A detailed computational fluid dynamics (CFD) model has been developed in this study for the water gas shift of untreated biogas reformate in both fixed bed and membrane reactors to gain insights into the interaction of 3Ni5Cu/Ce0.5Zr0.33Ca0.17 catalyst with fluid transport phenomena taking place in the reactor. The developed CFD model closely agreed with data from both literature and experiments. An average absolute deviation of 8.59% and 6.32% was obtained when the CFD model was validated with a fixed bed reactor and membrane reactor experiments respectively. The membrane reactor enabled equilibrium conversion at 2.95 gcat.h/rnol CO weight-time with equilibrium conversion attained at lower weight-time and steam to carbon ratio of 3.4. Also, it was found that the counter-flow configuration resulted in better enhanced CO conversion, and the wall heat transfer coefficient above 8.6 W/m(2)/K had negligible on conversion, amounting to only a 1% increase in conversion for both reactors. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.