NOVELTY - Device for the digestion of low organic materials, comprises a bioreactor and solid separators over the bioreactor. The bioreactor (11) has a reactor vessel (10) with a cone-shaped reactor base (12), side walls and a reactor cover (14) and the number of growth carrier, at least one recirculating medium and at least one overflow. The solid separators have a cone-shaped bottom, and at least one inlet, which is connected with the overflow of the bioreactor. The solid separators accumulated on or below the level of the reactor base are arranged next to the bioreactor.    USE - The device is useful for the digestion of low organic materials e.g. manure, molasses, vinasse or similar low-viscosity medium.    ADVANTAGE - The bioreactor is suitable for substrates with low dry matter content; has a simple design, which can be operated with a minimum externally supplied energy; has high efficiency, so that the residence time can be minimized to few days and the care required during the service life is minimal.    DETAILED DESCRIPTION - Device for the digestion of low organic materials, comprises a bioreactor and solid separators over the bioreactor. The bioreactor (11) has: a reactor vessel (10) with a cone-shaped reactor base (12), side walls and a reactor cover (14), where at least one absorption device for attaching a number of growth carriers substantially parallel to the reactor cover and in the middle third of the reactor vessel is arranged in the inner side of the reactor vessel, where the area of the cone-shaped bottom up to at least one absorption device forms a first reaction chamber (13) and the area of the at least one absorption device up to the reactor cover forms a second reaction chamber; the number of growth carrier, which stretches from the reactor cover to the absorption device, at least one substrate input in the area of the first reaction space, where the substrate input has a first heat exchanger for controlling the temperature of the substrate in the substrate input; at least one recirculating medium, which is recirculated from the second reaction chamber into the first reaction chamber, where the recirculation medium has a second heat exchanger to control the recirculate in the recirculation medium; at least one overflow, which is arranged in the area of the second reaction chamber between the reactor cover and the recirculation medium. The solid separators have a cone-shaped bottom, where a solid removing device is arranged at the tip of the cone, which is connected with the substrate input of the bioreactor and at least one inlet, which is connected with the overflow of the bioreactor. The solid separators present on or below the level of the reactor base are arranged next to the bioreactor. An INDEPENDENT CLAIM is also included for the fermentation of organic low-viscous materials, comprising preheating the low-viscous organic materials to a temperature below a temperature (T1) in the range of 28-33 degrees C, where the temperature is increased itself to the temperature (T1) by the fermentation heat produced from the acetogenic bacteria contained in the substrate, which is present in the first reaction chamber; producing the temperature (T1) in the first reaction chamber by the further addition of colder Substrate, where a second temperature in the range of 35-40 degrees C is adjusted itself in a second reaction chamber, which is located above the first reaction chamber, by the fermentation heat produced from the methanogenic bacteria contained in the substrate; and recirculating the substrate from the second reaction chamber into the first reaction chamber, where the amount of added substrate and recirculate is calculated such that the temperature (T1) and (T2) in the first and second reaction chamber (13, 15) are constant.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of the device with a bioreactor and a solid separator.    Reaction container (10)    Bioreactor (11)    Reactor base (12)    First reaction chamber (13)    Reactor cover (14)