A comparative analysis of a conventional industrial process and a membrane reactor plant for hydrogen production via natural gas steam reforming is proposed by calculating two sustainability metrics: mass and energy intensities. The analysis takes into account membrane reactors equipped with hydrogen-selective membranes (Pd-based) which can operate at milder temperatures (500 degrees C) and pressure (1.0 MPa) conditions and at higher CH4 conversion levels (90-100%) than that achieved in conventional industrial systems. The use of the MR retentate stream to produce the steam required as feed for the reforming section is proposed and for this option a reduced mass intensity is calculated (reduced amount of fuel to the process) with respect to the conventional plant. The reduction is in the range 25-32% for the MRs operated at m = 3 and 44-50% for the MRs operated at m = 2. A more important saving concerns the energy use. (C) 2009 Elsevier Ltd. All rights reserved.