A unit for compacting waste prior to disposal provides a waste compaction unit for fitting into a housing comprising a lid and an interior for collecting waste. The compaction unit comprises a plunger comprising bellows housed in the lid; a pneumatic locking mechanism housed in the lid; and a pump connected to the plunger via the locking mechanism wherein the pump is arranged in operation to activate the locking mechanism prior to inflating the bellows to extend the plunger axially towards the interior of the housing such that any waste collected therein is compacted.