Thermal dehydrogenation of Ca(BH4)(2) and Ca(BH4)(2)-2MgH(2) composite has been investigated, and the results were compared. The Ca((BH4)(2) dehydrogenated in two steps between 325 degrees C and 500 degrees C as per the reactions Ca(BH4)(2)= CaH2 + 2B + 3H(2), and Ca(BH4)(2) = 1/3CaB(6) + 2/3CaH(2) + 10/3H(2). The partial dehydrogenation of CaH2 also takes place during the second step dehydrogenation according to the reaction CaH2 + 63 = CaB6 + H-2. The completion of second step dehydrogenation requires a temperature of higher than 500 C. The activation energies corresponding to these steps were found to be 149 +/- 8 kj/mol and 162 +/- 10 kJ/mol, respectively. The Ca(BH4)(2)-2MgH(2) composite dehydrogenates in a single step as per the reaction: Ca(BH4)(2) + 3MgH(2) = CaMg2 + 2B + 7H(2) + Mg. The dehydrogenation of Ca(BH4)(2)-2MgH(2) started at 340 degrees C and completed before 450 degrees C. The activation energy of Ca(BH4)(2)-2MgH(2) dehydrogenation was found to be 180 8 kj/mol. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.