The efficient use of primary energy sources, which can be used for hydrogen production, is addressed by a consideration of four key measures, which reflect the ability of different sources and processing routes to meet underlying needs and the practical demands of energy on a large scale. The measures considered are carbon dioxide emission reduction, primary energy availability, land use implications and hydrogen production costs. Fourteen pathways to hydrogen are considered involving fossil fuels and nuclear energy as well as the range of renewable sources, and including additional strategies for carbon sequestration. The overall comparison of routes, based on simple figures-of-merit, shows a clear division between those using renewable energies and those associated with the traditional 'high energy density' primary sources. Emerging from the work is a clearer view of the implications of following a particular production path, the limitations of certain technologies and the research challenges which must be met in addressing future fuel options and global warming. © 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
