"Keep as many materials as possible in circulation"

This interview was first published in topos, July 2026. The question came from Katharina Kohring.

Urban mining is often cited as a key strategy for a sustainable supply of raw materials. What exactly is meant by urban mining, and why is the concept currently gaining so much prominence?

Urban mining views our infrastructure, buildings and technical installations, durable goods and landfill sites as potential sources of a wide variety of materials. This is also referred to as an anthropogenic material stock. These include, for example, mineral building materials such as concrete, as well as various metals, plastics and wood. When, for example, buildings are deconstructed – that is, demolished – many of these materials have hitherto been treated as waste and may require costly disposal. At the same time, according to the Global Resources Outlook 2025 by the United Nations International Resource Panel, the extraction and processing of primary raw materials – that is, raw materials from natural deposits – and the associated environmental impacts are a major cause of the three global crises: biodiversity loss, climate change and environmental pollution. Urban mining, ideally as part of a circular economy in which materials and raw materials are kept in circulation for as long as possible, therefore offers great opportunities to counteract these crises. The first important step in urban mining is to identify existing materials, their available quantities and the possibilities for recovery. To this end, cities and local authorities, for example, create so-called urban mining registers in which the potential for each building is assessed. 

Cities are increasingly seen as ‘reservoirs of raw materials’. In your view, which materials and material flows are of particular focus when discussing urban mining?

In principle, for an initial assessment, one can simply look around the room or out of the window: it can be assumed that most buildings, as well as infrastructure such as roads or utility lines, will sooner or later be converted, renovated or demolished. Ideally, as many of the resulting materials as possible would be used as high-quality secondary raw materials, meaning the materials should be reused in their original or an equivalent function. Particularly relevant material flows here are the before mentioned mineral building materials, metals and plastics, as well as wood. But the high-quality reuse of the window glass that perhaps just caught your eye could also take the form of melted-down shards in new window glass or as a cut-to-size pane in a new window. In my view, the focus here lies on mineral building materials such as concrete or plaster, particularly given the large quantities involved and the fact that recycling loops are not yet sufficiently established. 

Many materials in buildings or infrastructure are tightly bonded together or contaminated. What proportion of these materials can realistically be recovered to a high standard?

Although this depends largely on how the materials are installed, it is technically possible to divert the majority of materials in buildings and infrastructure to high-quality secondary use. This situation is also improving continuously, as the potential for repurposing and dismantling is increasingly being taken into account right from the planning stage. Furthermore, so-called selective dismantling – whereby individual layers of building components are separated and removed one after the other as far as possible, thereby yielding materials of a single type – is becoming increasingly common practice. Furthermore, better processing methods are being developed and legal, administrative or organisational challenges – such as unclear requirements regarding traceability and safety, contamination with pollutants or a lack of information sharing on available components and materials – are being addressed, as demonstrated in the fourteen research projects under the FONA funding scheme ‘Resource-efficient circular economy – Urban mining: Tapping anthropogenic deposits as a source of raw materials’ funded by the BMFTR (Bundesministerium für Forschung, Technologie und Raumfahrt).

Urban mining is often portrayed as environmentally beneficial. Are there also cases where demolition, sorting and processing consume more energy or resources than the use of new raw materials?

There are indeed cases where the processing of materials can be said to have a greater environmental impact than the extraction of primary raw materials, as well as unavoidable waste – often, for example, in the case of the coatings mentioned earlier – and this is likely to continue. The aim of urban mining is to utilise as high a proportion as possible of the materials in the anthropogenic material stock. At the same time, the environmental assessment depends heavily on the material in question, how it is used, and which criteria are applied – for example, how the destruction of landscapes worthy of protection through primary raw material extraction is assessed. In principle, the reuse and recycling of materials, and thus the reduction in the demand for primary raw materials, is considered environmentally beneficial.

Another issue appears to be economic viability. Under what market conditions is urban mining actually worthwhile – and where does the concept reach its economic limits?

Under current market conditions, secondary materials are indeed often less cost-effective than competing primary materials. However, the relative price advantages of primary materials are often only achievable because environmental and social costs are not taken into account. But even low-cost alternative disposal methods, such as landfill and sham recycling abroad, can compete with recycling. As soon as these are factored into the costs of producing primary materials – for example, through carbon pricing – or are subject to legal restrictions, secondary materials will also become more economically attractive. Furthermore, urban mining can help reduce dependence on raw material imports, the prices of which may fluctuate significantly.

It is particularly in the existing building stock that large quantities of materials remain tied up for decades or even centuries. Does this not mean that urban mining, as a source of raw materials, becomes available with a significant time lag, thereby making accurate planning using these very materials virtually impossible?

Although the materials remain tied up in buildings for a long time, construction projects, as well as refurbishment or demolition projects, do not generally take place unexpectedly. In addition to recording the anthropogenic material stock in urban mining registers, approaches are currently being developed to link planned conversion or demolition projects with upcoming new-build projects at a regional level wherever possible, in order to reuse the resulting materials – and ideally entire building components – as directly as possible. Further challenges, as already mentioned, include the transfer of information, processing and temporary storage, as well as any security concerns or legal obstacles that may arise.

What role can it realistically play in the long term in the supply of raw materials – and what problems will it probably not be able to solve?

Overall, there will not be enough secondary material available in the foreseeable future to meet current material demand in the construction sector – instead, the anthropogenic material stock continues to grow. The initial aim must therefore be to keep as many materials as possible in circulation rather than disposing of them, whilst simultaneously reducing overall material demand.

Are there already any cities, projects or examples that, in your view, demonstrate how urban mining can be successfully implemented? What lessons can be learnt from them?

A well-known example is the new Korbach Town Hall: the mineral demolition materials from the 1970s extension that was demolished were processed locally and reused in the new building. In addition, the planning and construction of the new building took into account, right from the start, the need for the structure to be as easily dismantled as possible. This and other projects demonstrate that local urban mining is feasible in practice, provided it is an integral part of the planning process.

Julia Schütz has been working as a researcher in the Resources & Transport division at the Oeko-Institut from spring 2023 to June 2026. As an environmental engineer, she is currently working on the key areas of the resource transition, life-cycle assessment of recycling processes, corporate carbon footprinting, and sustainable sporting events. Prior to joining the Oeko-Institut, she worked as a project engineer advising planning teams on sustainable building certification for various construction projects.