Reducing the energy requirement is the primary challenge for post-combustion CO2 capture technologies. Growing interest is being shown in membrane processes as an alternative to the reference technologies (such as gas-liquid absorption in amine absorption). However, these membrane processes remain energy intensive when the recommended CO2 purity and capture ratio (both typically at 90%) are imposed. In this study, a systematic parametric analysis of the energy requirement of a single stage membrane gas separation module has been performed. Different inlet CO2 contents and membrane selectivity performances have been compared. In contrast to previous studies, the capture ratio and CO2 purity constraints have been relaxed below the 90% target in order to possibly identify the most appropriate role and place of membrane processes in a Carbon Capture and Storage (CCS) framework. It is shown that diluted CO2 feed streams (such as natural gas turbine flue gases) systematically require excessive energy for CO2 capture. However, single stage membrane units offer interesting possibilities with a very low energy requirement when used as a pre-concentration step for a moderate inlet CO2 content (15-30%) or as a final step for concentrated streams (50% inlet CO2 content or more). Finally, guidelines for improved integration strategies of membrane units in different carbon capture scenarios, with a particular emphasis on hybrid processes, are proposed. (C) 2012 Elsevier B.V. All rights reserved.