In our times, the notion of a cycling economy is the predominant paradigm. There is no doubt that reuse and recycling conserve energy and resources, and that they contribute significantly to reduce pollution. But it is also a fact that waste management is a key element for controlling linear flows, too. Like natural systems, man-made systems produce residues of no further immediate use that cannot be recycled. Examples comprise materials with constituents that have been banned because of the hazard they pose, such as asbestos in construction material, heavy metals and flame retardants in plastic and wood waste, chlorofluorocarbons (CFCs) in coolants, or polychlorinated biphenyls (PCBs) in capacitors. These waste materials need to be disposed of in a safe place, a so-called ‘sink’ (as an antonym to ‘source’).