The present systems and infrastructures for the provision and management of food, energy, water and materials (FEWM) in cities are the result of several decades of evolution. Meanwhile, urban centres continue to change both in size and density, while technology has advanced and new threats of discontinuity have emerged (climate change, resource scarcity). New opportunities for more sustainable solutions are inspired by the concept of localisation, climate neutral development and a circular economy, where waste and threatening emissions no longer exist. It is crucial to explore and test such new technologies and integrated systems, including their use and feedback loops, to achieve increased effectiveness, sustainability and robustness to large-scale disruptions.
The concepts ‘urban metabolism’ and the ‘circular economy’ refer to urban areas as complex ecosystems. This approach deals with the dynamics of cities in relation to the scarcity, carrying capacity and conservation of mass and energy in urban networks and processes. The theme focuses on the exploitation of possible synergies at the metropolitan-scale level towards a more resilient and integrated sustainable food, energy, water and material nexus. It focuses on ‘design for circular reuse’ and integrated generation based on renewable sources, new carriers and services, storage and demand–supply matching through smart infrastructures, and, combined with green– blue urban environments based on integrated water, nutrient and material recovery, sharing services and demand–supply chain optimalisation. In this circular economy at the metropolitan level, loops are closed and waste no longer exists.