The city is a rich material resource. There is, for example, more copper in buildings than is left in the earth’s crust. In Switzerland, the total copper stock in buildings is 65kg per person. By reusing the materials already deposited in our settlements rather than extracting new raw materials, the rate of material accumulation would slow down and the amount of building materials removed and redeposited as waste would be reduced.
Formally or informally, we already mine the city. In parts of the United States, copper extraction from abandoned and inhabited buildings is so lucrative that police task forces have been formed to combat metal theft. But the institutions needed to effectively mine the city are presently missing. The labor needed to sort and select materials for reuse needs an economic apparatus. Presently, although the labor of erecting new buildings is a crucial part of the economy, demolishing them is often done haphazardly and with a minimum of time and labor.
The concept of mining the cities was elaborated at LafargeHolcim Roundtables in the USA, Switzerland and Germany in preparation for the 6th International LafargeHolcim Forum for Sustainable Construction 2019 in Cairo, Egypt. The events brought together researchers and practitioners from different fields – architects, engineers, historians, material scientists, policy makers, sociologists, and the material industry – to envision a more sustainable future for construction.
As the key input to the Forum, 22 Propositions offers strategies for both the material supply chain and material use in buildings. The propositions aim to “re-materialize” construction by rethinking the building material cycle from extraction to processing, design, transport, installation, maintenance, and removal.
The changes proposed would contribute to a construction industry with a smaller ecological footprint and a shift away from the unsustainable assumption that raw construction uses significant amounts of material. Rethinking materials and material use also has tremendous potential to lower greenhouse gas emissions and reduce dependence on resource extraction.
The Materials Book to be published by Ruby Press Berlin in late 2019 will feature the essence of 22 Propositions as well as a selection of additional proposals to re-materialize construction derived from the findings of the Forum.