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Urban Nexus

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

By Susana Toboso‐Chavero, Ana Nadal, Anna Petit‐Boix, Oriol Pons, Gara Villalba, Xavier Gabarrell, Alejandro Josa, Joan Rieradevall. 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.

The authors 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.

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Published

November 2018

In

Journal of Industrial Economy

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Modelling and Assessment

Publication // Dynamics of water–energy–food nexus methodology, methods, and tools

By Endo, A., Yamada, M., Miyashita, Y., Sugimoto, R., Ishii, A., Nishijima, J., . . . Qi, J. (2020). This review identifies the existing state-of-the-art methodology, methods, and tools that are developed and used within the WEF Nexus by reviewing articles published during the past three years.

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Events

Conference // Week on Water for Development in August 2020

Every drop counts – but what is happening in the water sector in times of COVID-19? The Week on Water for Development (WW4D) is a virtual five-day conference from 24 to 28 August 2020, organised by the German development cooperation (GIZ), that connects relevant stakeholders around key topics on water from COVID-19 to climate change. WW4D is also part of SIWI’s Stockholm World Water Week at home 2020.

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Governance

Nexus Principles // The Water, Energy and Food security Nexus Principles

The Water-Energy-Food security Nexus Principles guide towards the application, implementation and operationalisation of the Water-Energy-Food security Nexus (WEF Nexus) approach in different contexts. The Principles were developed by practitioners based on their experience and grounded in research.

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