How Brussels is leading the way in urban mining

Brussels urban mining
The ZIN building in Brussels used urban mining principles. More than 1,000 tonnes of materials were reused and modular components mean it can be adapted for changing needs in future

Two pioneering projects show how this innovative approach can transform waste materials into useful resources.

Belgium used to be famous for its mining industry, but now Brussels is leading the way in a new and far more environmentally friendly field: urban mining. It’s an innovative approach that sees existing buildings as ‘mines’ of valuable materials that can be extracted, recovered and reused. Reintegrating these resources into the production cycle promotes a more sustainable and resource-efficient economy.

The demolition of buildings is the largest source of waste in Europe. Currently, most building materials either end up in landfills, where they are destroyed, or downcycled into products of much lower value. Both result in a significant loss of valuable resources.

Out of sight, out of mind is no longer an acceptable attitude to waste, given finite resources and the growing pressures of urbanisation and increasing populations. It is predicted that global demand for materials will triple by 2050. In the European Union alone, more than 450 million tonnes of construction and demolition waste are generated every year.

“Urban mining is a response to non-circular construction methods in decades past, and seeks to transform waste materials into resources to be kept in use for as long as possible,” explains Michael Moradiellos del Molino, international head of sustainability and circularity at consultant Drees & Sommer. “We need to move away from the mindset of demolition and instead identify and review the existing materials in our buildings, as in our cities we are surrounded by more than 50 billion tonnes of valuable materials.”

Now Brussels is reaping the benefits of its ambitious vision. In 2019, the Brussels-Capital Region adopted circular economy policies. Demolition in the region is not allowed unless there is an urban mining plan and new building must follow the ‘design for disassembly’ principle.

The ZIN project

The ZIN project in Brussels is one of the largest urban mining projects in Europe. Developed by Befimmo, the Belgian REIT, it spans more than 110,000 sq m and is set to be completed by the end of 2024.

The project involves the renovation of towers 1 and 2 of what was the Brussels Trade Centre in the North area of the city, which is currently undergoing major regeneration. After the dismantling process, the existing towers were joined by a new section designed by Jaspers Eyers Architects. This section is 100m high with 14 double-height floors.

The ZIN project combines different functions, accommodating residential, offices and a hotel in one building. This multifunctional design reflects the transformation happening in the North district. Once a business area that was deserted in the evenings, it was then hit by the pandemic and the working-from-home trend. Now the city authorities are aiming to revitalise the area into a more vibrant and greener mixed-use neighbourhood.

The main part of the ZIN building, 75,000 sq m, is for office space, including a co-working area. Most of the space has been leased by the Flemish government since February 2024. A further 14,000 sq m is for apartments and 16,000 sq m for hotel accommodation, leisure areas, restaurants and shops.

“We’re determined to reshape the industry, with sustainability at the centre of everything we do, and we strive to set new standards that go beyond the expected,” says Wim Plaum, project director at Befimmo. “We focus on reusing materials onsite through urban mining, ensuring every project feeds into a circular economy. Working closely with partners and subcontractors, this is how we create a future that is sustainable, practical and responsible.”

Urban mining in action

The ZIN project shows urban mining in action, with the inventory and reuse of as many materials as possible. More than 1,000 tonnes of materials, including raised floors, partition walls, insulation and roof tiles, have been reused, and 140 tonnes were upcycled.

The first step was the inventory: more than 400 materials were analysed over a year in an operation known as curage, supervised by Drees & Sommer, to ascertain whether they could be retained, reused in the project, or recycled for use elsewhere. The flint slabs of the building’s former plinth, for example, were reused to cover the new terraces.

Brussels urban mining ZIN building
Natural foliage features inside the the ZIN building in Brussels

The quantity of waste was limited by retaining as many features of the existing building as possible, including the five underground floors, the foundations and the central cores.

CCB Concrete transformed 30,000 tonnes of rubble from the original towers into high-grade concrete, which was reused as a full load-bearing floor slab in the ZIN reconstruction.

