NOVELTY - The fermenter for continuous production of biogas from biomass (24) according to the principle of solid methanation, comprises a gas-tight sludge digester (2) in which a transport channel is formed for biomass with a loading area (14) at the beginning of the transport channel and an unloading area (18) at the end of the transport channel, a loading device that juts from outside into the loading area for supplying fresh biomass (28) into the sludge digester, and an unloading device that juts from the unloading area towards outside for discharging fermented biomass from the sludge digester.    USE - Fermenter useful for continuous production of biogas from biomass according to the principle of solid methanation.    ADVANTAGE - The fermenter ensures simple and efficient production of biogas from biomass with high-throughput.    DETAILED DESCRIPTION - The fermenter for continuous production of biogas from biomass (24) according to the principle of solid methanation, comprises a gas-tight sludge digester (2) in which a transport channel is formed for biomass with a loading area (14) at the beginning of the transport channel and an unloading area (18) at the end of the transport channel, a loading device that juts from outside into the loading area for supplying fresh biomass (28) into the sludge digester, an unloading device that juts from the unloading area towards outside for discharging fermented biomass from the sludge digester, a percolate distribution device for spraying the fermented biomass in the sludge digester with percolate, a biogas extraction device, a percolate storage device for intermediate storage of percolate from the separator, and a percolate control device for controlling the percolate filling level in the sludge digester, connected with the percolate distribution device. The transport channel for conveying the fermented biomass from the loading area to the unloading area comprises installations for active conveying of fermented biomass. The loading device comprises a mixing device for mixing the fresh biomass and fermented biomass. The second sludge digester comprises a second transport channel for biomass with loading area at the beginning of the second transport channel, and unloading area at the end of the second transport channel. Between the first and second sludge digesters, a reloading device is arranged in order to convey the partially fermented biomass from the unloading area of the first sludge digester in the loading area of the second solid digester. The unloading device conveys fermented biomass from the unloading area of the second sludge digester. The loading device, the reloading device and the unloading device comprise pumps for conveying the mixture of fresh biomass and fermented or partially fermented biomass. The pumps are spiral pumps. The unloading device comprises a separator for the separation of percolate from the fermented biomass conveying from the unloading area of the first or second transport channel. The mixing device is connected with the percolate storage. The percolate control device is connected with the percolate storage, the mixing device and the separator. The first and/or the second transport channel comprise a slope between the loading area and the unloading area. The slope in the transport channel is 1-2%. A stirrer is arranged in the unloading area of the first and/or second transport channels. The first and/or second solid digester comprises a gas-tight base plate, a gas-tight circular cylindrical external wall extending itself from the base plate in the height, a gas-tight circular cylindrical internal wall extending itself from the base plate in the height, a gas-tight cover that is connected with the external wall and internal wall, and a separation wall extending itself from the base plate between the external wall and internal wall. Between the base plate, the external wall, the internal wall and the cover, the transport channel is fixed with a ring-cylindrical form for the reception of the biomass. The loading device interfuses the external wall at a side of the separation wall and the unloading device interfuses the external wall at another side of the separation wall. An INDEPENDENT CLAIM is included for a method for operating a fermenter.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of a fermenter.    Gas-tight sludge digester (2)    Loading area (14)    Unloading area (18)    Biomass (24)    Fresh biomass. (28)