Publication date: August 2017Source:Renewable Energy, Volume 109 Author(s): Chaudhry Haider Ali, Abdul Sattar Qureshi, Serge Maurice Mbadinga, Jin-Feng Liu, Shi-Zhong Yang, Bo-Zhong Mu Increasing energy demands, decreasing fossil fuel resources, instability of crude oil prices and pollution problems have compelled to switch over bio-based fuel for transportation, for example, biodiesel. In present study, waste cooking oil (WCO) was evaluated as feedstock for biodiesel production using free lipase in liquid. The response surface methodology (RSM) was used to optimize the interaction between four factors: the reaction temperature, methanol-oil molar ratio, dosage of lipase as biocatalyst and rotational speed. Using this method, the model predicted the optimal conditions reaching up to 86% FAME yield with temperature 44.2 °C, methanol-oil molar ratio (3.05:1), amount of lipase 0.782 g and rotation speed of 170 rpm with incubation period of 24 h. The reactions carried out under optimized conditions confirmed the validity of the model. The use of WCO in lipase catalyzed process can diminish the cost of biodiesel production and will allow lowering the direct use of edible oils to produce biodiesel instead. Thus, present study shows great practical potential to replace fossil fuel with renewable fuel (biodiesel).