The best known process of this kind is the so-called "vapour explosion" („Steam Explosion“) triggered by a sudden reduction of the pressure with the result, that stored water evaporates and the structures of the biomass breakes up. The production of carbon-rich solids is successful in the range of 200°C. This procedure is called "Hydrothermal Carbonisation". At higher temperatures, there is known a method for the production of hydrogen by precious metal catalysts ("Aqueous Phase Reforming"). At approx. 300-350°C biomass can be converted into a high-viscosity tar which has a higher heating value and a higher viscosity as well as a lower water content than liquefaction products from "dry" processes. In a wide range of temperature single-substance syntheses are also known e.g. furfurale erythrose, glycol aldehyde and milk acid made of carbohydrates. From these substances other basis chemicals and finally e.g. plastics are produceable. Near the critical point (371°C, 221 bar) biomass can be converted into methane and carbon dioxide in the presence of precious metal catalysts ("Catalysed Close-critical Biomass Gasification"). At higher temperatures of more than 600°C hydrogen and carbon dioxide are the predominating products ("Overcritical Biomass Gasification"). Typically for hydrothermal processes are - in comparison to "dry ones" developed from the coal conversion - the following process parameters: