Optimization of used cooking oil methyl ester production using response surface methodology

Monoalkyl ester of vegetable oil, animal fat, and used cooking oil (UCO) is termed as biodiesel. Biodiesel obtained from UCO is gaining importance as an alternate fuel for usage in diesel engines since its fuel properties are compatible with that of diesel fuel. The percentage of free fatty acid (FFA) in the oil determines the production process of biodiesel. In this work, the FFA value of one-time and multi-time UCO was determined using titration method as 2.20% and 3.20%, respectively. The raw UCO is converted into biodiesel by means of acid esterification or alkali transesterification. It involves the addition of methanol with raw oil in the presence of catalysts such as H2SO4 or NaOH. In the current study, one-time UCO has been selected for which alkali-based transesterification was found to be the most suitable methodology to extract the biodiesel. The transesterification process is governed by reaction parameters such as methanol-oil ratio, reaction temperature, reaction time, and catalyst loading. The optimization of the above parameters was carried out by means of response surface methodology using Box-Behnken design. The response surface plot and contour plot have been plotted among various parameters that influence the biodiesel production. An optimized UCOmethyl ester yield of 92.43% is achieved at 1:8 molar ratio, 0.6 wt% catalyst loading, 80 min reaction time, and 55 degrees C reaction temperature. Based on these parameters, the experimental yield was found to be 91.75% which has been found in accordance with the optimized yield, and this proves that response surface methodology is an effective approach in increasing the yield.