As the resource recovery from mixed waste streams are performed, new mixed waste streams are generated. Some of these waste streams does not fit well to existing waste management options, for example, they may hold a to low heating value to sustain combustion and they may have a too high carbon content to be accepted at non-hazardous landfills. Also various health and pollution risks may arise as well as practical handling issues due to the physical properties of such wastes. One such waste is the under sieve fraction generated when recovering metals and fuel from mixed waste streams using mechanical and magnetic separation tools. Such mechanical sorting is typically used for mixed wastes of different properties and particle sizes, such as houshold bulky wastes, construction and demolition waste, and at landfill mining materials. In this work, we examine the properties of one case of mechanical sorting of bulky wastes, including construction and demolition wastes. We analyse a broad spectrum of chemical, physical, and mechanical properties as well as some biological. Based on the data we develop recommendations for landfilling, what potential problems might arise and how to counteract them.