Abstract: A compost bin module for aerobic decomposition of organic matter. The module is in the form of a container comprising a free-standing portable structural frame for placement on or above the ground. It further comprises removable sidewalls, and an open top and open bottom. Each of said removable side walls insertable into the structural frame and laterally restrained thereby. The structural frame comprises at least three spaced-apart posts, at least an equal number of structural members spanning between and interconnecting the posts, each of the structural members spanning between two adjacent posts at or near their base.