Abstract: A composting bin is disclosed that is readily assembled from modular panels. The bin is made in superposed sections, each section being formed from ventilated sidewall modules assembled into a regular polygon, usually a square. A latching arrangement is provided at the ends of each sidewall module to unite it to adjoining modules. The sidewall modules have a double wall. An outer wall provides structural support and is preferably formed of spaced apart slats firmly mounted on a frame. The inner wall is formed from screening. Free air circulation is achieved through the spaces between the slats and screening into the interior of the bin. The sections are readily stripped from composting material held within the bin to allow ready access from the sides for removal or mixing.