NOVELTY - A composting apparatus comprising a sealable container, an aerator for actively transporting gaseous material, conduits for conducting gaseous material into and out of container, damper(s) within the conduits for allowing or restricting gaseous material transport, an air sensor for sensing condition within the apparatus, and a controller for controlling the damper responsive to the sensed condition, is new.    USE - The apparatus is useful for composting source materials, e.g. organic materials including hazardous and toxic materials. It can be designed as an intermodal container which may be handled and transported using handling and tipping equipment commercially available.    ADVANTAGE - The inventive apparatus enables convenient, low-cost, efficient, odorless, sealable, and not labor intensive in-vessel composting process.    DETAILED DESCRIPTION - A composting apparatus comprises a movable, sealable container having a base and sidewalls defining a central cavity, a perforated floor within the cavity, and first and second gas-permeable ports; an aerator for actively transporting gaseous material through the gas-permeable ports; conduits (32) for conducting gaseous material into and out of the container; damper(s) (44) within the conduits for allowing or restricting gaseous material transport; an air sensor for sensing condition within the apparatus; and a controller for controlling the damper responsive to the sensed condition. The air sensor has inputs distributed at spaced points within the conduits to be unaffected by common turbulence. When the composting apparatus contains source material, the gaseous material is actively transported from one of the gas-permeable ports through the perforated floor evenly through the source material, and subsequently through the other gas-permeable port.    DESCRIPTION OF DRAWING(S) - The figure is a cut-away view of an air conduit.    Conduit (32)    Damper (44)    Shaft (45)    Differential air-pressure sensor (48)