Abstract: Effective systems for separating, collecting and transferring organic waste from multi-unit residential buildings to deliver to composting centres are described which facilitate the reduction of contamination of the organic waste with non-compostable plastic bags. This is accomplished both by ensuring that the residents are constantly provided with compostable replacement bags for their kitchen caddies after each delivery of a bag by the resident to the recycling room, and through consistent marking that reminds residents of the system's requirements.