Rooftop farming on urban waste provides many ecosystem services

Abstract

Urban farming, especially on rooftops, is a popular and growing topic in both the media and the scientific literature, providing a genuine opportunity to meet some of the challenges linked to urban development worldwide. However, relatively little attention has been paid to date to the growing medium of green roofs, i.e., Technosols. A better understanding of the influence of Technosols and the link with ecosystem services is required in order to maximize the environmental benefits of urban rooftop farming. Between March 2013 and March 2015, a pilot project called T4P (Parisian Productive rooftoP, Pilot Experiment) was conducted on the rooftop of AgroParisTech University. Urban organic waste was used, and results were compared with those obtained using a commercial potting soil, based on yield and trace metal concentrations, substrate characterization, and the amount of leaching. An assessment of the ecosystem services expected from the Technosols was undertaken in terms of the output of food (food production and quality), regulation of water runoff (quantity and quality), and the recycling of organic waste. Indicators of these ecosystem services (e.g., yield, annual loss of mass of mineral nitrogen) were identified, measured, and compared with reference cases (asphalt roof, green roof, and cropland). Measured yields were almost equivalent to those obtained from horticultural sources in the same area, and the Technosols also retained 74-84% of the incoming rainfall water. This is the first quantitative analysis of ecosystem services delivered by urban garden rooftops developed on organic wastes, and demonstrates their multifunctional character, as well as allowing the identification of trade-offs. An ecosystem services approach is proposed for the design of soilbased green infrastructure of this kind and more generally for the design of sustainable urban agriculture.

How Can Innovation in Urban Agriculture Contribute to Sustainability? A Characterization and Evaluation Study from Five Western European Cities

“…In this sense, the community-supported peri-urban farm (S3) is also one of the examples of the implementation of organic and ecological practices that build on the reciprocal interactions in the soil-plant ecosystem. To satisfy the nutrient demand of the crops, other case studies reflected the use of organic fertilizers, such as the use of manure in the peri-urban social cooperative (S2) or the peri-urban farm (S4) or the use of urban compost in the open-air rooftop garden (T5) [16,17].…”

Revisiting the Sustainability Concept of Urban Food Production from a Stakeholders’ Perspective

“…Finally, Forchino et al [44] and Maucieri et al [22] investigated the environmental impacts of aquaponics, where the production of fish and vegetables are integrated, paying attention to different production techniques [44] as well as the potential use of aquaponics as an educational tool [22]. On the other hand, Grard et al [47] quantified the ecosystem services provided by rooftop gardens that use organic waste flow from the city as a substrate, thereby improving urban metabolism and enhancing the local circular economy. While food production showed similar values compared to other productive systems in the study area, the study highlighted the potential of rooftop gardens to improve runoff water management in cities due to their high rainfall retention capacity.…”

Using constructed soils for green infrastructure – challenges and limitations

“…-Moderate ratios of mineral and organic content, generally refraining from the addition of more than 30 % organic matter is desired (Deeb, 2016a;Grosbellet, 2008;Vijayaraghavan, 2016) to avoid excessive loss of organic matter by oxidation (CO 2 emissions) or leaching, which will change soil volume.…”