The paper presents the development of a parallel Discrete Element Method (DEM) solver for the open source code, Multiphase Flow with Interphase exchange (MFIX) based on the domain decomposition method. The performance of the code was evaluated by simulating a bubbling fluidized bed with 2.5 million particles. The DEM solver shows strong scalability up to 256 processors with an efficiency of 81%. Further, to analyze weak scaling, the static height of the fluidized bed was increased to hold 5 and 10 million particles. The results show that global communication cost increases with problem size while the computational cost remains constant. Further the effects of static bed height on the bubble hydrodynamics and mixing characteristics are analyzed. (C) 2012 Elsevier B.V. All rights reserved.