Material in Transformation

What remains after waste is burned?

Slag is not an endpoint, but a starting point. It forms during the incineration of municipal waste and consists of a complex mixture of mineral materials. Organic components are lost as gas—what remains is a chemically stable material that is far from insignificant.

In Berlin, hundreds of thousands of tons of waste are thermally treated each year. While the volume is drastically reduced, the materials do not disappear—they are transformed. Metals are recovered, mineral fractions can be used in construction, and other substances remain bound and require long-term management.

The exhibition Slag explores this tension:
between resource and residue, between use and impact.

At its core is the question of how chemistry can enable a circular economy. Instead of treating materials as waste, their composition and properties are reconsidered. What is slag made of? What potential does it hold? And where are its limits?

The materials and projects presented in the exhibition show how residues can become resources—and how chemical innovation contributes to closing material cycles.