TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: A defined amount of heat energy produced during the combustion of synthesis gases in the synthesis gas engine is supplied to the drying device as drying energy. The electrical energy produced during the combustion in the synthesis gas engine is fed into a power supply system. The synthesis gas engine is coupled with the drying device using a heat pipeline, such that the engine waste heat is supplied to the drying device as heat energy. The synthesis gas engine is coupled with a power grid using at least one power line such that the electrical energy produced during the combustion of synthesis gas in the synthesis gas engine is fed into the power grid. The synthesis gas engine is upstream to at least a cooling device, in which the hot combustion gases from the synthesis gas device is cooled down to a defined combustion temperature. The cooling device fed at least with a liquid, bacteria, preferably methane bacteria, fermentation substrate from at least one of the fermenter of the biogas plant, preferably with manure exhibits a cooling container or cooling tower, through which the hot combustion hot gas before it is fed to the synthesis gas engine is passed through direct contact with the fermentation substrate. At least one of the fermenter of the biogas plant is led with at least a supply pipe to the cooling container or cooling tower and at least a return pipe is returned to at least one of the fermenter of the biogas plant from the cooling container or cooling tower such that the liquid fermentation substrate in the circulation of the biogas plant to the cooling container or cooling tower and back to the biogas plant, is preferably recoverable by using at least one recoverable device. The cooling container or the cooling tower exhibits an additional cooling device, preferably in the form of outer windwardly surrounding cooling coils and/or in the form of internal led to the liquid fermentation substrate and/or in the form of a cooling jacket by means of the heat absorbed from the liquid fermentation substrate, which is given or discharged into the cooling agent led in the cooling coil or in the cooling jacket. At least a cooling device, preferably at least one of the heat exchanger is arranged in the supply pipe, preferably in an area of a cooling container- or cooling tower inlet and/or in a return pipe, preferably in an area of a cooling container- or cooling tower outlet. The hot synthesis gas is supplied to the head side of the cooling container or the cooling tower, preferably such that hot synthesis gas is injected in the fermentation substrate by using at least a gas lance traveled from the head region to the bottom region. The biogas plant are provided with several gas lances. The gas lances are arranged apart from each other and are led over a manifold. Preferred Method: The combustion gases supplied to the synthesis gas engine is cooled using a cooling device to a predetermined combustion temperature below 70 degrees C, preferably below 35 degrees C prior to its entry into the synthesis gas engine. The cooling device fed at least with a liquid, bacteria, preferably methane bacteria, fermentation substrate from at least one fermenter of biogas plant, preferably with manure exhibits a cooling container or cooling tower, in which the hot combustion gas is cooled and cleaned, such that the hot synthesis gas from the synthesis gas device is passed directly through the liquid fermentation substrate, so that the defined residues, preferably tar is washed out from the synthesis gas and/or decomposed by bacteria. The liquid fermentation substrate absorbed in the cooling container or cooling tower at defined time and in a predetermined amount is recirculated back to the biogas plant, thus is supplied to at least a fermenter of the biogas plant. The fermentation substrate prior to the entry and/or after the discharge from the cooling container or cooling tower is cooled using at least one additional cooling device to a defined temperature. At least an additional cooling agent is provided, by means of which a defined amount of heat removed from the liquid fermentation substrate is absorbed in the cooling container and cooling tower and heated by the hot synthesis gas. A thermolysis is carried out in the synthesis gas device, in which the dried fermentation substrate is gasified at a temperature greater than 500 degrees C, preferably at 500-650 degrees C. The dried fermentation substrate in the drying device or one of the drying device downstream to the synthesis gas device and upstream to the pelletizing device is processed to pellets such that the dried substrate of the drying device is fed in the form of pellets. EXAMPLE - No suitable example given.