What are the outputs?

The outputs of UCA provide cities with valuable data to support decision making, foster holistic thinking, and justify the transition to circularity. Outputs will help you highlight current consumption patterns, emphasise the importance of data quality, quantify building material stocks, and predict possible material availability.

Outputs are shown as visual charts to help you better understand the current condition and help you build your visual story. Circular Sankey diagrams visually illustrate the extent of material loss and can also show the breakdown of material categories, emphasising the need for strategies to enhance material loops. By leveraging UCA outputs, cities can make informed decisions, develop evidence-based policies, see clearly where to focus on and optimise resource utilisation.

There are three main outputs that the UCA can produce: (1) city understanding, (2) data visualisations and indicators, and (3) a report.

City understanding

Arguably the most important, albeit the least tangible outcome of the UCA is the understanding of the urban material system and its circularity. This really is the final product of the UCA that will especially be internalised by the person(s) carrying out the analysis, but that is ideally captured and consequently shared and made available to the public by various means.

This understanding of the urban system includes detailed knowledge around the size of the most important economic sectors in terms of economic output, employees, specific parts of the value chains that are covered in the city, location of infrastructure, and diversity of stakeholders. Moreover, the urban system can be apprehended in terms of the composition and magnitude of material flows that move through it. Even without indicators, a physical understanding of the system is generated. Yet, the indicators that are fed by the various data points eventually reveal and allow for an assessment of a city’s circularity (and the progress towards it). Overall, the UCA exposes what happens with the material flows of that city and uncovers a metabolic status quo.

Data visualisations, maps and indicators

To represent the metabolic functioning of the city, data visualisations and possibly a data dashboard will be created for each city. (The dashboard links to collected and processed data and brings them to life in the form of visualisations and indicators.) The visualisations illustrate the data of the city, depending on the type of data, either in traditional diagram styles such as bar or pie charts and/or as synthetic Sankey diagrams. The Sankey diagram depicts not only the proportions of the flows, since they are in relation to each other, but also contains the actual values for the general activities of the city.

Flow accounting outputs: Interactive datasets and Sankey diagrams

The output of the material flow accounting provides structured and documented data for a municipality/city, for two years. This data captures a wide range of input and output materials and processes, covering the entirety of the system, including domestic extraction, imports, domestic processing, waste generation, and exports.

Interactive datasets

The data can directly produce different visual outputs such as charts on single processes to represent the date in more detail or over several years. Through the optional use of the DataHub, interactive charts can be created, allowing for easy embedding and display. The interactive charts facilitate comparisons between reference years, enabling a better understanding of changes over time.

You can click around in the below chart to explore the functionalities.

Sankey diagrams

Through the use of a Sankey diagram displaying the various material flows and their pathways, it helps cities to get a quick overview of the significance of all materials in a city, of one year. Sankey diagrams can be colour-coded per material stream for an even better understanding of a material’s contribution to the system.

Stock accounting outputs: Material stock map and charts

The output from the material stock accounting is structured and documented data on building material stock for a municipality of one reference year, with the amount and kind of materials per building dependent on the local data. Based on this output, a number of visualisations can be generated to make the data better communicable and easier to understand.

The most comprehensive visualisations that are produced from the MSA data are choropleth maps. With the combination of spatial data, i.e. the location and outline of buildings, as well as building (material) data the information can be spatialised and therefore mapped, illustrating various details with the help of colour grading. Again, depending on the data, these maps are ideally produced on the building level, but the scales of postcodes or neighbourhoods are also possible when spatially accurate data are not available.

In addition to the choropleth maps, other charts can of course be produced with the building data as well. These include more common and easily generated visualisations in the form of bar or pie charts, for example. These can be employed in those cases where they can provide additional insights.

Building material stock map

The aim is to quantify the materials that every single building contains and represent them spatially on a map. Depending on the data availability around building typologies, age cohorts, building height and material intensities, different, specific quantifications and investigations can be made and also visualised. This helps cities to better explore the urban mine and manage secondary resources.

Check the map out for yourself

Building material charts

Determining and analysing the material stock of a city can, similarly to the material flow accounting, also be a data intensive endeavour. While the building material stock map contains a lot of data, it cannot easily reveal all the insights that can be gained. Therefore, additional building material and typology charts can be made to discover more about the residential and non-residential buildings in the municipality.


Indicators have their own illustrative function and monitor the progress of the local economy towards circularity. They are an essential part of the UCA, because through them it can be determined how the quantified flows and stocks are faring. The indicators give away the status quo and a first baseline from where cities can focus on improving their circularity in the future.

Altogether, these indicators depict several facets of circularity of the city. As such, they need to be considered in combination rather than in isolation when assessing circularity. In addition, these indicators can be compared to other cities or spatial scales (such as the country level). However, this has to be done with great care and use of the contextual elements from the UCA.

Finally, a total of 21 indicators can be made use of. The values measured from these indicators can be traced over two reference years to track the city’s progress towards circularity.

UCA Report

Upon conducting the UCA, it is recommended that you create a final report for the city to document your findings.

Find out more about the approach of writing a UCA report and content: UCA Report

Here are some example reports: Existing reports