The increasing CO2 content in the atmosphere and the increasing demand for raw materials due to population growth makes the organisation of a post-fossil and sustainable era of energy and material Supply, and the development of new chemical processes for intermediates essential. One possibility is to use biomass as a renewable material source. This is the reason why several polyols (-> 1,2- and 1,3-propanediol; 1,2-butanediol; glycerol and in-erythritol), which are easily available from sugars via biochemical conversion or hydrogenolytic cleavage, were dehydrated in sub-and supercritical water (SCW). During the dehydration of polyols in SCW mainly aldehydes or furan derivatives are formed, which are important industrial intermediates. The focus was on the influence of electrolytes versus acids on the reactions. It could be concluded that converting polyols in sub- and supercritical water with the addition of bivalent transition metal sulphates is a well-promising approach to substitute crude oil based processes for the CO2-neutral production of intermediates from renewable resources. (c) 2006 Elsevier B.V. All rights reserved.