Envision welcomes Chris Heyworth to the Board as non-executive director
As a leading provider of sustainability and net zero advisory services, Envision has experienced significant growth. In…
Introduction
The construction industry is having to address its significant contribution to climate change by reducing its associated embodied carbon. While reducing these emissions is a vital step toward a more sustainable future, achieving this goal is often easier said than done. Transitioning directly from traditional construction methods and materials to radically alternative methods and materials, such as steel frames to timber frames, for instance, presents both technical and logistical challenges for many design teams.
In this article, we explore three key construction materials that we are dubbing the “usual suspects”, as these are the materials that, from our experience with BREEAM, Net Zero and Whole Life Carbon Assessments, are often targeted for embodied carbon reduction due to their significant embodied carbon footprints: clay brick, concrete and steel. We will address why each of these materials have high upfront embodied carbon costs, we will then highlight the cutting edge innovative solutions that are beginning to be utilised within the industry in an attempt to dramatically reduce their carbon footprints without compromising on performance or feasibility and with as minimal impact on supply chains as possible. These design innovations demonstrate how the challenges of moving away from traditional methods can be overcome without considerable disruption to allow for easier uptake across the industry.
This article was inspired from a team visit to the Energy Revolution exhibition at the London Science Museum during an Envision team enrichment day. The experience highlighted the important role of innovation in addressing sustainability challenges and prompted a reflection on how similar advancements could help reshape the construction industry into a more forward thinking and progressive industry.
Suspect #1
Brick
Brick is a material often found in building facades, from smaller developments such as residential homes, to much larger developments such as offices and hospitals. This is mainly due to it being a material that is valued for its durability and versatility.
Whilst the overall use of brick has decreased since the 1970s, brick continues to be an important material, with approximately 80% of new build homes being brick built according to the Low Energy Transformation Initiative (LETI). However, its production comes with significant upfront environmental costs. The process of firing clay bricks at high temperatures consumes substantial amounts of energy, often relying on fossil fuels such as coal or natural gas to achieve them. For a material as integral to building traditions, these challenges make reducing its carbon footprint a priority.
Fortunately, there is already a strong market for the use of reclaimed bricks within the industry once they have been salvaged from a refurbishment or demolition project. However the initial reclaiming of brick can sometimes be problematic, unlike traditional lime based mortar, modern cement-based mortars makes cleaning brick for reuse difficult. This issue can be circumvented in part by increasing the popularity of specifying lime mortar for a more circular approach. This is due to lime mortar being softer than traditional clay brick, so unlike with modern hard concrete mortars (e.g. Portland Cement Mortar) demolition contractors are less likely to damage the bricks as they are disassembling them.
Whilst the reuse of reclaimed bricks is proving to be helpful in reducing the industries reliance on the constant manufacturing process of new clay bricks they don’t ultimately solve the core issue, which is the carbon intense process of firing bricks due to the typical use of coal to achieve the high temperatures required for the process.
This is where alternative brick types such as K-Briq and Hybrick excel as they not only utilise recycled construction and demolition materials, which minimises resource extraction and transportation impacts but also significantly reduces the amount of firing that is required. In Hybrick’s case the associated upfront embodied carbon is further reduced through the use of green electrolytic hydrogen generated via renewable electricity. A study funded by the Department of Business, Energy and Industrial Strategy (BEIS) found that on average bricks fired by green electrolytic hydrogen produce around 88% less CO2e compared to traditional methods (BOF) per MJ of energy used as can be seen in Figure 1.1.
Key Links:
https://www.leti.uk/specification
https://www.mbhplc.co.uk/sustainability/hybrick/
Suspect #2
Concrete
Concrete foundations, block frames and walling are also often found in many modern construction projects, often specified for their ability to sustain large amounts of weight across large expanses. Concrete, however, is a major contributor to global carbon emissions, accounting for approximately 8% of worldwide CO₂ emissions. This is largely due to the energy-intensive process of manufacturing cement, a key ingredient in concrete, which typically involves heating limestone to high temperatures.
When it comes to reducing the embodied carbon associated with concrete, there are two key strategies:
- Leaner design solutions that reduce the total volume of concrete required
- Enabling the production of concrete with a lower embodied carbon per m3
As a general guideline, it’s important not to have prescriptive specification but instead allow for performance based specifications for concrete, particularly regarding strength and curing time, and to permit the use of secondary cementitious materials (SCMs), also known as cement replacements, such as ground granulated blast furnace slag (GGBS), fly ash, and silica fume. A literature review performed by the Institution of Structural Engineers (IStructE) found that whilst global supplies of GGBS must continue to be fully utilised to reduce overall Portland Cement (PC) demand, due to a global GGBS shortage any local increase in the amount of PC substituted with imported GGBS is unlikely to decrease global emissions, which questions the benefit of the increased use of these on a project level as it may not be decreasing the overall global emissions. The primary strategy should always be to reduce quantity, however material innovations are continuing to develop, along with the supply chain, which will hopefully help with these global demand issues in the future.
