Updating the cycle for construction
Moving up the waste hierarchy is crucial for construction products, say members of the IOM3 Construction Materials Group Leadership Team.
It is becoming increasingly essential for organisations within the construction products sector to consider sustainability – clients are asking more questions about such credentials.
The circular economy agenda is of particular interest. It has been picked up by the European Commission as having the potential to create jobs and to derisk some of the supply chain, by making more of what we have available locally in existing buildings.
The UK Government has also put in place a task force group to develop a circular economy strategy for the UK, of which IOM3 CEO Colin Church CEnv FIMMM is a member.
This article gives an overview of the current situation in the UK, but also reflects on initiatives from other countries and examples of best practice from some specific materials.
Upcycling mineral wastes
According to the European Commission, construction and demolition waste (CDW) constitutes more than 30% of all annual waste generated in the UK and EU. Including the UK, EU and USA, this amounts to approximately 140-170Mt, 450-500Mt and 500-600Mt, respectively. Although the CDW recovery rate has gradually increased over the past-two decades to an average of 89%, it varies between countries, ranging from less than 10 to 90%.
Most European countries, including the UK, have ambitious recycling goals, of between 50-90%. In countries like the UK, Netherlands, Germany and Denmark, landfilling has already become more expensive than recycling.
There is therefore a significant need for the recovery, reuse and upcycling of CDW, and the demand for these practices is growing as a viable alternative to using virgin materials, helping to conserve natural resources.
Preserving pristine non-renewable natural resources, as well as reducing carbon emissions through intense processing and manufacturing, are highlighted by initiatives such as the Strategic Research and Innovation Agenda developed within the European Partnership Process4Planet (P4Planet).
Upcycling CDW in particular is a critical topic in built environment research today. Upcycling uses a waste material to create a product of higher quality or value than the original.
'CDW-originating mineral wastes can be typically rich in silicon dioxide, aluminium oxide, calcium oxide, magnesium oxide and iron oxide – a chemical composition that is similar to the ‘traditional’ manufactured construction materials and hence present a compelling opportunity for utilization and upcycling in cementitious materials,' says Dr Antonios Kanellopoulos MIMMM, Associate Professor of Innovative Construction Materials at the University of Hertfordshire. 'These wastes can serve as alternative materials in clinkering, supplementary cementitious materials (SCMs), or as precursors in chemically activated cement.'
He stresses that 'traditional SCMs face significant challenges regarding their continuous availability, often due to originating industrial processes being decommissioned (e.g. fly ash, produced by coal-fired powered stations, is no longer active in the UK since September 2024) as waste or secondary raw materials.
'This highlights the urgent need to transition to new types of cementitious materials, thereby justifying the exploration and accelerated use of alternative sources, prioritising the ‘urban mining’ and circular economy principles.'
Kanellopoulos continues, “Implementing circularity frameworks to upcycle mineral waste can lead to substantial improvements. Recent reports estimate the market growth potential to be between £67bln-92bln.”
For the concrete and cement sector, it will be essential to develop a range of solutions and avoid focusing on single products to circumvent the risk of: (1) shortage of the upcyclable waste and (2) dramatically changing the economy of the industry producing such a waste (and of the waste itself).
Successful upcycled waste materials, like ground granulated blast-furnace slag (GGBS), change the economy of the industry that produces such waste. For example, it might be more profitable selling the waste than the primary product, and, if the waste resource is limited, lead to an economy based on an exponential increase in the waste’s price.
Furthermore, several different solutions will limit a country’s dependability on specific resources. Once again, the example of the GGBS is quite revealing, as it had been an excellent solution for reducing the carbon footprint of concrete used in the UK. However, with the closure of the last blast-oxygen furnaces in Port Talbot in 2024, the country now relies on imported GGBS to meet the internal demand. This is counterproductive, in sustainability terms, and causes an increase in CO₂ emissions due to the transport of a rather heavy material.
