Urban metabolism, sustainability and energy transition in cities: A comprehensive review

This research article conducts a comprehensive literature review on the concept of urban metabolism (UM), with a special focus on the transition from a linear to a circular model. In the context of climate change, increasing urbanisation, and resource depletion, cities are recognised as playing a crucial role in environmental sustainability. A bibliometric analysis of scientific literature shows an increasing interest in circular UM as a comprehensive approach to managing energy and material flows in urban settings. This article aims to further explore the transition from a linear to a circular model by reviewing the evolution of the urban metabolism concept, its key components, and relevant case studies from cities that have successfully implemented circular strategies. By identifying barriers and challenges cities face in adopting circular practices within their urban metabolism, the article proposes recommendations to overcome these obstacles. Furthermore, it examines the interrelationships between circular UM and the Sustainable Development Goals (SDGs), particularly in terms of sustainable urban planning and energy transition. However, important challenges remain, such as the lack of standardised and accessible data that hinder comparisons between cities and their evolution. Finally, future lines of research are proposed that focus on the integration of new technologies, such as artificial intelligence and neural networks, as well as the development of circular urban models that can tangibly measure their impact on climate change. This review provides a comprehensive overview of the current state of the art of UM while enriching the existing body of knowledge on emerging trends in this field.