If the existing natural gas pipeline infrastructure were to be used for the transportation of hydrogen, one of the issues would be the separation of the hydrogen from the natural gas. This work describes such a separation using PEM fuel cell technology. Experiments were performed using a single proton exchange membrane (PEM) fuel cell (25 cm(2) active area MEA), fed with pure hydrogen as well as various hydrogen-methane mixtures and hydrogen-argon mixtures, at temperatures from 293 to 343 K, with either platinum or platinum/ruthenium anode electrocatalysts, and at atmospheric pressure. The experimental results show that little energy is consumed in producing pure hydrogen and that the methane is essentially inert at low temperatures and does not cause significant fouling of the anode electrocatalyst. A simple mathematical model of the electrochemical separation process has been developed. Calculated results are in good agreement with the experimental results. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.