More Circular City in the Energy and Ecological Transition: A Methodological Approach to Sustainable Urban Regeneration

Cities consume over 75% of natural resources, produce over 50% of global waste, and emit 60–80% of greenhouse gases. The scenario that by 2050 two thirds of the world population will live in cities, highlights how cities are still responsible for the growing consumption characterized by linear economic processes, with the production of various types of waste. In this unsustainable framework, the Circular Economy offers the opportunity to shape the urban system by means of rethinking the possibility to produce and use goods and services, exploring new ways to ensure long-term prosperity. The Circular City paradigm contains in fact all the principles of the Circular Economy: recovery, recycling, and sharing. In particular, Circular City also introduces actions related to the development of renewable energy communities, use of green materials, CO2 absorption approaches, and Proximity Cities. This work aims to develop a methodology to build a composite index (Circular City Index) capable of measuring the degree of implementation of urban policies that may enable an ecological transition of public assets. Circular City Index was applied to the military cluster of the city of Cagliari (Sardinia, Italy), a significant case study to guide circular policies in public properties for civil and military uses.