Indicators for the Circular City: A Review and a Proposal

The theme of indicators for the circular city is currently much debated in the literature as a possible strategy for achieving sustainability in urban areas. However, it still has many features in the making, one of the most important being the issue concerning monitoring and the tool through which to achieve it.

In this paper, written by Federica Paoli, Francesca Pirlone and Ilenia Spadaro, the “indicator” tool is explored in depth. Currently, most existing indicators are associated with specific aspects of the circular economy. There have been few examples of indicators designed to assess the circularity of an entire city.

The paper aims to identify priority themes and describe a set of indicators to be used at the urban level. In the absence of an established reference frame, themes and indicators were identified through a methodology starting with an extensive literature search and careful analysis of the scientific literature. A particular result of this research is the definition of a minimum set of indicators common to all cities, which can be applied for comparative purposes.


Nowadays, the topic of the circular city is much debated in the literature and is seen as one of the possible solutions for achieving sustainability in urban areas. The transition to circular cities is at the center of this debate.

The basis of this vision is the employment of circular economy ideals. Those include the concepts of second use, remanufacturing, efficient use of resources, elimination of waste, avoidance of toxic materials, and improving and making sustainable waste management through the utilization of the 9Rs strategy (reduce, reuse, recycle, recover, reject, repair, refurbish, remanufacture, and reuse)

It has been reported that by applying the circular city model, Europe’s gross domestic product (GDP) can be increased by 7%. This would bring yearly savings of 600 billion euros, benefits of 1.8 trillion euros each year, and the creation of 170,000 jobs by 2035. Furthermore, carbon dioxide discharges could be diminished by 48% by 2030 and 83% by 2050. Over a similar period, raw material utilization can be decreased by 32% and 53%.

This study framework applies analysis at the city level, discretizing it into sectors which are key because they have the greatest potential for circular innovation, the greatest environmental impact, and the greatest demand on resources. For each of these sectors, there is a need to be able to close the loop. It is also essential to create circular activity in general that connects the different sectors. However, effective circular planning and decision-making requires an understanding of the flows of materials and energy that leave and enter cities, and are consumed, processed, or stored there.

The ability to collect and analyze this data helps to identify where and how to intervene and which circuits to close. It also provides cities with information about their economic activities, and allows them to link current initiatives and their potential to make the city more circular. In this context, identifying operational indicators is a priority for cities to plan their transition to circularity. This helps understand what parameters can be measured and where the population and other actors in the cities can have the greatest impact.

Today there are several tools that have been adapted for assessing circularity in urban settings, but few that have been designed specifically for the purpose. Above all, such a tool should include all the actors and the various sectors that are involved in the process.

Cities currently play a dominant role in the world economy. Therefore, this study paper approaches the topic of circular cities by identifying indicators common for all cities, so that they can be compared with each other.

Materials and Methods

How to measure circularity in the urban context is one of the questions frequently asked in the recent literature, and the answer is by no means obvious.

It’s important to define what we consider relevant, what can be measured and what is worth measuring. It is not always possible to apply every indicator, because of a lack of data or because similar analyses have been carried out using different indicators. There is a need to create a shared base of data and knowledge, that can measure the effectiveness of actions implemented in urban areas. Aiming to identify levels of depth, steps to evaluate the level of the circular economy in a city can be developed from various analyses:

  1. 1. Quantifying the circularity of the individual proposed project with respect to the issue in which it fits;

  2. 2. Assessing the impact of the project with respect to priority issues such as mobility, waste, energy, and reduction of inputs (land, water, and energy consumption) and outputs (waste and pollutant production);

  3. 3. Considering the urban neighborhood, it is essential to assess impacts on different related priority issues (waste, mobility, energy, etc.) to finally quantify the different projects implemented in the area.

Therefore, this study aims firstly to implement a reconnaissance of the existing indicators used in the literature. It secondly wants to propose a useful set of indicators to evaluate circularity at the urban level.

The approach began with investigation of the literature and the main documents and strategies, to identify the indicators currently used in relation to circularity. These indicators were separated within a framework according to the different priority areas at the urban level.


Based on the creation of existing indicator databases and their in-depth analysis, despite various difficulties, 33 indicators were selected that can be applied to urban realities with different conditions. Criteria for the selection of these indicators first included the number of sources found that propose the use of the specific indicator. Those that were already most widely used in the literature and official documents were adopted. Second, indicators were chosen whose unit of measurement was clear and easily measurable (and thus monitorable). Finally, it was essential to consider their applicability in the urban context by their breakdown into key areas (this necessity emerged because of specific analysis).

