From triangles to cycles

A modern waste management strategy is considered to be based on a hierarchy of solutions, often graphically represented by a triangle. The integrated solid waste management established by the European Union, organized according to five distinct steps (waste prevention, reuse, recovery and recycling of materials, energy recovery and safe landfilling of residues). A different vision of a virtuous waste management strategy is afforded by natural material cycles. These are biogeochemical cycles, by means of which an element (carbon, nitrogen, phosphorus, sulphur, etc.) is exchanged among the numerous components of the Earth (biosphere, geosphere, hydrosphere, atmosphere, etc.). In this vision the role of the landfill is strategically fundamental not only in closing the cycle of materials and waste, but also in the global carbon balance, totalling sequestration rates comparable with the ones of marine sediments, which are the most important natural carbon sink.