What is the UCA?

The Urban Circularity Assessment (UCA) is an urban, economy-wide material flow and stock accounting method, which, paired with indicators, enables the assessment of material circularity of a municipality or city. Similarly to Economy-Wide Material Flow Analysis (EW-MFA), the method presented here is more than a compilation of data. When joined with indicators, it provides systemic and synthetic insights into cities' resource requirements and circularity. It aims to maximise circularity insights while reducing data needs and staying scientifically sound, easily transferable, and comparable to national and EU statistics.

In short

The UCA approach captures material movements and stocks aligning with circular economy efforts and providing insights to improve urban resource utilisation and reduce environmental impacts. It is based on existing literature and data sources, tailored for urban scales to simplify the assessment process for cities. It empowers public administrators, waste companies, and practitioners to understand and enhance resource utilisation while addressing environmental concerns within their administrative boundaries. It is time for cities to begin on their urban circularity.

Three main parts

The UCA consists of three main parts: (1) (a) material flow and (b) stock accounting (MFSA), (2) indicators and (3) CE assessment.

• Linking all of the entering and exiting flows to economic activities
• Determining material stocks and showing the complex nexus of metabolic flows
• Assessing circularity with circularity indicators

Material Flow Accounting

The evaluation of 29 urban material flow accounting methods and the Sector-wide Circularity Assessment (SCA), led to the decision to adopt and improve Eurostat's Economy-Wide Material Flow Analysis (EW-MFA) for urban contexts. This method is already used by European member states and the European Circular Economy monitoring framework. To contextualise this method and specifically the Mayer et al. (2019) framework at the urban level, some specific geographical and economic characteristics, i.e. accounting for imports and exports to a city were adjusted for the method that was designed for the national level. The proposed method aims to provide insight into traditional EW-MFA studies by including secondary material flows, enabling the monitoring of socio-economic loop closing.

The material flow accounting component of the Urban Circularity Assessment (UCA) utilises existing databases and Eurostat nomenclatures to ensure consistency with national and European initiatives. The system boundaries for the analysis include spatial boundaries corresponding to municipal/administrative limits, temporal boundaries covering two reference years for trend analysis, and material boundaries encompassing a range of materials and waste categories. The data collected is used to generate Sankey diagrams and calculate indicators.

Material Stock Accounting

To enhance and complement insights obtained from Material Flow Accounting, a bottom-up Material Stock Accounting (MSA) is carried out for the UCA. MSA enables to contextualise the accumulation of flows and the generation of Construction Demolition Waste (CDW) within cities (while exploring the potential of closing material loops through reusing, repurposing and recycling). The MSA focuses on the building stock within cities, as it represents a significant portion of the total material stock and is relatively easier to assess. The MSA method, based on the work of Stephan and Athanassiadis (2017), involves three main steps:

• gathering information on building location, land use, and floor area;
• determining building typologies;
• analysing the material composition of these typologies (t/m²).

The system boundaries for MSA include spatial boundaries aligned with administrative limits, a single reference year, and material boundaries based on available data. MSA enables the visualisation of material stocks through maps and explores potential building materials to be released and reused in the future.

Indicators

Data collected from material flow and stock accounting are analysed using an indicator framework to measure urban circularity. The framework includes direct and indirect indicators, assessing material flows, ratios, productivity, and loop closing efficiency. These indicators provide insights into resource utilisation, circularity levels, and the impact of materials on the economy.

21 indicators

Ten direct or scale indicators have been proposed that allow to dimension material flows, while another eight indirect circularity indicators exist to be able to analyse ratios, productivity and intensity and three are used for balancing. Scale indicators can reveal not just the types and amounts of natural resources entering the economy, but also what happens to materials as they transit inside and outside the economy, and how this affects resource productivity meanwhile the circularity indicators allow analysing the degree of loop closing and its efficiency.

Circular Economy Assessment

Assessing the data visualisations, Sankey diagram and indicators is crucial to determine the circularity of material flows and material categories within a city. These indicators allow for trend analysis and benchmarking against EU or national objectives. However, local information should complement the indicators to enrich the analysis and identify solutions specific to the city’s circumstances. (Therefore, Metabolism of Cities has included qualitative input in the Circular Hotspot Analysis (CHA), which is a potential next step of UCA).

