ZIN project in Brussels to set new standard for sustainability

One of the largest urban mining projects in Europe, the 110,000 sq m ZIN building in Brussels, developed by Befimmo, the Belgian REIT, is due to be completed by the end of this year and will set a new benchmark for sustainability.

Urban mining is an innovative approach that sees existing buildings as “mines” of valuable materials that can be extracted, recovered and re-used.

“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,” said Michael Moradiellos del Molino, international head of sustainability and circularity, Drees & Sommer, who supervised the ZIN project. “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.”

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

The ZIN project combines different functions, accommodating residential, offices and a hotel in one building. The multifunctional design of ZIN reflects the transformation happening in the North district, which used to be a business area and has been hit by the pandemic and the working-from-home trend. Now the city authorities aim to revitalisse the area into a more vibrant and greener mixed-use neighbourhood.

The main part of the building, 75,000 sq m, is for office use, 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.

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

The quantity of waste was limited by retaining as many features of the existing building as possible, such as the five underground floors, the foundations and the central cores. All the elements that could not be reused onsite have been recycled or reused elsewhere.

CCB Concrete transformed 30,000 tonnes of old concrete from the original towers into high-quality, circular concrete, which was reused as a full load-bearing floor slab in the ZIN reconstruction. “We tested the concrete and had very good results, so we were confident it could be reused,” said 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.”

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

“We had the towers, we had the materials, we had the idea, we had the technology and the know-how, so we went ahead,” said 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.”