The invention relates to a pulper and to its method for recycling wastes and/or product residuals. The pulper comprises a tank is which a rotor is provided for defibrating the stock mixture to be recycled, as well as a screen for drawing off the defibrated outfeed from the tank, the rotor being powered by an electric motor comprising a drive shaft in active transmission with the rotor. In accordance with the invention the electric motor is configured as a three-phase synchronous motor for operation in a speed range from 0 to 1000 rpm. It is connected to the output of a frequency inverter controlled by a controller, the output of the drive shaft being directly connected to the rotor.