Background and Aims: Today, biodiesel is being produced and consumed worldwide as one of the main sources for replacing fossil fuels. The purpose of this study was to investigate the production of biodiesel from restaurants waste frying-oil using commercial calcium oxide as a heterogeneous catalyst. Material and Methods: In this experimental study, commercial calcium oxide was activated by calcination at 750 °C for 5 hours in an electric furnace with a temperature rate of 10 °C /min. Operational parameters for the production of biodiesel in the presence of calcium oxide included weight percent of catalyst, molar ratio of methanol to oil, and reaction time, all were investigated at three levels. Also, the study was carried out ethically and there was no bias and confinement on the part of the researcher during the research process. Results: Optimum conditions for the production of biodiesel in the presence of calcium oxide were obtained as the molar ratio of methanol to oil 12:1, the reaction time of 3 hours and the weight percent of catalyst 2 at 62 °C. Under obtained optimum conditions, the maximum production efficiency of biodiesel from waste frying oil of the restaurant was 95.5±1.22%. Conclusion: The use of commercial calcium oxide showed a great efficiency in the production of biodiesel from waste frying oil of restaurants. Calcium oxide thus is considered to be a very effective catalyst in biodiesel production. Keywords: Biofuel, Calcium Oxide, Waste frying oil, Reusabilit