The upcycling of waste like CDW will play an essential role in the transition towards a circular economy and climate neutrality. Like everything else, any upcycling must be implemented in a sustainable way.
A perspective from around the world
Middle East
Recycling of construction materials in the Middle East, particularly in the United Arab Emirates (UAE) and Saudi Arabia (KSA), has gained significant attention. Regulations and initiatives in these countries aim to minimise CDW, which forms a large percentage of landfill contributions.
In the UAE, Vision 2021 targets diverting 75% of municipal solid waste from landfills. Regulations from the Ministry of Climate Change and Environment mandate waste segregation and recycling in construction projects.
Emirate-specific initiatives, like Dubai Municipality’s Integrated Waste Management Strategy 2021-2041, emphasise CDW recycling through specialised facilities. For example, the Dubai Waste Management Centre and Abu Dhabi’s Tadweer operate plants that recycle construction waste into reusable materials like aggregates for road construction.
Moreover, regulations such as Estidama and Al Sa’fat promote sustainable construction practices, including the use of recycled materials.
In Saudi Arabia, the Saudi Vision 2030 emphasises environmental sustainability and waste reduction. The National Center for Waste Management oversees initiatives to increase recycling rates across sectors. The Saudi Investment Recycling Company, established by the Public Investment Fund, focuses on turning CDW into resources for infrastructure projects.
Regulations require contractors to manage and recycle waste generated during construction. Companies are also incentivised to use recycled materials in construction projects, especially within megaprojects like NEOM and Qiddiya.
Other Gulf Cooperation Council countries, like Qatar, Oman, Bahrain and Kuwait, are making significant strides toward recycling CDW, though their progress varies depending on national priorities, resources and infrastructure development.
Hong Kong
Hong Kong’s dense urban environment, limited natural resources and high population density make circular economy practices in construction both an urgent necessity and a complex challenge.
The Hong Kong Government and construction industry has achieved impressive material recovery rates, with over 90% of waste being either directly reused or stored for future use. Despite this success, the outputs of traditional recycling methods are often low-value aggregates used for road bases or fill materials.
Of the waste that ends up in landfill, construction waste constitutes around 25% of the total solid waste sent to landfills, with an average disposal of 4,128t per day in 2022, according to the Environmental Protection Department of the Hong Kong Government. Of this, over 90% is inert material, also known as public fill, which is reused in construction projects or stockpiled for future applications such as land reclamation and site formation. However, the non-inert fraction, which includes timber, packaging materials and organic waste, continues to exert pressure on already strained landfill capacities.
This highlights the need to move beyond conventional waste management practices to more advanced circular economy approaches that prioritise recycling and upcycling.
Academic innovations in upcycling construction waste in Hong Kong include:
- High-performance aggregates – construction waste being converted into high-strength aggregates, lightweight aggregates, sound-absorbing aggregates and thermal insulation aggregates.
- Advanced building materials – partition and paving blocks have been produced using combinations of construction waste, waste glass, incineration residues and biochar.
- Sustainable pavements – durable pavements integrating recycled concrete aggregates, reclaimed asphalt and waste tyres show the potential of upcycling to create eco-friendly infrastructure solutions.
These innovations directly support the Hong Kong Government’s goals outlined in the Waste Blueprint for Hong Kong 2035 and the Climate Action Plan 2050, which aim for carbon neutrality and zero landfill by prioritising sustainable material management.
To complement material upcycling, Hong Kong has embraced modular integrated construction (MiC). Building modules are fabricated offsite in controlled environments to minimise material wastage, improve precision and enable rapid onsite assembly. MiC adoption has grown steadily, especially in public housing and subsidised sale flats, reducing construction timelines by up to 30%.
While still in its early stages, 3D concrete printing also holds promise as another enabler of circularity. Globally, 3D printing has been applied to create bespoke architectural components, reducing material consumption and expanding design flexibility. In Hong Kong, its potential is being explored for non-structural applications that could complement MiC and further support resource-efficient construction practices.
