The transition towards a circular economy (CE) is increasingly recognized as a promising pathway to tackle pressing sustainability challenges at the city-level. Indicator-based frameworks, that is, integrated systems of indicators, are considered as useful tools for monitoring this transition. Yet, studies that map and assess such frameworks are scanty. This article addresses this gap by assessing 15 indicator-based frameworks applicable to measure circularity at the city-level. The identified frameworks were assessed using eight criteria (transparency, stakeholder engagement, effective communication, ability to track temporal changes, applicability, alignment with CE principles, validity and relevance to sustainable development). Additionally, 12 validity requirements were defined to assess to what extent the indicators in the frameworks reflect CE aspects. The assessment reveals a wide variation regarding the extent to which the frameworks match the criteria with none of them satisfying all. In addition, in terms of validity criterion, none includes indicators that fulfill all the validity requirements. Furthermore, most frameworks consist mainly of environmental indicators and only three include indicators reflecting aspects related to the four pillars of sustainable development (environmental, social, economic and governance). Further research could develop a standardized framework for measuring circularity at the city-level and improving existing frameworks.

As cities worldwide implement strategies to accelerate the transition toward a circular economy (CE), there is an increasing need for tools to monitor progress. However, a standardised metric for CE monitoring in urban areas is lacking. This study examines the potential of the EU Circular Economy Monitoring Framework (CEMF), an established indicator-based framework for measuring national- and EU-level circularity performance, as a monitoring tool for urban areas. For this purpose, available data sources that can support the framework's application at the urban level are mapped, and data quality is assessed following the pedigree matrix approach. Next, the CEMF indicators are computed for the urban area of Umeå, Sweden. The mapping showed limited availability of urban-level data, necessitating the downscaling of national-level data using proxy factors. Most available urban-level data are of high quality, while the quality of national-level data is reduced when used to compute indicators at the urban level. The application of the CEMF in Umeå indicates that there are areas where the municipality performs well, though further improvements are needed. We conclude that the CEMF has potential as a monitoring tool for urban areas. However, improvements in CEMF...s scope and data availability are recommended.

With the circular economy (CE) gaining more traction worldwide, local authorities are engaging in efforts to develop circular strategies at the urban level. Developing and monitoring such strategies require detailed quantitative information on material and energy flows, which can be obtained through an urban metabolism (UM) analysis. This study demonstrates a bottom-up approach to analyze UM at the sectoral level based on material and energy flow analysis (MEFA), aiming to examine its utility within the context of the CE. The analysis is performed for Umeå urban area (Sweden) with a 5-year timeframe (2017–2021). The application of MEFA provides a detailed quantitative description of material and energy flows per sector, indicating the critical sectors in terms of resource consumption and waste generation and the most significant flows. More specifically, it reveals that the construction sector and households are key sectors within Umeå’s UM and that construction materials, food products, fossil fuels, and drinking water are significant metabolic flows. Furthermore, the application of MEFA with a multi-year timeframe uncovers trends in consumption rates of materials and generation rates of waste and emissions, revealing, for example, the correlation of material consumption and waste generation with the level of construction activity. Overall, by illustrating the potential of MEFA to provide a detailed quantitative analysis of material and energy flows, this study emphasizes its utility in supporting the design and monitoring of circular strategies at the urban level. At the same time, it highlights limitations of the method and suggests areas for future research.

Purpose: This study aims to investigate how the coupling of Material and Energy Flow Analysis (MEFA) with Life Cycle Assessment (LCA) under an urban metabolism (UM) perspective (referred to as the UM-LCA approach) can support the design, evaluation, and monitoring of urban-level circular strategies. For this purpose, we apply the UM-LCA approach to the urban area of Umeå (Sweden) by expanding the goal and scope of a recent MEFA study conducted by the authors of the article.

Methods: The modeling combines MEFA with LCA and is performed both retrospectively and prospectively. The MEFA was performed in the prior study following a bottom-up approach to map and quantify material and energy flows in the urban system at the sectoral level. The quantified flows are used in the present study to construct the life cycle inventory (LCI) model of the urban system. The LCI model is first used as a basis of the retrospective LCA (rLCA), which is conducted to assess the environmental performance of the urban system with its sectors. The LCI model is then modified according to future scenarios and is used as a basis of the prospective LCA (pLCA), which is performed to assess the environmental implications of implementing circular strategies in the future.

Results and discussion: The rLCA shows that the construction and household sectors are major drivers of environmental impacts in the urban system, with households being the largest contributors to 11 out of 12 analyzed impact categories. It also reveals the most impacting flows within these sectors, including food in households and steel in the construction sector. These findings indicate that the construction and household sectors and their most impacting flows should be prioritized in a circular strategy. Furthermore, the pLCA highlights that a future circular strategy promoting reductions in the material used in these two sectors could lead to higher reductions in all impact categories, ranging from 4.3 to 8.6%, than a strategy focused only on recycling, which could lead to reductions ranging from 0.2 to 1.2%.

Conclusions: This study concludes that the UM-LCA approach has great potential to comprehensively analyze, both retrospectively and prospectively, the environmental performance of an urban system providing valuable insights that could support policy makers in designing, assessing, and monitoring urban-level circular strategies. However, further research should address identified limitations of the UM-LCA approach (e.g., limited available data, inability to consider social and economic aspects) to facilitate its applicability and enhance its comprehensiveness.

As local authorities worldwide increasingly embrace the circular economy (CE) concept, it is crucial to equip decision-makers with the necessary tools to design and monitor effective urban-level circular strategies. With this study, we introduce a novel framework for assessing the urban metabolism and circularity of urban areas to support decision-making within the CE context. The framework integrates a structured dashboard of 27 CE indicators with the urban metabolic life cycle assessment approach (UM-LCA), which couples Material and Energy Flow Analysis (MEFA) with Life Cycle Assessment. We developed this framework building on insights from two prior studies, where we explored the utility of MEFA and UM-LCA as decision-support tools within the CE context, and by identifying CE indicators in the literature based on the RACER (Relevant, Acceptable, Credible, Easy, Robust) criteria. To demonstrate the applicability and utility of the framework and examine its strengths and weaknesses, we applied the framework to the Umeå urban area in Sweden. The application of the framework provided a detailed quantitative analysis of material and energy flows and environmental impacts per sector within the urban area, indicating key sectors in terms of resource use, waste generation and environmental performance. It also provided a comprehensive evaluation of Umeå’s current level of CE development, highlighting areas of strength and improvement, and offered a prospective assessment of the environmental implications of potential future circular strategies. Overall, the framework proved to be a valuable tool for generating detailed insights into material and energy flows, environmental impacts and circularity, which can be particularly useful for the design, monitoring and evaluation of urban-level circular strategies. However, the application also revealed some weaknesses of the framework, including its significant data demands, complexity and limited capacity to capture social and economic aspects, suggesting areas for further research to fully unlock its potential as a decision-support tool.