Wheels of Metals: Urban Mining for a Circular Economy

Population and welfare are growing. Providing the world with metals is becoming a major challenge. Only by closing the loop will metals be available in sufficient quantities, not just now but also in the future: urban mining, the substantial re-use and recycling of metals. In this MOOC we will explore the challenges related to metals supply, both scarcity and environmental impacts, and the conditions and consequences of a circular economy for metals, based on the reports of UNEP's International Resource Panel.

About The Course

Metals are ubiquitous – they are all around us – and provide a foundation upon which our economies are built. Economic development is deeply coupled with the use of metals. During the 20th century the production has increased exponentially, and the variety of metal applications in society has grown rapidly. In addition to mass applications such as steel in buildings, copper in wires and aluminium in airplanes, more and more metals are required for innovative technologies such as the use of rare earth elements in renewable energy systems. 

Worldwide, and in particular in emerging economies, the demand for metals is rapidly increasing. The continued increase in metals demand and use over the 20th century has led to substantial social, economic and environmental challenges. Mining activities expand but easily accessible deposits are becoming scarce. As a result, the supply of critical metals is under an increasing pressure. This implies recycling, also referred to as “urban mining”, is of growing importance in generating raw materials. In the end, the only really effective solution to the metals challenge may be to move towards a circular economy. 

To be able to do that, information is needed on metal stocks in society, their size and residence time, as well as on the technologies that are available to recover these metals when the stocks become obsolete. This course, based on the reports of the Global Metals Flows Working Group of UNEP’s International Resource Panel (IRP), investigates the nature of the metals challenge and the conditions and the consequences of the way out: a circular economy for metals.


Dr. Ester van der Voet
Institute of Environmental Sciences
Leiden University

Prof. dr. Thomas E. Graedel
Industrial Ecology at the School of Forestry and Environmental Studies
Yale University

Prof. dr. Markus Reuter
Director - Technology and Product Management

Dr. René Kleijn
Institute of Environmental Sciences
Leiden University

Dr. ir. Erik Offerman
Materials Science and Engineering (Metals Processing, Microstructures and Properties)
Delft University of Technology

Frequently Asked Questions


1. Will I get a certificate or Statement of Accomplishment after completing this class?
Students who successfully complete the class will receive a Statement of Accomplishment signed by the instructor.

2. Do I earn Leiden University credits upon completion of this class?
No. The certificate of completion is not part of a formal qualification from Leiden University.

3. What resources will I need for this class?
The main body of resources – the UNEP IRP reports on metals – is freely available. You can download the reports here.

4. What are the learning outcomes of this course and why should I take it?
By following this course you will gain:

  • Knowledge of the properties of specific metals: at least of copper, aluminum, zinc and lead.
  • Knowledge of anthropogenic stocks and flows of metals.
  • Insights into present and future challenges related to metal supply and demand.
  • Knowledge of environmental impacts related to metal cycles.
  • Insight in requirements for a closed metals loop economy.

5. I don't want to wait this long, what can I do to get started?
Read the four reports on metals that have been published by UNEP's International Resource Panel. These reports can be downloaded here.

6. Why do you offer this course for free?
Leiden University is grounded in a long standing tradition in providing students the space for obtaining a thorough and multifaceted education. This MOOC offers us the possibility to share our knowledge globally.

Recommended Background

No prior background required. Basic chemistry knowledge is helpful.