A device for the separation of biomass into a solid portion and a liquid phase to be fermented under the production of biogas comprises a mixing tank (2), which is provided with an inlet port (1) for the biomass to be separated, an influx port (3) for a process liquid to be supplied to the mixing tank and with a discharge for the biomass processed in the mixing tank, a pressing device (5) for the separation of the processed biomass discharged from the mixing tank, a sedimentation tank (6), a metering pump (4), and a heat exchanger to heat up the part of the liquid phase. The device for the separation of biomass into a solid portion and a liquid phase to be fermented under the production of biogas, comprises a mixing tank (2), which is provided with an inlet port (1) for the biomass to be separated, an influx port (3) for a process liquid to be supplied to the mixing tank and with a discharge for the biomass processed in the mixing tank, a pressing device (5) for the separation of the processed biomass discharged from the mixing tank into a solid portion that is led to a drying process (10) and into a liquid phase that is enriched in the mixing tank with the predominant portion of the well fermentable organic and inorganic plant components, a sedimentation tank (6), in which the portion of the liquid phase is enriched with suspended matters, and a metering pump (4), which feeds back the part of the liquid phase, which is removed from the suspended matters, after heating up into the mixing tank, during which the part of the liquid phase enriched with the solids is led to the fermentation process. A heat exchanger, which heats up the part of the liquid phase, which is fed back as process liquid into the mixing tank and which is removed from suspended matters in the sedimentation tank, effects by means of the heat dissipated from a motor fed with the biogas produced in the fermentation process.
