Therefore, in order to decrease the environmental impacts related to methanol usage and to reduce the final cost of the product, the optimum molar ratio of oil to methanol was chosen as 1:6. According to these results, the optimal conditions for transesterification reac- tion of fresh soybean oil at room temperature using egg shells as catalyst are the following: 1:6 M ratio of oil to methanol, catalyst amount of 5.8% w/w, and reaction time of 9 h.