A small portable housing forms a trash compacting chamber in the bottom. At one side of the housing interior, above the chamber, is a space through which trash can fall to the chamber from an upper trash compacting opening. At the other side of the interior of the housing and above the chamber is the compacting mechanism powered by a hydraulic ram. This mechanism includes a carriage supporting a two-part platen, one part of which is below the ram and fixed to the carriage and the other part of which is articulated for movement between a vertical position when raised, and a generally horizontal position across said space when being lowered. Several lost motion mechanisms are disclosed for initially so moving the articulated portion as the ram is extended and thereafter providing carriage movement. A gate is mounted to swing across the space when the platens are lowered so as to catch any trash introduced at that time. A counter is actuated by the opening of a door at the access opening and after a plurality of actuations initiates a compaction cycle. As an alternative to the counter, a timer is employed to cycle the compactor periodically.