The conversion of biomass in supercritical water is a promising process for the generation of hydrogen - together with carbon dioxide and minor amounts of methane. Due to the special properties of supercritical water, biomass is fast degraded and the unwanted polymerisation to tar and coke is depressed. Both effects are reasons, why the gasification occurs even at 600-700 degrees C, a much lower temperature than necessary for the gasification of dry biomass.