Manned activity within a closed environment will generate a variety of wastes, both stable and potentially biodegradable. The wastes can never be totally eliminated: waste management aims to make a change of form which is both advantageous in terms of volume and hazard reduction and which does not compromise crew health and safety. Micro-organisms will be carried on board by the crew and will be present in the wastes. The fundamental philosophy of our waste management concept is to specifically exclude or specifically include this inherent microbial activity. The complete safe stabilization of waste requires its exclusion while the ultimate need of element recycle will rely on microbial conversion processes.