“We tested the concrete and got very good results, so we were confident it could be reused,” says Moradiellos del Molino. “It was a trial-and-error process with a lot of experiments and not all of them worked. But the idea is that others will follow our example.”

Adaptable space

Circularity was incorporated in the building’s design, extending its life by making it easily adaptable to changing needs in future. The basic structure is designed to stay the same, but all components can be disassembled so space can be adapted to new functions, with the exception of the structural floors.

The facade, for example, is made from modular prefab components which were ‘clicked’ into place and can be easily disassembled if needed. There are no fixed concrete slabs, making it easy to increase the residential component. For this reason, all floors have terraces, including those currently used as offices.

“We had the towers, we had the materials, we had the idea, we had the technology and the knowhow, so we went ahead,” adds Moradiellos del Molino. “Urban mining is never cheaper than buying new materials, but we wanted to challenge the market and show that it can be done.”

The Multi Tower

Another example of the positive impact the city government’s circular economy policies have had is the Multi Tower in the centre of Brussels. It is the first CO2-neutral office building in the Belgian capital.

The tower is a 19-storey project developed by Immobel and Whitewood, which acquired the building in 2015. Following renovation, the building now provides 44,000 sq m of office space accommodating 2,000 people, along with retail units. The project has earned BREEAM Excellent certification, placing it among the top 10% of new commercial buildings in Belgium.

The idea was to give a second life to the H-shaped Brouckère tower, built in the 1960s, retaining the three-storey base to create a new, flexible office building combined with public spaces overlooking what is now a pedestrian boulevard.

Brussels urban mining Multi Tower
Multi Tower has the highest percentage of reused materials among large-scale office projects in Brussels, with 3% sourced through urban mining of iconic Belgian locations

Urban mining played a big role in the renovation of the Multi Tower. A total of 89% of the existing concrete was reused, saving 3,259 tonnes of embodied carbon, 20,000 tonnes of waste, 2,222 cement trucks and 2,000 cement truck journeys.

The building has the highest percentage of reused materials among large-scale office projects in Brussels, with 3% sourced through urban mining of iconic Belgian locations, in cooperation with circularity partner Rotor DC. The Jules Wabbes hexagonal tiles in the lobby, for example, were sourced from old BeBank offices.

“This has been a milestone project for Brussels and for the sector, nothing on this scale had ever been attempted,” says Frederik Jacobs, chief executive of Conix RDBM Architects, who has overseen the renovation project. “When we first decided to reuse materials from this and other buildings, everyone was shocked and didn’t think it could work, but we knew it was the future.”

As the street had been pedestrianised, the architects decided to open up the lobby and remove the ramps to the carpark below, adding extra space. The materials taken away were reused to build the extension, and the new materials can be reused in the future. The vast lobby is now open to the public and staircases lead up to the third floor terraces with gardens.

Opportunity to experiment

“It is always more expensive and more time-consuming to reuse old materials, and you can find unexpected problems like asbestos, but we were fortunate to have owners who had the vision and gave us the opportunity to experiment and do something new,” says Jacobs.

“The transformation of the Multi Tower is a testament to our commitment to sustainability, circularity and innovation,” says Valérie Vermandel, chief development officer at Whitewood. “By turning what was once a dark, heavy structure into a bright, multi-functional workspace, we have not only revitalised the building, but set a new standard for urban development.”

Brussels urban mining Multi Tower
At the Multi Tower, the architects decided to open up the lobby and remove the ramps to the carpark below, adding extra space

There was also a practical element to the decision, given the length of time it takes to get a building permit and the change in the authorities’ outlook on high-rise developments in the city centre. “If we had demolished the building we would never have got permission to build something of this size again,” explains Vermandel.

In the urban mining process it is crucial to be flexible, Jacobs says, as the materials supply chain will inevitably change. “It is not one decision, but a long series of decisions you have to take along the way. There is a lot of box-ticking to be done, but technology makes managing the process much easier.”