Further information

Do you want to find out more (about the single parts)? Then we invite you to watch the video below and to go to the respective Handbook sections:

• (1a) Material flow accounting

• (1b) Material stock accounting

• (2) Measuring indicators

• (3) Assessing circularity

Outline of the video

• 0:23, What is the Urban Circularity Assessment? In a few words, Urban Circularity Assessment or UCA, is the addition of a number of parts. Material flow accounting, material stock accounting, indicators and then we actually assess.
• 0:43, Material flow accounting is to measure what enters and exits your economic or territorial system. So for instance, we will look at how much we extract locally, how much we import, how much we export, how much waste and emissions we emit by making this territory function. These are flows and as you see here, we have extraction, imports and exports, waste and everything that is actually consumed.
• 1:18, Stocks are what stay within our system. And this is crucially important because this is a buffer between resources intake and the emissions or waste outtake. That means that we need to measure what stays within a system for a longer period of time. That can tell us what are the potentials, the potentiality of reusing these materials in the future or if we don't do it, how much waste from construction and demolition waste will appear. So in that sense, we measured a bit like a scale, how much the city weighed.
  • 1:56, We did this essentially for residential buildings and non-residential buildings, mostly buildings, not roads, not cars, not the other things that we could have added because buildings are the heaviest within an economy.
• 2:13, Indicators, those indicators are a way to measure the pulse of the flows and the stocks.
  • Are they going in the right direction?
  • Are they going up?
  • Are they going down?
  • And is this good or bad for our economy?
• 2:42, Assessment: the other accounting parts measure, the indicators help us to give us a trend, a direction and then assessment is the interpretation.
  • What does it mean to have that many flows for a given territory?
  • What is the context like?
  • Can we reduce them?
  • Who will reduce them?
  • What type of economic models do we need to do all of these?
• 3:20, Why do we do it? Why is it so useful and how can we mobilise it?
  • It's very helpful to carry out that circularity assessment to develop, to launch your circularity journey.
  • It kind of tells you, ok, this is what matters, this is where you are today. This is where you should move tomorrow.
  • It also helps you to become a data expert, circularity assessment expert and make data speak for you.
  • develop evidence based or data driven policies
  • can also help you knock on some doors, you know, and your colleagues in the energy department, colleagues of the water department, co colleagues of the environmental or carbon department and try to get all together around the same table and collaborate based on a vision of a circular economy.
  • 4:22, Lastly, it enables you to find where you should put your efforts, where you should spend money, where you should put infrastructure, where you should make actions and action plans in order to become more circular, let us just give you some insights.
• 4:42, Output and results, you get these circularity diagrams or Sankey diagrams and these are for two different cities, Apeldoorn and Bodø. Once we have carried out these circularity assessments, what they told us is that these economies and many European cities are linear and open systems, meaning that there is a lot of throughput coming in and being consumed and going out as waste. Very little of these flows are re-entering the economy as secondary materials.
• 5:37, What can be done with the results: So once we know all of that, the idea is that we find these red dots that we can add, knowing where to add and how to add. For instance:
  • we could decrease the import dependency of some flows of fossil fuels
  • we could decrease the amount of emissions with renewables,
  • we could decrease the amount of landfill we have in order to make more recovery
• 6:15, material stock component, as a buffer. You can also spatialise this buffer to know where materials are going to appear and when this is highly valuable for spatial planning resource use and waste management
• 6:34, indicators we mentioned here is just a list of some of the indicators that we measured. These were inspired by colleagues in Austria. And we tried to re-calibrate them for a city level, all of them together, all of the results.
• 7:04, The dashboard: Everything comes together at the end in a dashboard, what we call the Urban Circularity assessment dashboard and over there for each of the cities that we have helped or that we have worked with, we create this dashboard when we have a brief idea of the circularity, the input circularity and the output circularity, the Sankey diagrams, we then know the context of the city, we then know how to act and what to do and we keep progress.