However, despite notable progress, several challenges impede the full implementation of circular construction practices in Hong Kong.
- Space constraints and economic pressures – Hong Kong’s limited land availability, high-labour costs and R&D funding shortages hinder the scalability of upcycling trials and pilot programmes.
- Regulatory and standardisation gaps – while the government has demonstrated an increasing openness to ‘green’ materials, the lack of comprehensive specifications or guidelines in construction codes delays widespread adoption.
- Toxic residues from waste incineration – as incineration becomes a more prominent strategy for managing municipal solid waste, the management of toxic residues – containing heavy metals and dioxins – poses significant challenges. Further research is needed to safely incorporate these residues into construction materials.
Overall, Hong Kong's unique urban challenges demand innovative approaches to construction waste management. Scaling up academic research and fostering collaboration between academia, industry and government can help overcome economic and logistical barriers. Policy support, such as incorporating upcycled materials into government specifications, can drive demand and build confidence among developers and contractors.
By leveraging its technological advancements and committing to policy innovation, Hong Kong has the potential to lead the way in circular construction practices. Transforming waste into resources will not only mitigate environmental impacts but also enhance the resilience and sustainability of the built environment.
Embracing the transformation
From a contractor’s perspective, the transition to circular construction represents both a challenge and an opportunity for transformation. While the building sector is making progress in circularity – largely driven by client demand – the infrastructure sector is also beginning to embrace circular principles, particularly with key materials like aggregates, asphalt and calcined clay use in cement.
'Understanding material flows is crucial for contractors,' says Sam Burdett MIMMM from Skanska. 'We’re seeing increased adoption of Environmental Product Declarations – standardised documents that provide transparent information about a product’s environmental impacts – and material passports, which track construction materials through their lifecycle to enable future reuse. These tools are essential for making informed decisions about material selection and end-of-life planning.'
Recent projects demonstrate the practical potential of circular construction. In Prague, the Mercury development is targeting an ambitious 80% material reuse rate from the demolition of a 1971 office tower.
Similarly, in Gothenburg, demolition materials from an existing building are being incorporated into new construction, with façade bricks being repurposed for both the new building’s façade and interior features. These efforts support a market ecosystem that makes recycled materials as accessible as new ones.
However, contractors face significant challenges in implementing circularity at scale. These include establishing new supply chains, developing verification processes for reused materials and creating robust resource management plans.
'The transition requires new ways of working and testing new solutions,' Burdett notes. 'Success depends on close collaboration with suppliers, designers and waste management partners.'
Looking ahead, contractors are increasingly developing capabilities to manage resources more circularly. This includes implementing minimum standards for material reuse, leveraging technology to enhance resource efficiency, and fostering partnerships to create local circular ecosystems.
While the journey to full circularity is complex, the construction industry’s commitment to sustainability, coupled with growing client demand, suggests a promising future for circular construction practices.
The following page showcases examples of upcycling and reusing specific construction materials.
Recircling glass
The flat glass sector primarily serves the needs of the built environment, automotive, solar and furniture markets, and has been actively trying to source post- and pre-consumer glass for recycling in their manufacturing processes. This would ideally decrease the material’s carbon footprint by increasing melting efficiency and so using less energy.
The NSG Group, UK, has focused on fuel switching and recycling of pre-consumer glass cullet (waste glass from primary production and secondary processing) for some years, and conducted ‘world-first’ trials in St Helens, UK, using hydrogen and other sustainable fuels. One reported milestone was the development of the ‘lowest-carbon footprint glass’.
Meanwhile, the recycling of post-consumer glass is challenging in terms of sourcing and increasing the quality of segregation. Removing chemical contaminants derived from plastic, aluminium from double glazing or laminated glazing waste, and other metals (particularly antimony from end-of-life photovoltaic panels) is challenging.
