Improving biodiesel yield from pre-esterified inedible olive oil using microwave-assisted transesterification method

Abstract

In the present research, biodiesel production from olive oils with different initial free fatty acid concentrations (2.5, 5.0, and 10.0%) was evaluated. A two-stage acid-catalyzed esterification and alkaline-catalyzed transesterification (ACT) process using the microwave heating method was compared with the traditional heating method. Free fatty acid was reduced to less than 2.0% in the first stage. Although no significant difference was observed between microwave and traditional esterification methods in terms of fatty acid reduction, the microwave treatment significantly decreased reaction time by 92.5%. Comparing microwave ACT results with those of the traditional heating method showed that the microwave can significantly increase methyl ester yield and purity, and simultaneously decrease reaction time. Physical constants of methyl esters were also improved using the microwave heating method. Therefore, the microwave heating method can be regarded as an efficient method instead of the two-stage method for biodiesel production. This method is capable of using inedible olive oil with high concentrations of free fatty acids.

Keywords

• Biodiesel
• Esterification
• Microwave
• Olive oil
• Transesterification