NOVELTY - The method for operating a fermentation plant with a fermenter (1), which is loaded with a substrate (1a), comprises percolating the substrate with percolates (2a) from a percolate container (2), withdrawing the biogas developed in the fermenter and/or in the percolate container over a percolation process, and processing the withdrawn biogas in a biogas processing device (3) and then introducing into the fermenter using a flushing line (4) for discharging the biogases developed in the fermenter during processing the resulting carbon dioxide-containing exhaust gas.    USE - Method for operating a fermentation plant with a fermenter.    ADVANTAGE - The method minimizes methane slip, and increases the efficiency of biogas production.    DETAILED DESCRIPTION - The method for operating a fermentation plant with a fermenter (1), which is loaded with a substrate (1a), comprises percolating the substrate with percolates (2a) from a percolate container (2), withdrawing the biogas developed in the fermenter and/or in the percolate container over a percolation process, and processing the withdrawn biogas in a biogas processing device (3) and then introducing into the fermenter using a flushing line (4) for discharging the biogases developed in the fermenter during processing the resulting carbon dioxide-containing exhaust gas and/or introducing the carbon dioxide-containing biogas into the fermenter from a further fermenter in a fermentation process using the flushing line for discharging the biogases developed in the fermenter, where the carbon dioxide-containing flushing gas is introduced into the fermenter, so that it is guided through the substrate such that the gas present in the substrate is replaced into the substrate-free volumes of the fermenter. The carbon dioxide-containing flushing gas is introduced into the base of the fermenter, and is distributed in the area of the base of the fermenter, so that the substrate is simultaneously flowed through from bottom to top with the carbon dioxide-containing flushing gas. After flushing with carbon dioxide-containing flushing gas, the fresh air is introduced into the fermenter over the flushing line. During the introduction of the carbon dioxide-containing flushing gas, the biogas discharge takes place over a discharge line. After finishing the flushing process with carbon dioxide-containing gas, the biogas discharge is blocked and an exhaust air line is opened. An INDEPENDENT CLAIM is included for a device for operating a fermentation plant with a fermenter.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of a device for operating a fermentation plant with a fermenter.    Fermenter (1)    Substrate (1a)    Percolate container (2)    Percolates (2a)    Biogas processing device (3)    Flushing line. (4)