What is the impact of circular construction?

The construction sector is one of the largest producers of waste. This waste is largely recycled, but we could find much smarter ways of dealing with it, say TNO’s Sanne van Leeuwen and Suzanne de Vos. They are linking partners throughout the construction chain – as well as housing corporations and local authorities – into networks to tackle this problem. It then becomes clear that the higher quality recycling of construction waste can deliver still greater environmental benefits.

Sand, concrete, glass, brick, wood, steel – the construction industry accounts for half of all the materials consumed in the Netherlands. In addition, the production of building materials contributes significantly to COemissions, according to the TNO publication entitled ‘Circular construction that has an impact’. Accordingly, Suzanne de Vos – TNO’s Sustainability Consultant – feels it is appropriate to help the construction sector reduce its environmental impact. One way to do this is by approaching construction material flows from a circular viewpoint, treating them not as waste, but as high-quality raw materials for new applications. “Despite the construction industry’s past efforts to process waste as efficiently as possible, we are convinced that recycling construction waste for higher quality uses will bring greater environmental benefits. The same applies to intensifying our efforts in the maintenance area and to extending the service life of structures and materials.” The entire construction chain largely takes place within the borders of the Netherlands. This brings the goal of realizing circular aspirations within reach.

“There’s more than one way to build a wall. For example, you could use mortarless bricks that you just click together”


The processing of hardwood is a good example. Any wood stripped from buildings during renovation or demolition work usually ends up in open containers, where it is exposed to damp. This reduces the chances of reusing it in a way that reflects its true value. “All this material is disposed of as a single type of waste, made up of wood of all kinds, sizes and qualities. Sadly, because of this, a lot of wood ends up in the incinerator”, says Sanne van Leeuwen, Project Manager at TNO’s Innovation Centre for Building. Although companies are obliged to sort different material flows separately, their main concerns are how to transport and process them as conveniently as possible, rather than how to reuse them. In the case of wood, especially high-grade hardwood, dry transport and storage is essential. “Next, in essence, it is only a question of sanding the wood down and using it as new shelves elsewhere.”


This requires a different method of waste collection, a different type of logistic organization, and a switch of roles – in which waste processors also become suppliers. Sanne van Leeuwen explains that “In this way, we are trying to set up a new process. In the beginning, there is a certain amount of trial and error involved. But, when the parties involved are brought together, they soon begin to see that things could, indeed, be done differently! That is when change happens.”

“For example, we bring housing corporations together with suppliers of window frames and with wood processing companies”


Even in the case of bricks, there are circular alternatives. At the moment, masonry rubble and other stony rubble often ends up as foundation layers for new roads. However, the supply of material for this purpose is expected to far outstrip demand. “That’s not the only way to build walls”, says Ms De Vos. “For example, you could use mortarless bricks that just click together. We have also worked with a brick supplier to see whether it is possible to separate masonry rubble into mortar and clean bricks at low kiln temperatures. This is just the kind of knowledge we very are keen to develop, in cooperation with companies.”


In addition to bringing together construction companies from the various material chains, TNO also links them to organizations with large building volumes, such as housing corporations and infrastructure operators. Suzanne de Vos points out that “For example, we bring housing corporations together with suppliers of window frames and with wood processing companies. We are also supplying data on all of the materials in the built environment. We created an interactive map showing which building materials are being used in the Netherlands, where and when secondary materials are becoming available, how the supply side is developing, and where demand for new raw materials is being generated. In this way, we can identify opportunities for bringing together partners from various parts of the chain.”

“We help local authorities to translate aspirations into clear indicators, such as reducing COemissions or boosting employment”


The promotion of circular construction is not limited to construction companies or property owners alone. Local authorities can also play a part. For example, the local authority at Assen set itself the ambitious goal of building one hundred ‘circular houses’ in the upcoming years. TNO looked into ways in which Assen could achieve this goal. It developed scenarios for three different areas: outside the city limits, in the inner city, or on an industrial estate.

Jesse Siegers, policy advisor at the Assen local authority, found TNO’s study very valuable. “Our initial aspirations were quite general in nature. But we are better able to weigh up the various options, now we know what the different scenarios offer in terms of COemissions, environmental costs, material costs, knowledge development, house prices and employment.” According to TNO’s Suzanne de Vos, it is vital for aspirations like this to be measurable. “That enables you to proceed in a much more focused way. We help local authorities to translate these aspirations into clear indicators, such as reducing CO2emissions or boosting employment. Our work involves quantifying the environmental and economic impacts involved, which is why we often say ‘we add the facts’.


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