This work employed a mixture of low-grade Mg scraps (LGMS) and citric acid-added seawater to generate hydrogen gas. Metal catalyst was not required for accelerating the reaction of H(2) generation in the Mg scraps/citric acid solution. LGMS in 20 wt% citric acid-added seawater could produce substantially higher H(2) volume than the LGMS in 5 wt% citric acid-added seawater. Purity of the generated H(2) was about 99% (after dehumidification). By filling H(2)-production reactor every 30 min with fresh seawater to which citric acid has been added, similar to 701 of hydrogen could be produced in 100 min. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.