Comparing three options for biodiesel production from waste vegetable oil.

Biodiesel production deserves continued study and optimization of production procedures due to its environmentally beneficial attributes and its renewable nature. From a waste-management standpoint, production of biodiesel from used cooking oil is environmentally beneficial since it provides a cleaner way of disposing of these products than is typically the case. Biodiesel produced by basecatalyzed transesterification of vegetable oil is usually performed in batch reactors where the required energy is provided by heating accompanied by mechanical mixing. Using this technique, the best yield percentage was obtained using a methanol/oil molar ratio of 6:1, potassium hydroxide as the catalyst (1%), and 65°C temperature for one hour. Alternatively, ultrasonication can provide an effective way to attain the required mixing while providing the necessary activation energy. It was concluded that transesterification by low frequency ultrasound (20 kHz) offered a lot of advantages over the conventional classical procedure. It proved to be efficient (biodiesel yield up to 98–99%), as well as time and energy saving (dramatic reduction of reaction time to 5 min, compared to one hour or more using conventional batch reactor systems, and a remarkable reduction in static separation time to 25 min, compared to 8 hours). The third option studied was the application of microwave irradiation. The application of radio frequency microwave energy offered a fast, easy route to this valuable biofuel with advantages of enhancing the reaction rate and improving the separation process. The methodology allowed for the use of high FFA content feedstock, including used cooking oil, hence reducing the cost of production, which constitutes a major hurdle towards widespread commercialization of biodiesel.