Abstract: A waste digestion unit which comprises a container, a waste inlet into the container, an outlet from the container for digested waste, a gas bleed outlet from the container and a stirrer for stirring the contents of the container. The inlet, waste outlet, bleed outlet and stirrer are arranged so that the container can be mounted in position and partially filled with waste to a level defined by the waste outlet to provide a gas space above the waste. In this position of the container the bleed outlet is above the waste level and, the inlet discharges into the container below the waste level. The stirrer is capable of stirring the waste at said waste level and below said waste level.