River snail shells-derived CaO was used as a heterogeneous catalyst to synthesize biodiesel via transesterification of palm oil with methanol. The shell materials were calcined in air at 600-1000 degrees C for 3 h. Physicochemical properties of the resulting catalysts were characterized by TGA-DTG, XRD, SEM, BET, XRF, FT-IR and TPD. CaO catalyzed transesterification mechanism of palm oil into biodiesel was verified. The effects of adding a co-solvent on kinetic of the reaction and %FAME yield were investigated. %FAME yield of 98.5% +/- 1.5 was achieved under the optimal conditions of catalyst/oil ratio of 5 wt.%; methanol/oil molar ratio of 12: 1; reaction temperature of 65 degrees C; 10% v/v of THF in methanol and reaction time of 90 min. The results ascertained that river snail shells is a novel raw material for preparation of CaO catalyst and the co-solvent method successfully decreases the reaction time and biodiesel production cost. (C) 2016 Elsevier Ltd. All rights reserved.