Cities are an intermediate store for valuable material resources, believes the Danish architect and upcycler Anders Lendager. However, the longevity and potential for reuse of building materials is currently not being exploited. During building reconstruction or demolition, too many materials are still thrown away and disposed of before the end of their useful lifecycle. Not for much longer, if Vienna can have a say in the matter.

13 cities, one goal

It was the beginning of 2019 when Vienna got together with 12 other European cities as part of the Big Buyers Initiative working group on Circular Construction with one mission in mind: improving circularity in the construction sector by promoting procurement of reused, recycled or reusable construction materials and dismantling works.

“This collaboration was the wind under our wings,” says Dr. Anna-Vera Deinhammer, coordinator for the Construction Industry, and program lead for DoTank Circular City Wien 2020-2030, “we strengthened the position of the topic locally and elevated it on a higher strategic level, and we learned from other cities’ experiences making our learning curve faster and better.”

Through exchanges with the cities in the group, Vienna decided to launch a first pilot project aiming to use recycled concrete and insulation material in new buildings to prove how the city could influence the market towards more circular solutions in the construction sector.

Describing the dream

The City of Vienna started its journey towards circularity in the Seestadt Aspern, an urban expansion project within the city’s boundaries, just 15 minutes by subway from the city centre. Thanks to coordination and aligned ambitions in the early planning phases of the development, one million tonnes of excavated earth and aggregates sourced, cleaned and crushed on the site were used in the construction of 3,000 new housing units. Mobile machines ensured that 90% of CO₂ emissions were saved compared to using an aggregate processing plant 25 km away.

But this was landmass coordination is only one aspect of a circular city. Another is planning and constructing buildings with a higher circularity factor. As Vienna plans the construction of a new building in 2020, this is the perfect occasion to showcase the use of recycled concrete and insulation materials. “They needed new buildings and we used the opportunity to suggest implementing recycled concrete and recycled isolation materials,” says Dr. Deinhammer.

How can a municipality influence the market, so it gets what it wants? As the offer of secondary material is limited at the moment, it is important that the city acts as a promoter of innovative solutions through the way it launches its calls and setting a precedent through its own public project. In the spring of 2020, Vienna started developing a tender for the new construction project that includes a list of criteria describing the perfect product.

“For example, we are discussing a minimum amount of gravel made of reused concrete,” explains Dr. Deinhammer “We thinking about indicating a minimum amount or proportion of secondary material use for each component, describing a reference product that represents the ideal offer, the dream.” Aware that they might not get a perfect match, this choice wanted to inspire the market to aim high, as the offer that came closest to the ideal would be selected.

Gathering proof to grow

The results from this first pilot, which will be completed in the summer of 2023, will be used to argue that a more circular approach to the construction sector is a more sustainable one. It is therefore essential that these results be monitored using appropriate measurable environmental impact indicators.

Today, CO2 emissions are the only indicator for environmental impact in the constructor sector, while Vienna intends to include more indicators such as the reduction of natural material extraction, or the indirect reduction of energy use or pollution linked, for example, to transport of construction material.

The pilot has already inspired an additional project tackling a different phase of the construction chain, refurbishment, proving that circularity can and should be applied to all stages of a building’s lifecycle. The WieNeu+ project will oversee the refurbishment of an entire neighbourhood in Vienna, and in this case, it is intended to implement circularity aspects in as many retrofitting actions as possible. For example, harvesting building products and materials from dismantled buildings and re-using them in another construction project.

As an additional step, the city will organise citizens’ outreach via a reused container pop-up office where information and photos from the pilots will be used to explain to citizens how the refurbishment will work and look using secondary materials, and the advantages of this approach. The city especially wants to address the scepticism that some citizens have around the quality of secondary materials. “We have to show and prove that using secondary materials in new buildings or in refurbished ones doesn’t affect the quality of the building,” explains Dr. Deinhammer.

The three Rs: reduce, reuse and recycle

The experience and the results of pilot projects such as these, as well as the exchanges with other European cities within the Big Buyers Initiative, have fed into Vienna’s wider DoTank Circular City Wien 2020-2030 strategy. The city is committed to take the entire construction industry on a journey to reuse in construction and materials management. The final goal of the strategy is to have 80% of components and materials for new buildings , major reconstructions and renovations coming from reused sources, by 2050.

