Alum has been taken beyond its traditional roles as a water treatment chemical and a confectionary additive to a new role as a catalytic precursor in biodiesel production. Its catalytic potentials were empirically proved via palm oil transesterification with methanol and application of solid state instrumental characterization techniques. The catalyst was very clean, efficient, simple and cheap to produce, and could be clearly separated from the reaction products. When the reaction was carried out under the conditions of catalyst to oil ratio of 7.09 wt%, reaction time of 12 h and temperature of 170 degrees C, methanol to oil molar ratio of 18:1 and catalyst preconditioned at 550 degrees C, the yield of fatty acid methyl ester (FAME) obtained was 92.5 wt%. (C) 2009 Elsevier B.V. All rights reserved.