Thanks to its energy and carbon performance, as well as circular economy credentials, the French group Total Energies, Bpost, Belgium’s leading postal operator and Immobel, the oldest real estate company in the country, have chosen to become tenants in the building. Immobel has stopped doing new builds and committed to only do renovations.

In the loop: what the circular economy means for you

Both the ZIN and the Multi Tower urban mining projects in Brussels have been supervised by the Environmental Protection Encouragement Agency (EPEA). Founded in 1987 in Hamburg
by Michael Braungart, the organisation has established the Cradle to Cradle (C2C) principle as a method for the circular economy in all industrial sectors, as well as in the construction and real estate industries.

“The circular economy must be restorative and regenerative by design,” says Hein van Tuijl, managing director of EPEA Benelux. “It means doing the right thing with the right materials. In these buildings all new materials have C2C certifications.”

For the Brussels developments, as in other building projects, EPEA has analysed the material value of existing portfolios, developed urban mining concepts and brought materials back into circulation through its industrial reuse network of product manufacturers.

Flexible, reusable buildings

Buildings based on the C2C design principle are intended to be flexible and reusable. The healthy materials built and selected are easy to dismantle, can be separated by type and are therefore completely recyclable. This turns buildings into long-lasting and valuable raw material deposits, which release the resources again after the end of their useful life and thus, contribute to maintaining the value of the property.

“We know that the future of construction is not just about putting one brick on top of another but it’s about doing it better for the people, and for the planet that supports us all,” says Wim Plaum, project director at Belgian property management company Befimmo. “By working closely with our partners and subcontractors, we challenge them to achieve Cradle-to-Cradle certification, because real progress comes when we all move in the same direction.”

Each building receives a circularity passport as a tool for architects, designers, builders and contractors. The passport provides detailed information about which materials have been used, which materials can be easily separated and recycled and the chemical composition of the installed products. It also evaluates the carbon footprint, including the “grey energy” from the production, transport, deconstruction, and disposal of building materials, providing a comprehensive lifecycle assessment.

Analysing data collected

This information not only makes it easy to determine the value of the structures installed in buildings, it can also be used for financing purposes, risk assessments and appraisals. All data collected by EPEA and recorded in the passport can be analysed and shared via its digital platform and are stored until the end of a property’s life, allowing owners to know exactly which materials can be recovered in the event of demolition. “You cannot recycle properly if you don’t know what materials you are dealing with,” notes van Tuijl.

Since the inception of the EU-funded research project Buildings As Material Banks in 2015, EPEA has issued more than 100 circularity passports.

EPEA’s industrial reuse approach differs from traditional recycling, which often includes downcycling or energy recovery methods that are detrimental to climate protection and resource conservation.

 “Beyond the obvious ecological perks, considering the built environment as a repository of resources can save money and improve health”, said van Tuijl. “Circularity passports provide detailed information on each material’s chemical composition, enabling the use of non-toxic materials in construction and eliminating health risks at the material sifting stage.”

Hazardous chemicals

One example shows what that means. A cycle lane in Zwolle, in the Netherlands, was the world’s first made entirely from recycled plastic bottles, cups and packaging. But what at first glance looks like a great environmentally friendly asset is actually highly damaging to the air and to people’s health.

“The microplastics in the recycled plastic will disperse in the air with the attrition from bicycle wheels, and that is really bad for the environment,” explains van Tuijl. “There is very little awareness of chemical safety and of the presence of hazardous chemicals in recycled materials.”

The circular economy principle is that there is no waste in the conventional sense but only reusable nutrients. Non-durable consumer goods are biodegradable and return to the natural nutrient cycle. Durable consumer goods are broken down into separate raw materials after use and returned to a technical cycle. The quality of materials is retained, all ingredients are chemically safe and recyclable and downcycling is avoided.

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