Abstract: An apparatus for composting city sewage sludge and organic garbage to provide rich humus topsoil for city and private use. A continuous rotation of an aeration lift arm over the floor of a cylindrical tank, lifts the sludge to split it open to provide controlled dynamic aeration therewithin and to maintain bacteria action over periods of time and on demand in response to a temperature probe set at 150 degrees Fahrenheit. Cooperating equipment comprises an air blower, a motor driven arm operable upon a central drive sleeve device to rotate the aerator lift arm, and an exhaust pump for removing hot gases resulting from the bacteria action. The full compost mass is lifted over an inclined surface to a height and spilled over a raised trailing edge of the aerator arm closed with a back wall plate. The back wall plate has valved openings through which varying amounts of air are delivered from the hollow aerator arm to different radially volume-extended mass areas.