirical model that relates the yield of biodiesel to the studied factors was obtained. The model has high statistical significance at 95% confidence interval with R 2 and adjusted R 2 values of 96.31% and 95.75% respectively. Results showed that among the three studied factors, the methanol-oil molar ratio had the greatest contribution to the yield of dairy effluent scum derived biodiesel followed by reaction temperature and finally, the catalyst concentration. Significant interaction effects were also present between methanol-oil ratio and catalyst, catalyst and reaction temperature and methanol-oil ratio and reaction temperature. Accordingly, the optimal variable settings were 14.355:1 methanol-oil molar ratio, 3.09% catalyst loading by weight of pre-treated dairy scum oil and 55.20°C reaction temperature; with a corresponding yield of 92.72%.