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Abstract Urban agriculture has emerged as an alternative to conventional rural agriculture seeking to foster a sustainable circular economy in cities. When considering the feasibility of urban agriculture and planning for the future of food production and energy, it is important to understand the relationships between energy flows throughout the system, identify their strengths and weaknesses, and make suggestions to optimize the system. To address this need, we analyzed the energy flows for growing tomatoes at a rooftop greenhouse (RTG). We used life cycle assessment (LCA) to identify the flows within the supply chain. We further analyzed these flows using ecological network analysis (ENA), which allowed a comparison of the industrial system to natural systems. Going beyond LCA, ENA also allowed us to focus more on the relationships between components. Similar to existing ENA studies on urban metabolism, our results showed that the RTG does not mimic the perfect pyramidal structure found in natural ecosystems due to the system's dependency on fossil fuels throughout the supply chain and each industry's significant impact on wasted energy. However, it was discovered that the RTG has strong foundational relationships in its industries, demonstrating overall positive utility; this foundation can be improved by using more renewable energy and increasing the recycling rates throughout the supply chain, which will in turn improve the hierarchy of energy flows and overall energy consumption performance of the system. Graphical abstract Unlabelled Image Highlights • The energy-food nexus in urban agriculture was studied through interindustry flows. • We conducted an ecological network analysis using life cycle data. • An integrated rooftop greenhouse was assessed as an innovative case study. • The energy trophic structure does not mimic efficient natural metabolic systems. • Energy dissipation could be improved through renewable energy. [ABSTRACT FROM AUTHOR]

Today, urban agriculture is one of the most widely used sustainability strategies to improve the metabolism of a city. Schools can play an important role in the implementation of sustainability master plans, due their socio-educational activities and their cohesive links with families; all key elements in the development of urban agriculture. Thus, the main objective of this research is to develop a procedure, in compact cities, to assess the potential installation of rooftop greenhouses (RTGs) in schools. The generation of a dynamic assessment tool capable of identifying and prioritizing schools with a high potential for RTGs and their eventual implementation would also represent a significant factor in the environmental, social, and nutritional education of younger generations. The methodology has four-stages (Pre-selection criteria; Selection of necessities; Sustainability analysis; and Sensitivity analysis and selection of the best alternative) in which economic, environmental, social and governance aspects all are considered. It makes use of Multi-Attribute Utility Theory and Multi-Criteria Decision Making, through the Integrated Value Model for Sustainability Assessments and the participation of two panels of multidisciplinary specialists, for the preparation of a unified sustainability index that guarantees the objectivity of the selection process. This methodology has been applied and validated in a case study of 11 schools in Barcelona (Spain). The social perspective of the proposed methodology favored the school in the case-study with the most staff and the largest parent-teacher association (social and governance indicators) that obtained the highest sustainability index (S11); at a considerable distance (45%) from the worst case (S3) with fewer school staff and parental support. Finally, objective decisions may be taken with the assistance of this appropriate, adaptable, and reliable Multi-Criteria Decision-Making tool on the vertical integration and implementation of urban agriculture in schools, in support of the goals of sustainable development and the circular economy. [ABSTRACT FROM AUTHOR]