This paper focuses on the preparation and characterization of CaO, MgO and ZnO, both bulk and supported on gamma-Al2O3 and their catalytic activity in the transesterification of soybean oil and castor oil with methanol and butanol in order to produce biodiesel. XRD, SEM, CO2-adsorption followed by TGA and N-2 adsorption have been employed to characterize the prepared catalysts. In supported catalysts, the presence of c-Al2O3 improves alcohol dissociation on the superficial basic sites. The first step of the reaction mechanism is then favored (hydrogen abstraction). In the transesterification of castor oil with butanol, MgO/gamma-Al2O3 and ZnO/gamma-Al2O3 catalysts showed high yields to FABE (Fatty Acid Butyl Ester) (97% and 85%, respectively). These last catalysts constitute an efficient alternative for obtaining second-generation biodiesel, taking into account that castor oil is a nonedible source and butanol is an alcohol that can be obtained from biomass. (C) 2018 Elsevier Ltd. All rights reserved.