NOVELTY - Converting biomass of municipal, agricultural and/or industrial origin into carbon containing substances of different composition, comprises: adding water into the biomass; adding a catalyst into the water containing biomass; and subjecting the biomass enriched with water and catalyst to a thermal reaction in a pressure reactor under pressure, with the exclusion of air, and elimination of water, until a carbon containing end product is obtained. The reaction in the pressure reactor is initiated by the preheated, catalyst enriched biomass, which is preheated before and after thermal reaction.    USE - The method is useful for converting biomass of municipal, agricultural and/or industrial origin into carbon containing substances of different composition.    ADVANTAGE - The method: comprises the preheating of the biomass using the waste heat obtained from the pressure reactor and avoids the continuous reheating of the pressure reactor and thus the method is energy efficient; and can be carried in industrial scale.    DETAILED DESCRIPTION - Converting biomass of municipal, agricultural and/or industrial origin into carbon containing substances of different composition, comprises: adding water into the biomass; adding a catalyst into the water containing biomass; and subjecting the biomass enriched with water and catalyst to a thermal reaction in a pressure reactor under pressure, with the exclusion of air, and elimination of water, until a carbon containing end product is obtained. The reaction in the pressure reactor is initiated by the preheated and catalyst enriched biomass. The biomass is preheated before and after carrying out the thermal reaction outside the pressure reactor and is fed into the pressure reactor in the preheated condition. The biomass continuously passes through the pressure reactor, where the preheated portion of the biomass is surrounded by remaining portion of the biomass situated in the pressurized reactor. An INDEPENDENT CLAIM is also included for a device (100) for carrying out the above method, comprising at least one pressure reactor, which is composed of at least one inner reactor (2.1) and an outer reactor (2.2), where the outer reactor is provided with at least one discharge opening, and at least one heatable mixing container (1) present upstream to the inner reactor, which exhibits a gas-tight lockable lid and at least one filler neck arranged on the lid.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic front view of the pressure reactor.    Mixing container (1)    Inner reactor (2.1)    Outer reactor (2.2)    Domed lid (12)    Device for converting biomass of municipal, agricultural and/or industrial origin into carbon containing substances (100)