Gerardo EzequielSpatial intelligence for cities, home
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CityLoops: Urban Circularity Assessment

A co-authored method for accounting for the materials flowing through and stored in a city, prepared for five CityLoops pilots, with my material-stock maps for Apeldoorn and Bodø.

Use
A published method with 18 indicators for accounting for the materials a city stores and moves, and building material-stock maps for Apeldoorn and Bodø. Estimates, not an audit of every tonne.
Where the work stands
The method and maps estimate urban flows and stocks from available evidence; they do not audit every tonne or survey the materials in each building. The Apeldoorn map credits 3DBAG building data and material intensities from Sprecher and colleagues. The two maps do not establish delivery of every proposed dashboard across all five pilots.

CityLoops, Closing the Loop for Urban Material Flows, was funded under Horizon 2020 grant 821033.

D4.4 method PDF (opens in a new tab)Open the Apeldoorn map (opens in a new tab)

Fig. 1 of 2

Gerardo’s Apeldoorn map, showing 3D buildings coloured by estimated total material stock, with the stock legend in tonnes.
Buildings coloured by estimated total material stock, in tonnes: pale yellow lowest, dark teal highest. Apeldoorn material-stock map, 2022. Map: Gerardo Ezequiel Martín Carreño. Buildings: 3DBAG; material intensities: Sprecher and colleagues. Basemap: CARTO and OpenStreetMap contributors. Screenshot: 11 October 2026.View full image (PNG, 1.2 MB) (opens in a new tab)

Fig. 2 of 2

Bodø building material-stock map: buildings coloured by estimated stock, with the Layers panel open on the left, showing the legend in tonnes and layers for typology, subtypology, age cohort, concrete and wood.
Bodø building material-stock map: buildings coloured by estimated stock, with layers for typology, subtypology, age cohort, concrete and wood. Legend as printed on the map: Material Stock quantified [tonnes], 0.58 to 8.30. Apeldoorn’s legend runs 2.4 to 151,132.9 tonnes; the two maps are not drawn on a common scale. Map: Gerardo Ezequiel Martín Carreño. Basemap: CARTO and OpenStreetMap contributors. Screenshot: 16 October 2026.View full image (WebP, 231 KB) (opens in a new tab)
My role
Co-author and map developer
Period
2022–2023
Status
Completed research
Focus
Method for five CityLoops pilot cities; maps for Apeldoorn and Bodø

The question

Cities need a practical way to understand how materials enter, accumulate within and leave their boundaries. Local data are often incomplete, so the method had to balance scientific comparability with what municipal teams could actually collect and use.

My contribution

At Metabolism of Cities, I co-developed and co-authored D4.4, the Urban Circularity Assessment Method, as one of four named authors. We combined material-flow accounts for two reference years with bottom-up building-stock accounting and 18 indicators. The method specified Sankey and dashboard outputs for facilitated application in Apeldoorn, Bodø, Mikkeli, Porto and Seville. I also developed CARTO maps of building material-stock estimates for Apeldoorn and Bodø, making the stock analysis explorable at building scale. I supported application across the five pilots, built Sankey and CARTO outputs and managed two analysts.

How I approached it

  1. Build on prior methods

    We built on D4.1’s review of 29 urban material-flow methods and adapted Eurostat’s economy-wide accounting approach to city scale.

  2. Connect flows, stocks and indicators

    We paired two-year material-flow accounts with building-stock estimates, documented mass balancing and downscaling, and defined indicators, Sankey diagrams and dashboard outputs for facilitated use in five pilot cities.

  3. Map the stock

    I developed CARTO maps of building material-stock estimates for Apeldoorn and Bodø, with typology and age-cohort views.

What exists

A published assessment method with 18 indicators, prepared for five European pilots, and public building material-stock maps for Apeldoorn and Bodø.

  • Named as one of four authors of CityLoops deliverable D4.4, Urban Circularity Assessment Method.
  • Ten scale indicators and eight circularity indicators, paired with material-flow and bottom-up building-stock accounts.
  • Public CARTO maps of building material-stock estimates in Apeldoorn and Bodø, with building typology and age-cohort views.
  • A documented path from data collection and mass balancing to Sankey diagrams, indicators and a city dashboard, prepared for five pilot cities.
Design choices and constraints
  • Adapt Eurostat accounting so city results remain comparable with wider statistics.
  • Pair material flows with building stocks to account for accumulated resources.
  • Document mass balancing and downscaling when local data are incomplete.

Data availability and quality differ between cities. The method needs to remain comparable while being usable by municipal teams.

Explore the work

Next step

For clients and teams

Material-stock estimates needed for a city or a set of buildings?

Discuss a project

For research collaborators

Building stock or circularity indicators you want to test?

Discuss a research collaboration

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