In terms of the presentation of the research results, the studies of existing indicators were divided into two different databases. The first created from scientific publications, and the second from official documents produced by various cities.

In addition to that, following the need for indicators quantifying the circularity of a city, it was decided to propose a selection of indicators. Aiming to enable in-depth analysis on a neighborhood/urban area scale, the database of indicators that was designed was divided into the key priority areas identified in the urban sphere (waste, mobility, energy, etc.), in order to assess their impacts on each priority issue, and to arrive in conclusion at a unified vision of the different issues in the urban sphere.

It was also decided to select some of the transversal indicators (environmental, economic and financial, and social and cultural dimensions) while maintaining their characteristics of transversality, with a view to being applied at lower thematic or project levels.

Above all, through the analysis of the indicators examined, it was possible to propose a selection of indicators useful for assessing the circularity of actions planned and subsequently implemented in a city. To find out more about the specific indicators, it is possible to read the complete report at the following link.


In conclusion, this study aims to bring to attention the highlighted problem. It also wants to suggest, if not a solution, at least a contribution to consider and a basis on which to build active and participatory discussion.

The creation of a minimum set of indicators representative of the main sectors within the urban sphere is, in the authors’ opinion, useful for comparing cities with each other, regardless of their particular characteristics. At the same time, it also helps avoiding the risk of circular cities becoming self-referential through the creation of their own indicators designed ad hoc for actions implemented by the administration.

In addition, another point to keep in mind when approaching these issues is that of participation. It is difficult to imagine how these strategies can be implemented, or even discussed, without placing the citizen at their center. However, too often we are confronted with a lack of data and difficulty in accessing relevant information. Development of user-friendly tools for all would greatly shorten the time needed to reach completion of the urban ecological transition, as it would enable direct interaction of the three pillars on which the circular city is based. Within this framework, monitoring tools should also necessarily be designed to be as inclusive as possible. Both with regard to the various issues under consideration and to the dissemination of information.

Due to its features of implementability and updatability, the tool proposed here could be a first step in the right direction. The discussion and exploration of circular city realization, and specifically means for its implementation and subsequent monitoring, is a fertile area of activity. This way, the growing number of circular cities and increased attention to the topic will fuel further research and enable implementation and improvement of the indicators presented in this study.


Do you want to find out more information on circular economy and its themes? Visit Tondo’s blog!

This text is an excerpt from an article published with the following reference: “Paoli, F.; Pirlone, F.; Spadaro, I. Indicators for the Circular City: A Review and a Proposal. Sustainability 2022, 14, 11848.”. It can be read in its entirety at this link.

Francesca Pirlone

Francesca Pirlone is Full Professor in Urban Technique and Planning at the Polytechnic School – Engineering of the University of Genoa. Professor in Urban Planning in several degree courses at the Polytechnic School of the University of Genoa.Her research interests includes: urban and territorial requalification; safety and security policies for urban and land planning territory; urban r... Read more

Francesca Pirlone is Full Professor in Urban Technique and Planning at the Polytechnic School – Engineering of the University of Genoa. Professor in Urban Planning in several degree courses at the Polytechnic School of the University of Genoa.

Her research interests includes: urban and territorial requalification; safety and security policies for urban and land planning territory; urban resilience; circular and sustainable city; sustainable waste management; sustainable and slow tourism; promotion of the local entrepreneurial spirit (start-ups creation and support); enhancement of rural areas and abandoned/unexploited villages. She has carried out an intense scientific activity in the university field also thanks to European research projects, as Scientific Manager (INTERREG II, III, IV, V, Leonardo Da Vinci, VI and VII Framework Development and Research Programs, Maritime Cross-border, MED, ENPI CBC MED) and national programs (PNRR, PRIN, PAR FAS) and thanks to several collaborations with local Administrations.

She is the contact person for the Circular City at the University of Genoa in Sustainable UniGe Group and the Contact person of the University of Genoa within the RUS- Network of Italian Universities for the working group on sustainable mobility.

She is Coordinator of the Master’s Degree Course in Building Engineering-Architecture at the Polytechnic School – Engineering of the University of Genoa. Lecturer in several Engineering Degree Courses at the University of Genoa.

She is a member of the teaching staff of the PhD in Sustainable Development and Climate change (PhD SDC).

She is on the Editorial board of the series “Città e territorio” by FrancoAngeli Edizioni (Milan) and she is a Reviewer for several scientific journals of Area 08.

She has authored more than 130 publications and participated as a speaker in several International and National Conferences.

She is a member of the Italian Society of Urban Planners (SIU), of the National Institute of Urban Planning (INU) and of the Association of Transportation Engineering (AIIT).