The reactions of different food classes during alkaline subcritical water gasification have been investigated with a view on hydrogen gas production. Experiments were conducted with sub-stoichiometric amounts of H2O2 for partial oxidation. NaOH was added to aid sample decomposition, reduce char/tar formation and to promote water-gas shift reaction. In general, hydrogen gas production depended on the class of food wastes including their chemical structure. Carbohydrate-rich food waste (glucose, molasses, tropical fruit mixture, whey powder) produced higher H-2 gas yields than others (proteins and lipids). Lipid-rich samples were the most difficult to decompose into gasifiable intermediates and therefore produced the lowest H-2 yield. Generally, the addition of NaOH led to higher H-2 generation from all sample types. However, two separate side reactions namely, neutralization and saponification involving NaOH with protein- and lipid-rich samples, respectively were significant. Hydrogen production from carbohydrate-rich samples was most suited for the reaction conditions applied. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.