TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: A part of the second reaction space between reactor cover and overflow is a gas collecting chamber. A gas extracting device is arranged in the area of the gas collection space. The recirculation medium exhibits a medium for the absorption of the recirculate and a medium for delivering the recirculate, where the medium for absorption is arranged in the area of 0-20% of the height of the reactor vessel and the medium for delivering is arranged in the area of 60-80%, preferably in the area of 70-80% of the height of the reactor vessel, respectively based on the reactor cover. The substrate input and the medium have a common supply in the reactor vessel for delivering the recirculate. The substrate input is arranged in the area of 15-40%, preferably in the area of 15-30% of the height of the reactor vessel based on the reactor base. The reactor base at the tip of the cone has a solid removal agent to remove the fermentation residue. Preferred Method: A temperature (T1) in the range in the first reaction chamber is adjusted to 30-33 degrees C and/or a temperature (T2) in the second reaction chamber is adjusted to 35-38 degrees C. The substrate is preheated to a temperature in the range of 0.1-5 degrees C, preferably to a temperature in the range of 1-3 degrees C below the first temperature. The heat dissipated in the overflow of the digestate is used for preheating the substrate. The substrate is mixed with the recirculate in a ratio of 1:1 to 1:10, preferably 1:5 to 1:10. The substrate has a dry mass content of 1-20%, preferably 2-6%.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The growth carrier consists of plastic films, preferably polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyamide and/or polyimide, preferably consist of polyethylene or polypropylene. The growth carrier is micro-structured and/or coated with organic substrates, preferably with starch and/or its derivatives.