Potential of Technosols Created with Urban By-Products for Rooftop Edible Production

Abstract

Urban agriculture is sprouting throughout the world nowadays. New forms of urban agriculture are observed such as rooftop farming. In the case of low-tech rooftop farming projects, based on recycled urban waste, one of the key issues is the type of substrate used, as it determines the functions and ecosystem services delivered by the green roof. Using a five year experimental trial, we quantified the food production potential of Technosols created only with urban wastes (green waste compost, crushed wood, spent mushroom), as well as the soil fertility and the potential contamination of food products. Regarding food production, our cropping system showed promising results across the five years, in relation with the high fertility of the Technosols. This fertility was maintained, as well as the nutrients stocks after five cropping years. Most of the edible crops had trace metals contents below existing norms for toxic trace metals with nevertheless a concern regarding certain some trace metals such as Zn and Cu. There was no trace metal accumulation in the Technosols over time except for Zn. This study confirmed that constructing Technosols only from urban wastes is a suitable and efficient solution to design rooftops for edible production.

Uptake of potentially toxic elements by edible plants in experimental mining Technosols: preliminary assessment

“…Technosols are a new Reference Soil Group, from the World Reference Base for Soil Resources (IUSS Work Group WRB, 2006), of artificial origin, formed by mixtures of different wastes and non-hazardous by-products (Camps et al, 2008;Sayadi-Gmada et al, 2019). The main applications of Technosols are in agriculture, the recovery of degraded and/or contaminated soils, landfill coverage, and in areas affected by urban construction or infrastructure projects (Echeverria and Morel, 2015;Grard et al, 2020).…”

Urban areas, human health and technosols for the green deal

“…The second most prolific group involves the use of anthropogenic soils/Technosols as a substrate for GI development, by using municipal waste mostly for land reclamation (Barredo et al, 2020 ) and rooftops (Grard et al, 2020 ). Technosols benefit for climate change in the field of greenhouse gases management (Rees et al, 2019 ) also arouses interest in the scientific community and in the infiltration capacity for mitigation flood risk (Díaz-Sanz et al, 2020 ).…”

Constructed Technosols: A Strategy toward a Circular Economy

“…Several materials can be used to construct a technosol (Table 1), but they must show an adequate capability to support plant growth, usually in addition to other components. In recent years, different materials have been investigated to identify their suitability in terms of cost and performance [43], from natural substrates such as coffee grounds [46] to man-made recycled materials like concrete [47]. Some of these materials have already been used as growing media to support containerized plant production and in the creation of green roofs, e.g., a mixture of coco peat and perlite [48], heat expanded shale, slate or clay [49], mineral wool, vermiculite and volcanic rocks.…”

“…The same holds for the plants expected to host: pioneer, low-demanding plants can be used if a low soil quality is obtained in relation to the availability of materials. [46] It is fundamental to choose components properly, paying particular attention to the destination of the constructed Technosol: a park in the inner city would require a high global quality whereas, in the restoration of an abandoned mining area, a lesser soil performance might be acceptable. The same holds for the plants expected to host: pioneer, low-demanding plants can be used if a low soil quality is obtained in relation to the availability of materials.…”