The traditional method of biodiesel production is based on the transesterification of triglycerides using an alkaline catalyst dissolved in methanol. The aim of this study was to replace a homogeneous alkaline catalyst with a heterogeneous catalyst on the carbon support. The use of a carbon enables the catalyst to be reusable in the production process, eliminates the formation of soaps and increases the glycerol purity. Fatty acid methyl esters were obtained from the transesterification of corn oil using KOH supported on activated carbon (KOH/AC). The effect of the molar ratio of methanol to oil, reaction time and catalyst amount were used to optimize the transesterification reaction. The optimum condition for waste corn oil transesterification to methyl ester was obtained below 0.75 wt.% catalyst amount. The yield was up to 92 wt.% at 62.5 degrees C, 1 h reaction time and 3:1 methanol-to-oil ratio. This study demonstrated that the transesterification of the waste corn oil using methanol can be effectively catalyzed by the developed catalyst. (C) 2018 Elsevier Ltd. All rights reserved.