A stumbling block is the need for cost-effective, high-precision identification and segregation of the chemical contaminants. As a result, the global estimated amount of glass that is unrecycled is around 79%. Funding agencies should encourage new business opportunities for glass recycling. This would make a huge contribution to the sustainability of one the key materials used in the built environment, transport and the energy sector.
Steel reusable
Recycling metals reduces landfill waste, raw material extraction, and water and energy use in manufacturing.
Metal scrap recycling is a well-established process. It is estimated that roughly 95% of all metal scrap is recycled to make more steel. However, less than 20% collected in the UK is used domestically to make more steel. Despite great potential for energy and water reduction in manufacturing, steelmaking is still carbon intensive. The construction sector is looking at alternatives to optimise steel resources.
Structural steel can represent a significant part of a building’s embodied carbon and studies show that reusing it can save up to 97%. The Institute of Structural Engineers’ Circular economy and reuse guide for designers, outlines this potential with case studies.
Fit-out products
Recent figures from a study led by refurbishment company Overbury show embodied carbon emissions of a typical refit is 190kg/m², compared to 600kg CO₂eq/m² for new office buildings.
Buildings are refitted on average five-to-seven years (more frequently in London). After four fit-outs (20 years), more carbon is added into it than in the original structure.
The UK Net Zero Carbon Buildings Standard limits Cat B fit-outs to 260kg CO₂eq/m² in 2025, reducing to 25kg CO₂eq/m² by 2050. To meet those targets, the sector cannot solely rely on products with lower embodied carbon, but need to consider reused products. More companies are setting up take-back schemes, such as RMF for raised modular floors, SAS International for suspended metal ceiling tiles, and Optima for partitions.
Enduring brick appeal
Clay bricks have demonstrated they can withstand the test of time. Their typical lifespan is 150 years – it could be more. However, the built environment is fast-changing and buildings often get demolished before the end of their expected design life.
Products like clay brick therefore become part of the construction demolition waste stream. While roughly 90% do get recycled – according to the Brick Development Association – clay bricks have greater potential to support sustainable solutions in the UK. All bricks have the potential to be recycled into aggregates. Depending on its age, its manufacturing and installation, there is also potential for bricks to be reused.
Timber talks
Wood recycling is well established – for example, as a feedstock for particleboard manufacture and for bioenergy generation (which displaces fossil energy). However, new developments have centred on reclaiming solid wood for recycling into mass timber products, especially from construction and demolition waste.
Work at University College London, UK, has demonstrated glulam and cross-laminated timber products made from secondary timber. However, this requires the solid wood to be removed from buildings with as little damage as possible, aiming to retain the full length of timber elements. This requires deconstruction approaches, rather than demolition.
Metal fixings and other contaminants must then be removed, and the pieces can be prepared to correct sizes for lamination. It has also prompted work on grading reclaimed timber for use in structures and laminated structural elements.
Polymer perspective
Thermoplastics can be softened and reshaped, or reused as is, for the remaining service life of the material if they have not been damaged. For thermosetting materials used in composites (e.g. glass-reinforced plastic) that cannot be softened and reshaped, this is more challenging.
Many thermosetting and composite materials are applied and cured onsite, so are difficult to remove and cannot be reused. Examples include resin floors, adhesives, sealants and coatings.
For composite products, where different materials are combined, disassembly is impossible. For example, some cladding panels include a steel backing or frame, aluminium honeycomb, and polymer-adhesive glass with a polymer or inorganic coating.
Moreover, any new build has a defined service life for the building and for different types of products used within it. The life expectancy in its reuse will be reduced by the length of the previous use. For a product or material with a long-life expectancy, such as a steel beam or marble tile, this might not be significant. However, for a polymer floor tile with a 15-25-year life expectancy, once it’s been used for 10 years, it is unlikely to be acceptable for reuse, regardless of how good it looks.
