The reactions were carried out in a batch reactor at 65 °C or 150 °C under vigorous stirring. Typical reactions were performed with 25 ml of vegetable oil (100% soybean oil; Xi’an Jiali Grease Industrial Co., Ltd., Xi’an, China) and 9 ml of methanol (methanol/vegetable oil molar ratio 9:1; molecular weight of soybean oil “871 g/mol” was used) using 3 wt% (catalyst/oil weight ratio) of eggshell derived catalyst at 65 °C for the specified time. The reaction products were analysed using the following procedure. The samples were separated from catalyst and glycerol by centrifuge. The glycerol could be separated because it was insoluble in the esters and had a much higher density. Then methanol was removed using a vacuum pump and the obtained product was added to deuterated chloroform for 1H NMR to determine the yield to methyl ester.