A specific methodology was applied to investigate the expected impact on sustainability of processes for hydrogen production by steam reforming of natural gas. Reference process schemes based on the current industrial state-of-the-art and on innovative steam reforming technologies were defined and assessed. The methodology allowed the calculation of a sustainability "fingerprint" of the reference schemes, based on sustainability key performance indicators. The results obtained evidenced the potential advantages of innovative processes, based on integrated conversion and internal membrane separation reactors. However, the valorization of the by-product streams is an essential requirement to reduce the impact on sustainability of these processes. Besides the improvement of the reaction section, the optimization of the overall separation efficiency and of energy requirement emerged as the key elements that control the overall sustainability performance of these processes. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.