Towards Productive Cities: Environmental Assessment of the Food‐Energy‐Water Nexus of the Urban Roof Mosaic

• Published in: Journal of industrial ecology 2019-08, Vol.23 (4), p.767-780
• Main Authors: Toboso‐Chavero, Susana, Nadal, Ana, Petit‐Boix, Anna, Pons, Oriol, Villalba, Gara, Gabarrell, Xavier, Josa, Alejandro, Rieradevall, Joan
• Format: Article
• Language: English
• Subjects: Agricultura urbana; Carbon dioxide; Cities; Cobertes verdes; Construcció sostenible; Construction; Consumption; Edificació; Elements constructius d'edificis; Elements de tancament; Emissions; Energia solar; Energia solar fotovoltaica; Energies; Energy; Energy harvesting; Environmental assessment; Environmental impact; Exploitation; Feasibility; Feasibility studies; Food; Food production; Green roofs (Gardening); Industrial ecology; Life cycle analysis; Life cycle assessment; life cycle assessment (LCA); Life cycles; Methods, Tools, and Software; Neighborhoods; Optimization; Photovoltaics; Population density; Rain water; Rainwater harvesting; Rainwater recovery systems; Resource consumption; Resource self-sufficiency; Roofs; Solar energy; Solar heating; Urban agriculture; Water; Water harvesting; Àrees temàtiques de la UPC
• ISSN: 1088-1980; 1530-9290; 1530-9290
• DOI: 10.1111/jiec.12829

Summary Cities are rapidly growing and need to look for ways to optimize resource consumption. Metropolises are especially vulnerable in three main systems, often referred to as the FEW (i.e., food, energy, and water) nexus. In this context, urban rooftops are underutilized areas that might be used for the production of these resources. We developed the Roof Mosaic approach, which combines life cycle assessment with two rooftop guidelines, to analyze the technical feasibility and environmental implications of producing food and energy, and harvesting rainwater on rooftops through different combinations at different scales. To illustrate, we apply the Roof Mosaic approach to a densely populated neighborhood in a Mediterranean city. The building‐scale results show that integrating rainwater harvesting and food production would avoid relatively insignificant emissions (13.9–18.6 kg CO2 eq/inhabitant/year) in the use stage, but their construction would have low environmental impacts. In contrast, the application of energy systems (photovoltaic or solar thermal systems) combined with rainwater harvesting could potentially avoid higher CO2 eq emissions (177–196 kg CO2 eq/inhabitant/year) but generate higher environmental burdens in the construction phase. When applied at the neighborhood scale, the approach can be optimized to meet between 7% and 50% of FEW demands and avoid up to 157 tons CO2 eq/year. This approach is a useful guide to optimize the FEW nexus providing a range of options for the exploitation of rooftops at the local scale, which can aid cities in becoming self‐sufficient, optimizing resources, and reducing CO2 eq emissions.