In this study, acorn kernel oil with high free fatty acid content is used as feedstock to produce biodiesel. Two stages are used to produce biodiesel after obtaining the acorn kernel oil. The 3.38% free fatty acid content is decreased to 0.14% in the first stage, whereas the acid ester biodiesel is produced using alkaline transesterification reaction in the second stage. The biodiesel production process parameters are the alcohol:oil molar ratio, catalyst concentration, reaction temperature and reaction time. Taguchi experimental design is used for acorn kernel oil methyl ester production via process parameter optimisation. The optimal process parameters are determined to be a catalyst concentration of 0.7 wt%, an 8:1 alcohol:oil molar ratio, a 50 degrees C reaction temperature and 40 min of reaction time using a KOH catalyst in experimental studies. According to the Taguchi method, the most efficient process parameter in acorn kernel oil methyl ester production. Finally, the acorn kernel oil methyl ester yield is 90% under the optimal process parameters obtained by the Taguchi method. (C) 2012 Elsevier Ltd. All rights reserved.