The present invention provides a device for mixing material. The device comprises a mixing container having a bottom and a vertical wall, at least one mixing element provided in the mixing container and drive means for driving said at least one mixing element. The device comprises a buffer container having a movable buffer bottom and a vertical buffer wall, which is disposed above said at least one mixing element, as well as further drive means for moving the buffer bottom between a closed position and an open position. The invention further provides a method for using such a device.
