We want to make construction circular. But construction is growing and at the same time we are renovating more and demolishing less. Jan Willem van de Groep points out that in such a system you can never close the cycle, that simply follows from material physics. The discussion must therefore be shifted, he believes.
Recently, the Economic Institute for Construction and Structural commissioned by Rijkswaterstaat and RVO published an extensive study on material flows, MKI and CO2-emissions in construction and infrastructure in 2023, including a look ahead to 2030 and 2050. For the first time, this provides a coherent picture of how large the physical flows in both infra and construction really are and how they are expected to develop under common growth scenarios.
The study shows that construction is among the largest consumers of materials in the Netherlands. In infra, asphalt, concrete and granular streams dominate, and in construction, concrete, steel and ceramic products are dominant in terms of both mass and environmental pressure. At the same time, it can be seen that a significant proportion of released materials are being reused and that asphalt recycling is even organized particularly efficiently from an international perspective.
Looking beyond recycling rates and theoretical matches between supply and demand, however, one sees a more fundamental tension that is not technical but physical in nature. Namely, that the Dutch construction sector is growing net and thus structurally taking in more material than is released via demolition, making the system by definition absorbent and closed material cycles at the sector level mathematically impossible as long as the stock continues to increase.
In construction, this tension is exacerbated by a double squeeze. On the one hand, the housing and utility stock continues to grow, so the demand for primary materials exceeds the supply from demolition. On the other hand, social and climate logic dictates that we should demolish less and renovate, transform, top up and extend more. From a sustainability point of view, this makes sense, but at the same time it means that the already limited demolition flow is further diminished and the availability of secondary materials is reduced not only in relative but also in absolute terms.
This creates a paradox that is rarely explicitly named: the more successful we are in preventing demolition, the smaller the secondary material base on which the circular story in new construction rests.
Infra, too, turns out to be less autonomous than is often thought. For although asphalt is highly recycled, the sector is largely dependent on debris flows from building demolition for granular applications. Thus, a decline in construction demolition volumes also indirectly puts pressure on the secondary raw material base for infrastructure, making alternatives mostly primary. The material flow study thus makes it clear that circularity is not just a matter of better separation, smarter contracts or more efficient recycling facilities. Primarily, it is constrained by volume ratios between inflow and outflow, where in a growth scenario, inflow is structurally greater than outflow and so dependence on primary materials persists.
At the same time, the study shows that the dominant environmental pressure in construction comes from structural materials such as concrete and steel. Optimization of recycling rates therefore has limited effect as long as new buildings are constructed largely from impact-intensive primary materials and absolute building production remains high.
The conclusion that construction in a growing system can never become fully circular is therefore not a normative statement but an observation arising from material physics. That is precisely why it is relevant to shift the discussion from the promise of closed cycles to the question of how, within an open, growing system, we can drastically reduce the material footprint per square meter added. The way out then lies not in the pursuit of a perfect cycle, but in a combination of fundamental strategies in which material reduction is central by using fewer kilograms per square meter and longevity and adaptivity are used as core design principles. In this way, buildings can move with generations without demolition, and the inevitable primary inflow shifts to renewable and low-impact materials that not only make the system less stressful but in many cases regenerative by sequestering carbon long term.
If we no longer define circularity as the complete closure of the cycle, but as the organization of a building practice that can also operate within planetary boundaries when growing, a fairer and strategically stronger story will emerge that is more in line with the reality of the Dutch building task. Speed and affordability can only be credibly combined with future-proofing if we dare to face the volume logic of material flows. That is less comfortable than the circular ideal image, but ultimately more consistent with the facts and with the responsibility that the sector bears.
This article was written by Jan Willem van de Groep, program maker, future thinker and publicist. Among other things, he is known for the government program Building Balance. In his column Sights, he gives his views on the big picture in construction.
