Universiteit Leiden

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The city as an urban mine

Raw materials should no longer be excavated from mines, but reused from sources that are already present, such as unused underground electricity cables and discarded ships. At least, that is necessary for a circular economy. A new report explores where these resources are located and how we can use them.

Closed cycles

The Netherlands has set a goal to become a circular economy, in which cycles are closed as much as possible. The aim is to introduce as few primary raw materials as possible. This also means that a larger share of the demand for raw materials will have to come from secondary production. The main source of raw materials for the Dutch economy will, therefore, have to shift towards urban mining. Raw materials from geological reserves will no longer be mined from the soil but from stocks in society. However, insight into these stocks and their dynamics is largely lacking.


Voorraden in de maatschappij: de grondstoffenbasis voor een circulaire economie. By: Janneke van Oorschot, Jochem van der Zaag, Ester van der Voet (Leiden University, CML), Vincent van Straalen, Roel Delahaye (Statistics Netherlands)

The report was written as part of the 'Monitoring en Sturing Circulaire Economie Nederland' programme, led by the PBL 
Netherlands Environmental Assessment Agency. The programme aims to gather knowledge and to develop monitoring tools that are necessary for a circular economy in the Netherlands. More information can be found on the PBL website: Werkprogramma sturing en monitoring circulaire economie (in Dutch).

Click here to see the full report. 

Stored materials

Therefore, scientists from Leiden have written a report together with colleagues from Statistics Netherlands to gain more insight. In the report, they present an exploration of materials stored in stocks of goods in use: materials in the electricity system, in electronics, and in vehicles.

Steel from ships, aluminium from electricity cables

It appears that these stocks contain enormous quantities of raw materials: billions of tons of steel, aluminium, copper, and many critical metals. Potentially, the largest source of steel is ships. Discarded ships are now demolished elsewhere, but can also be seen as an opportunity for Dutch secondary production, the researchers say. Copper and aluminium can mainly be found in electricity cables, part of which is no longer in use but is still in the ground. Electronics can be a source for all kinds of critical materials that are needed to build an energy system based on renewable sources in the future.

More research

In the coming years, research into stocks in society will be continued. Attention will also be paid to the dynamics of stocks, the inflows and in particular the outflows, and the possibilities to re-use these outflows in our society.

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