Abstract In this paper, modified zirconias (WZ, SZ, and TiZ) have been extensively compared under the same reaction conditions as catalysts for both the transesterification of triglycerides (TGs) and the esterification of carboxylic acids (free fatty acids, FFAs) with ethanol. In addition, for the first time, the catalyzed rate of hydrolysis/esterification + transesterification of triglyceride…