# Constructed Technosols: A Strategy toward a Circular Economy
## 2 Constructed Technosols  
According to the World Reference Base for Soil Resources (WRB) [35], Technosols include _ soils whose properties and pedagesis are dominated by their technical origin. They contain a significant amount of artefacts (something in the soil recognizably made or strongly altered by humans or extracted from greater depths) or are sealed by technic hard material (hard material created by humans, having properties unlike natural rock) or contain a geonembrane. They include soils from wastes (landfills, sludge, cinders, mine spells, and ashes), pavements with their underlying unconsolidated materials, soils with geonembranes and constructed soils._  
In recent years, some pedological engineering studies [36; 37] showed the ad hoc construction of Technosols (thus the punctual formulation of soils with the correct physical and chemical parameters for the studied or remediated site) as a potential solution for restoration of mined lands and urban greening.  
Usually, the demand for restoration of brownfields, dismissed sites, and polluted areas has been met with the development of remediation techniques designed to remove or immobilize the contaminants from the soil. These techniques, although often efficient, are usually very expensive, favoring the removal of the contaminated soil and its replacement with clean soil or soil material. To avoid the use of soil excavated from uncontaminated areas for this purpose, appropriate purpose-designed Technosols have been constructed to be placed on the affected site. These constructed soils are intended to be fertile substrates for plant growth even if their composition is sometimes far from the ideal.  
Figure 1: Layering of a sealed Technosol: artificial and natural materials are superposed to reach the prescribed level (photo F.A.M.).  
In the urban areas of the developed countries, the demand for green areas is increasing; this is due in part to a change in the way of living and expectations of urban dwellers and in part to the reduction of the industrial framework that left large, dismissed areas behind [38]. If, on the one hand, extensive areas with poor-quality soils are available, on the other hand city transformations produce large amounts of excavated materials--e.g., from the construction of underground lines--that must be disposed of. In addition, more and more frequently municipal organic waste is collected to be recycled as compost. The import of fertile agricultural soil from surrounding areas is becoming less and less feasible from many points of view: agronomic, environmental, and economic. In view of the necessary ecological transition [12], constructed soils appear to be an attractive and modern solution to respond to the urgent request of green areas within the urban fabric, with the aim to obtain a suitable substrate for plant growth [39]. Such solutions are currently studied worldwide; for example, in Roubaix (France) an experimental plot with constructed soils has been placed inside the \"Ecoquartier de I'Union\" [40], while in New York (USA) technosols made from waste have been tested to be used for urban gardening [41]. In the near future, the development of good quality soils for horticulture in urban spaces may lead to the realization of cultivated urban areas intended for providing food supplies for citizens [42].