Urban mining: 'link demolition to the design of a structure'

The construction and infrastructure sector is known as one of the largest producers of waste, while it is also one of the largest consumers of raw materials in the Netherlands. Not to mention greenhouse gas emissions. It’s not a pretty picture when it comes to environmental impact. “In addition to the environmental arguments, there are now also an increasing number of economic arguments for embracing circular construction. Think of improving raw material security,” says Marc van den Berg, assistant professor of circular construction process management at the University of Twente (UT).

In his career, he focuses on developing circular future prospects for the construction industry, with urban mining as a key component. “Urban mining is the harvesting of materials from the existing built environment, with the goal of reusing them elsewhere. I try to link the end of a building’s or infrastructure’s life cycle to its beginning. So I connect the design with the demolition.” This connection wasn’t made before. “They were always two separate worlds, but for a circular future, that connection is crucial.”

A relatively new movement

It’s only been in the last ten years or so that more research has been conducted into this new form of construction. That’s why urban mining is one of the key themes for 4TU.Built Environment. Within the partnership between the construction-related faculties of the four technical universities, there are six core teams, also known as Domain Acceleration Teams (DAT). One of these focuses on circularity and sustainability. Daan Schraven, associate professor in the Faculty of Architecture at TU Delft, is also part of the team and focuses his research primarily on the new economy of the built environment. “For me, urban mining is the process of extracting unused materials or entire spaces to reuse them elsewhere.”

Reuse or recycling

Van den Berg notes that there is a clear difference between reuse and recycling. “In reuse, a specific material or product is reapplied in more or less the same function. Consider, for example, a hollow-core slab (large concrete slabs, ed.) that serves as a floor again at a different location. In recycling, the product is broken down into its raw materials, after which a new product is made from them. Such a hollow-core slab, for example, is ground up and the concrete aggregate is used in the construction of new roads.”

In addition to hollow-core slabs, facade elements, beams, clinker bricks, paving stones, light poles, and streetlights can also be reused. “These examples come primarily from pilot projects we’re currently carrying out in collaboration with companies. It’s not yet common practice to do this on a large scale.” Van den Berg is now focusing primarily on the reuse of products. “That still happens relatively rarely in the Netherlands, so there are significant opportunities here.”

Digitization in demolition

But such a task—including the necessary technology, process changes, and behavioral shifts—cannot be accomplished overnight. Step by step, researchers are now working toward a more circular construction sector. Van den Berg cites the PACER research project as a key link. In this project, various parties are collaborating to investigate how renovations can be carried out in a circular and emission-free manner. “We’re focusing in particular on the digitization of demolition,” he says. “Reusing a material isn’t an isolated activity; it’s part of an entire construction process in which different parties carry out various activities.” Digital information helps identify and reuse materials.

The logistical challenge

There are also several steps to go through between harvesting and reusing the materials. That’s what the RE:Match.D project is all about. The project focuses on the reuse of materials in infrastructure, with a particular emphasis on logistical solutions for transporting materials from the donor (the old infrastructure) to the destination (the new construction site). “A local hub serving as an intermediate station, for example, could be a good solution,” says Van den Berg.

Aspects such as public perception also play a major role here. “What do people find acceptable? Is it acceptable if the paving stones on a new street have chewing gum from the previous street on them? There’s nothing wrong with the quality, but it looks different,” explains the researcher. Currently, they are exploring a rating system to indicate the quality of reusable materials, for example, based on a scale from A through D—where A is brand-new and D has significant damage. Each grade also comes with a different price tag. Van den Berg: “This allows you to weigh the price-quality ratio for each situation and ultimately give as many materials as possible a new lease on life.”

For this project, the university is collaborating with various municipalities in the Twente region. “Currently, municipalities often don’t know which materials are available in other municipalities. We’re trying to connect them.” In the future, Van den Berg wants to see more hubs throughout the country that also communicate effectively with one another to ensure the materials are utilized as effectively as possible.

Better oversight and collaboration are essential

Schraven mentions a subproject of the “Future-Proof Living Environment – Infrastructure” program in which municipalities play a role. This study examines how municipalities can reuse materials from area development projects. Examples include benches, trash cans, and sidewalk pavers that need to be removed from one location but can be reused elsewhere within the municipality. “To make that happen, different departments within the municipalities—as well as the companies involved—must collaborate effectively. This ranges from procurement to planning and from the engineering firm to logistics and the contractor,” explains Schraven. “This way, the parties involved can also see where each other’s opportunities and challenges lie. Ultimately, that leads to better collaboration.”

Economically viable

Ultimately, his goal is for such processes not just to run smoothly once within a municipality, but for them to be reproducible. “It must be possible to implement it multiple times in a row within a municipality, but other municipalities must also be able to adopt it eventually,” he explains. According to the researcher, it is important that a process for reusing materials ultimately becomes economically viable. “It must ultimately pay for itself. Then other parties will also become more interested, and it can have a large-scale impact.”

Scientific studies show that there are certainly opportunities for greater circularity in the construction industry. “Now we need to focus on scaling up,” says Van den Berg. “To do this, it’s important to examine how we can get all parties to work according to the new standardized method. This, in turn, requires further research. That will clarify what conditions are necessary to make it happen.”

Opportunities for education

In addition to research, Schraven also views collaboration in the field of education as a key priority. “Together, we can strengthen education—not only with universities but also in collaboration with universities of applied sciences. Ultimately, the vision must also be implemented in professional practice.” According to the researcher, this will also require people with degrees from universities of applied sciences and vocational schools. “Together, we are working toward a mature circular construction sector.”