The strategy is based on three principles: reduce, reuse, recycle. The first refers to designing buildings with minimising use of materials in mind. Today, construction materials account for half of raw materials used in Europe. Therefore, lowering the consumption of raw materials means protecting our natural resources, reducing land consumption, preserving biodiversity, and acting responsibly within planetary boundaries.

Buildings should also be designed and constructed so as to be dismantled, separating elements and materials that can be reused as they are, a bit like a game of LEGO. When building materials are successfully reused, energy is saved because the product is used as it is elsewhere, achieving the goal of climate protection by significantly reducing greenhouse gas emissions, and the goal of resource conservation, as no new raw materials need to be mined. “It is important to emphasise that recycling is good, but we also have to start reusing the materials and the products as they are,” says Dr. Deinhammer.

Secondary raw materials should be preferred in construction because they create interesting recycling opportunities and transform buildings into material repositories rather than waste piles – construction and demolition waste represents a third of all waste today, one of the largest waste fractions by volume in the EU. Secondary raw materials can play a big role in designing our habitat to be more resilient and to be prepared for future climatic events caused by climate change, such as heavy rainfall or heatwaves.

In addition, reducing, reusing and recycling will all have a significant impact in greenhouse gas emissions levels. Currently, buildings and construction are responsible for 39% of global carbon emissions, while construction works and materials alone represent 11%. Not to mention the carbon footprint of material extraction, processing, transportation, and construction works. Acting on the construction sector will therefore have an important effect in achieving the European Green Deal goals.

All actors in the chain need to play their part

A construction sector based on circularity means integrating the entire resource cycle of buildings from production to disposal or recycling into a sustainability concept, while avoiding waste and inefficient use of energy. However, the sector is currently not making the necessary connection between programming, planning, and execution to achieve this goal.

“We are not changing the way we build; we need to change the way we approach a construction project,” says Dr. Deinhammer. For example, every construction activity begins with the supply of raw materials, which are further processed and assembled into components, so the decision to prefer a certain construction method will also decide the whole material’s lifecycle.

As the sector involves many actors, such as developers, planners, users and building owners, for a successful approach to circular construction they all need to be involved and play a role in applying the principles of circular economy. “Our key learning is that we need to do this together,” says Dr. Deinhammer “with so many actors all across the value chain, we need to combine municipality with research and, of course, with the market.”

Procurement managers, for example, need an overview of planning and architectural firms that can design integrated construction processes. The Vienna- based architectural start-up materialnomaden, for example, has worked on tangible implementation projects and created pilots and prototypes demonstrating the constructional, architectural and artistic benefit of designing buildings reusing and recycling materials.

In turn, firms like materialnomaden need information on available secondary products. This would be easier if there were a coordinated market for secondary materials. To fill this gap, the IÖB innovation platform in Vienna launched an innovation challenge, calling for businesses to partner up with the city and create a EU-wide marketplace that will allow stakeholders of the construction sector to advertise and sell their relevant services and products.

Finally, to make reuse possible in construction projects, construction and dismantling must be synchronized. These processes can also become an opportunity to address social inclusion, as does the social enterprise BauKarussell in Vienna and other Austrian cities. Through the association people far from the labour market can dismantle and sort building components and material from demolition sites to reuse or to recycle, and their salary is financed through the income from the value of recovered materials.

Cities can lead the change

The industrialised countries’ current standard of living leads to increasing consumption of resources that the earth can no longer cover from primary resources alone. For example, cities make up for more than 75% of resource use, a huge demand that influences the entire surrounding area.

Therefore, cities can play an important part in drastically reducing their material footprint and, at the same time, keeping the resources already used regionally in circulation. Circular Economy as a concept addresses the industrial sector, however it has so far mostly been used in the field of waste management, while it has great potential also in the construction sector.

Cities can lead the way by playing the roles of promoter, through procurement and public projects; enabler, through coordinating partnerships and giving financial support; and as regulator, through establishing permits and zoning rules. As the first pilot in Vienna has shown, cities can inspire the market by being a demanding client and painting the picture they want to see, and maybe the ‘dream’ scenario will soon become reality.

Eurocities and ICLEI are currently running the initiative on behalf of the European Commission, DG Internal Market, Industry Entrepreneurship and SMEs (DG GROW).

For more information and results from the Big Buyers Initiative, visit the project’s website. The group’s work will continue under a new project called the Big Buyers for Climate and Environment. Stay tuned for updates on this exciting new opportunity.