Abstract. In this study, the use of liquid-phase plasma discharge (LPPD) technology to accelerate the transesterification process was explored. An innovative LPPD reactor was first evaluated by varying the conductive opening size on the dielectric plate (0.75, 1.0, and 1.25 mm) coupled with five methanol to oil molar ratios (MOMR; 3, 4, 5, 6, and 7) and two liquid flowrates through the reactor (2.7 and 4.1 mL s-1) at a given catalyst (NaOH) to oil ratio (NaOR) of 0.8% (w/w). The optimal combination of opening size (1.0 mm), MOMR (5), and flowrate (2.7 mL s-1) was then fixed while the NaOR was varied from 0.4% to 1.2% (w/w) in 0.2% increments to determine the best NaOR for the reactor. The results showed that the best combination of the four operating parameters was an opening size of 1.0 mm, MOMR of 5, liquid flowrate of 2.7 mL s-1, and NaOR of 0.6% (w/w), with which a biodiesel conversion rate of 99.5% was obtained at an applied voltage of 1.2 kV. The transesterification reaction time was found to be only 923 ms. The developed LPPD technology has potential to position biodiesel competitively against petroleum diesel. Keywords: Biodiesel conversion, Liquid-phase plasma discharge, Soybean oil, Transesterification
