London’s iconic Skyline could be the secret formula to unlock Construction’s circular economy in the UK

Europe’s Construction Industry is surpassing the UK with efforts to put in place a circular economy of key waste product: concrete. But the capital holds the key to level the playing field and can lead the way still.

In the heart of the City of London, building firms and sub-contractors are preparing for construction of One Undershaft, which will become the newest landmark in the capital. Beneath the architectural ambition of becoming the tallest building in the city, equalling the height of the Shard, lies a missed opportunity to become a case study for sustainability, and to build a robust circular economy for construction in the capital. The new skyscraper will sit on the site that St Helen’s Tower occupied for more than five decades. To date, this will be the tallest building ever to be demolished in London. Levelling the building will generate approximately 49,000 tonnes of demolished concrete, which we expect to be recycled, but not used, in the construction of One Undershaft. It will also miss the opportunity to permanently remove hundreds of tonnes of CO₂, by converting demolished concrete into carbonated Recycled Concrete Aggregate (cRCA) using neustark’s innovative technology.

Recycling concrete in the UK and in Europe
To be very clear, the UK’s record for recycling demolished concrete is exceptional. Year on year, the UK successfully recycles upwards of 90% of demolished concrete. It is used in many use cases such as in the sub-base of new roads, landscaping, and drainage for underground pipework. The UK is among the leaders in Europe for the total amount of concrete recycled, exceeding the European average (30%), and marginally behind leading countries such as Norway and the Netherlands (95%).

Moving from a recycling economy to a circular economy
While recycling demolished concrete is a fantastic achievement, the construction industry must find a path to return demolished concrete materials back into the fabric of new buildings, moving from a recycling economy and towards a circular economy.

London showed early signs of progress developing its circular economy. In 2006, One Coleman Street (London) adotped recycled materials for the majority of its course aggregates in structural concrete. The following year, the historic Wood Wharf became an early beacon of sustainability using Holcim’s low-carbon concrete ECOPact, made up of 20% recycled materials

Leading European cities have stolen a march on this progress. In Switzerland, the circular economy of construction is thriving, perhaps more than any other city or country in the world. In 2002, a new school building was using 80% of recycled concrete. In 2018, the city’s main art museum, Kunsthaus Zurich, was extended using 98% recycled concrete . Since then, a proportion of the material for a new hospital and several housing complexes reached 95%.

In Munich, the “Bayernkaserne” pilot, due to be completed in 2030, showcases what can be achieved with the right governance and support. The 50-hectare site, a former military barracks, is set to be converted into a thriving new community (district) comprising of 5,500 new homes, a school, office buildings and green spaces. Munich City Council approved an innovative recycling concept, facilitating the process and recycling of all waste material on-site. Processing and recycling 1.2M tonnes of demolished concrete, of which 50% (600K tonnes) will be recycled and reused for the construction of new buildings (on-site).

Principal & Capital cities lead the way
It is no accident that trailblazing examples of building sustainability are found in leading cities across Europe. Innovation (of all types) happens freely in the right eco-system, which includes finance, knowledge, local suporting supply chains and policy support.

The latter, policy support, being the catalyst for pilot projects becoming the ongoing ‘standard’ and encouraging deeper, widespread adoption. In 2005, following the successful completion of Zurich’s first ‘sustainable’ public building (the Im Birch school), city planners and legislators mandated the use of recycled concrete in all new public buildings (a minimum 25% of recycled concrete aggregates must be used). This move was later (2013) expanded to include all new building projects in the city and include the use of low-carbon cement. This progressive policy was the catalyst for the creation of a broad market and innovation in low carbon construction.

The local limitations of circular economies
In a 2019 case study published by the European Commission, Zurich’s sustainable building practices were analysed with guidance for other European Cities. It’s principal successes includes reducing its CO₂ emissions, resulting from the use of fossil fuels, by more than two thirds since 1990. Also, 17,000m3 of recycled concrete aggregate was processed and reused in countless new building projects and renovations between 2005 – 2018. The primary limitation highlighted from Zurich’s progressive approach to recycled concrete was the parameters and reach of the supporting supply chain. The case study observed, from an energy perspective alone, the use of recycled concrete aggregate only makes sense, when it can be sourced within a 25 kilometer (15 mile) radius of the construction site.

Supporting London’s circular economy
London, with an average radius of 27.5km / 17.5miles) is seemingly a near-perfect geographical environment for such a circular economy to emerge. The Greater London Authority (GLA) also provides a supportive policy environment to grow the circular economy in the capital. Policy SI7 of the London Plan (2021) – mandates a ‘Circular Economy Statement’ in all planning applications allowing architects and construction firms to experiment with more recycled concrete aggregate in projects. Although, arguably this tick box exercise, does not go far enough to encourage planners to make the necessary leap of faith.

So what is holding London back? Why will demolished concrete from St Helen’s Tower be recycled over supporting the growth of the circular economy and construction of One Undershaft. Firstly, the established ‘recycling economy’ is strong, maybe too strong. It has undoubtably blocked the ‘circular economy’ from taking shape in London and across the UK more broadly. The second is awareness according to Armin Grieder, the head of engineering at Zurich’s building surveyor’s office. Speaking to Bloomberg in 2021, Grieder said: “The biggest obstacle to a more widespread use of recycled concrete is awareness, some architects, planners and engineers aren’t yet convinced, and believe it requires more of an effort in the building process. That’s not the case, it’s just not standard material, and more people need to understand it better”. This has been proven, in the 2023 Circular Economy report published by the Greater London Authority (GTA), where it cited just 4 projects over the course of the year reaching ‘best practice’ for circularity in planning and construction.

Quantifying the missed opportunity
Applying Zurich’s pilot (school) example from 2002, using 80% of recycled concrete with a (recycled aggregate) subsititution rate of 45%, to the most recent addition to London’s skyline, One Undershaft, we can quantify the ‘missed opportunity’ more clearly. 23,256 tonnes of recycled concrete aggregate could be used to develop high strength (C40) concrete, to be used in the construct of One Undershaft, almost a half (47%) of the demolished concrete removed from St Helen’s Tower (49,000 tonnes). Of course, there are countless other environmental benefits for adopting the circular economy, such as avoiding the creation and transportation of the same quantity of virgin aggregate and the CO₂ that process would produce. With neustark’s mineralization technology, a further 232 tonnes of CO₂ can be permanently stored in London’s newest landmark building, and other buildings across the capital.

Multiply these benefits across London’s ever-growing pipeline of major regeneration projects and it becomes clear how London can become the catalyst for real change across the UK. It is also clear how recycling demolished concrete is potentially holding back the industry from prioritising of the circular economy, preventing this important supply chain from being established. The circular economy simply must grow in all industries - but construction / concrete must develop quicker than most given its current environmental impact. The examples across Europe (Switzerland and Germany) have shown the way. Innovations such as neustark’s mineralisation technology (now deployed in London), has made it even easier for contruction firms to lower their CO₂ impact. Today, the opportunity to avoid, and permanently store thousands of tonnes of carbon is being left on the architect’s drawing board.