The COVID-19 pandemic unveiled the fragility of food sovereignty in cities and confirmed the close connection urban dwellers have with food. Although the pandemic was not responsible for a systemic failure, it suggested how citizens would accept and indeed support a transition toward more localized food production systems. As this attitudinal shift is aligned with the sustainability literature, this work aims to explore the tools and actions needed for a policy framework transformation that recognizes the multiple benefits of food systems, while considering local needs and circumstances. This perspective paper reviews the trends in production and consumption, and systematizes several impacts emerged across European food systems in response to the first wave of pandemic emergency, with the final aim of identifying challenges and future strategies for research and innovation toward the creation of resilient and sustainable city/region food systems. The proposal does not support a return to traditional small-scale economies that might not cope with the growing global population. It instead stands to reconstruct and upscale such connections using a “think globally act locally” mind-set, engaging local communities, and making existing and future citizen-led food system initiatives more sustainable. The work outlines a set of recommended actions for policy-makers: support innovative and localized food production, training and use of information and communication technology for food production and distribution; promote cross-pollination among city/region food systems; empower schools as agents of change in food provision and education about food systems; and support the development of assessment methodologies and the application of policy tools to ensure that the different sustainability dimensions of the food chain are considered.
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.
Purpose New environmental strategies are emerging for cities to become more self-sufficient, such as hydroponic crop production. The implementation of such systems requires materials that usually originate in countries with low labour costs and other legal regulations. To what extent could these strategies be shifting problems across the globe? To answer this question, we performed a comprehensive environmental and social assessment of the various extended soilless systems used to grow vegetables on urban roofs. Methods Three different growing media constituents were chosen for this study: perlite, peat and coir; which are produced in three countries, Turkey, Germany and the Philippines, respectively, and are imported to Spain. By using a life cycle assessment, we evaluated the environmental performances of the production and transport of these growing media. Additionally, we performed a social life cycle assessment at different levels. First, we used the Social Hotspots Database to analyse the constituents in aggregated sectors. Second, we performed a social assessment at the country and sector levels, and finally, we evaluated primary company data for the social assessment of the constituents through questionnaires given to businesses. Results and discussion The coir-based growing medium exerted the lowest environmental burden in 5 out of 8 impact categories because it is a by-product from coconut trees. In contrast, perlite obtained the highest environmental impacts, with impacts 44 to 99.9% higher than those of peat and coir, except in the land use. Perlite is a material extracted from open-pit mines that requires high energy consumption and a long road trip. Regarding the social assessment, peat demonstrated the best performance on all the social assessment levels. In contrast, coir showed the worst scores in the Social Hotspots Database and for the impact categories of community infrastructure and human rights, whereas perlite displayed the lowest performance in health and safety. Nevertheless, coir and perlite evidenced much better scores than peat in the impact subcategory of the contribution to economic development. Conclusions This study contributes to a first comparison of three imported growing media constituents for urban rooftop farming from environmental and social perspectives to choose the most suitable option. Peat appears to be the best alternative from a social perspective. However, from an environmental standpoint, peat represents a growing medium whose availability is aiming to disappear in Germany to preserve peatlands. Therefore, we identify a new market niche for the development of local growing media for future rooftop farming in cities.
The main objective of this study is to analyse the barriers and opportunities with regard to the implementation of urban agri-green roofs (UAGR) in cities. The case study was conducted in Barcelona, a Mediterranean compact city. The World Café methodology and a semi-quantitative analysis were used in this work. Five categories of barriers and opportunities were discussed (social, environmental, legal/administrative, technological/architectural, and economic) by interdisciplinary stakeholders.In total, 103 barriers and opportunities were identified. The main barriers identified were as follows: the lack of information and social cohesion regarding UAGR projects; the Mediterranean climate; the lack of specific regulations and protocols; and the initial investment, the pre-condition of the roof and its load bearing capacity. The main opportunities identified were as follows: social cohesion, improved life quality, new specific regulations, the profits derived from UAGR projects and aesthetic improvement. The UAGR's scale of impact results showed a homogeneous distribution between "building" and "city", while the "global" scale remains residual. Regarding the stage of the UAGR life cycle at which barriers and opportunities emerge, the results highlight how most opportunities appear during the "use" stage of the roof, whereas barriers do so during the "project" stage.
With the overall aim to design successful implementation strategies of food-energy-water production systems on urban roofs, we propose an integrated process that includes participatory processes and a multi-dimensional sustainability assessment of environmental, social and economic indicators. The proposed framework was applied to a typical housing estate in the Metropolitan Area of Barcelona made up of 201 buildings and 13,466 inhabitants and characterized by a high share of low-income families. We assess several future scenarios of joint electricity production (photovoltaic panels), vegetable production (through open-air farming and greenhouses), green roof implementation and rainwater harvesting and rank them according to non-participatory and participatory approaches. In general, there was a tendency for residents to choose strategies providing energy and water rather than the food production potential of rooftops. However, the environmental assessment indicated that the least impacting alternatives from a life cycle approach were those promoting vegetable production, meeting 42 to 56% of the residents’ fresh produce demand and reducing environmental impacts by 24 to 37 kg CO2eq m−2 of rooftop/year. Hence, we found that residents were mainly concerned with energy expenses and not so much with food insecurity, social cohesion or the impacts of long-distance supply chains. Our assessment supports urban sustainability and helps identify and breach the gap between scientific and user preferences in urban environmental proposals by informing and educating residents through a participatory integrated assessment.
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