NOVELTY - The biogas plant for the production of biogas by fermentation, comprises a fermenter (2) in which a nutrient medium is introduced by an inlet opening (3), a control unit by which the abundance quantity of the nutrient medium is adjusted, a mixing device (10) in which the nutrient medium and gaseous medium are mixed, and a heat exchanger by which the process warmth required to the fermentation is supplied to the nutrient medium. The fermenter is connected upstream of the mixing device having a first inlet by which the nutrient medium is supplied to the mixing device.    USE - For the production of biogas by fermentation.    ADVANTAGE - The biogas plant has less operating and maintenance costs and ensures simple and cost-effective production of the biogas.    DETAILED DESCRIPTION - The biogas plant for the production of biogas by fermentation, comprises a fermenter (2) in which a nutrient medium is introduced by an inlet opening (3), a control unit by which the abundance quantity of the nutrient medium is adjusted, a mixing device (10) in which the nutrient medium and gaseous medium are mixed, and a heat exchanger by which the process warmth required to the fermentation is supplied to the nutrient medium. The fermenter is connected upstream of the mixing device having a first inlet by which the nutrient medium is supplied to the mixing device, a second inlet by which the gaseous medium is supplied to the mixing device and a third inlet by which the nutrient medium taken from the fermenter is supplied to the mixing device. The regulation of the abundance quantity takes place via a regulation of the supply and/or removal of the nutrient medium in the function of the pressure of the fermentation gas produced in the fermenter. The second inlet of the mixing unit is connected to a gas compressor and/or a gas pump (13). The fermenter has sampling points for entirely or partially fermented nutrient medium. The plant has a gas pipeline (12) through which the biogas taken from the gas storage area of the fermenter is supplied to the second inlet of the mixing device.    DESCRIPTION OF DRAWING(S) - The figure shows a biogas plant.    Fermenter (2)    Inlet opening (3)    Mixing device (10)    Gas pipeline (12)    Gas pump. (13)