All concrete mixes compliant with BS 8500 are primarily based on Portland cement (CEM I), but most incorporate SCMs, which have significantly lower CO2 emissions compared to CEM I. In the UK, the most commonly used replacement cements are GGBS and fly ash, allowing for up to 85% cement replacement under the current BS 8500 guidelines.
Additionally, there are innovative low-carbon cements, such as belite cement, pozzolan cement, and metakaolin, which are available and in development, but they are not yet included in BS 8500, limiting their current applications and availability.
A greener alternative for concrete blocks that is currently available on the UK market though is GreenBloc, which is a pioneering solution that replaces traditional Ordinary Portland Cement (OPC) blocks with low-carbon alternatives and incorporates recycled aggregates. As a result, carbon reductions of up to 80% compared to conventional OPC-based concrete blocks have been found. GreenBloc maintains the structural integrity and performance of traditional concrete blocks as it has a bulk dry material density of 1850-2000kg/m3, making it suitable for a wide range of applications, including foundations, load-bearing walls, and partitions.
Envision has performed a comparison assessment between a building specification utilising traditional British Concrete Blocks and the same building specification using the Greenbloc alternative, and found that a building design with the only significant difference being the concrete block type utilised, could achieve an overall reduction of circa 10 kgCO2e/m2 at the whole building level, see Figure 2.1.
Key Links:
https://www.leti.uk/specification
https://ccp.ltd/blocks/greenbloc/
https://www.istructe.org/resources/guidance/efficient-use-of-ggbs-in-reducing-global-emissions
Suspect #3
Steel
Steel is one of the most utilised materials in modern construction, as similarly to concrete it can also sustain large amounts of weight across large expanses. A key advantage of steel use over concrete, particularly in the construction of industrial buildings however, is it’s high strength to weight ratio which allows for significantly less material to be used for the same application.
Traditional Steel production methods are, however, one of the most carbon-intensive industries, contributing around 7-9% of global CO2 emissions. Traditional steelmaking processes, such as the basic oxygen furnace (BOF) method, rely heavily on coal, both as a reducing agent and as a fuel source. This process is efficient but comes at a cost of releasing significant CO2 emissions—approximately 2.5 tCO2e/tonne of steel produced. Moreover, the reliance on fossil fuels for energy-intensive smelting exacerbates the sector’s carbon footprint, making it a significant challenge in the transition to a low-carbon economy.
Green steel can now be widely found within the industry. This refers to steel that is produced with significantly reduced carbon emissions compared to steel produced from traditional steelmaking processes. One of the key technologies enabling green steel production is Electric Arc Furnace (EAF) technology, which uses electricity to melt scrap steel or direct reduced iron, rather than relying on coal in blast furnaces. EAFs can be powered by renewable energy sources, making them a more sustainable option and are becoming more available in the UK and across Europe as a whole.
Additionally, the integration of hydrogen into the steelmaking process offers a supplementary route for further reducing carbon emissions. By using hydrogen as a reducing agent instead of coal, the production of steel can shift towards a process that emits water vapor instead of carbon dioxide, significantly lowering the overall carbon footprint of steel manufacturing. In addition to hydrogen-based reduction, innovations in recycling scrap steel and the use of alternative energy sources further support the carbon-reducing potential of Green Steel. By increasing recycling rates, Green Steel reduces the need for primary iron production, thus lowering both environmental impact and resource extraction.
An example of Green Steel is ArcelorMittal’s xCarb. This product is produced in an EAF and includes innovative bio-coal which is derived from forestry and agricultural waste. It also utilises carbon capture and reuse from their current BOF plants and, most innovatively, uses Hydrogen to reduce the iron ore which significantly reduces the amount of carbon emissions associated with steel production. An EPD comparison assessment between UK Tata Steel, ArcelorMittal Standard Steel and ArcelorMittal xCarb steel, found that ArcelorMittal’s xCarb steel produces 64% less associated carbon emissions than standard ArcelorMittal hot rolled steel and 83% less than UK Tata steel standard structural steel, see Figure 3.1.
Key Links:
https://www.leti.uk/specification
https://corporate.arcelormittal.com/climate-action/xcarb
Conclusion
In closing, we have examined three construction materials (brick, concrete, and steel) that are key to the construction industry, that we have termed as the “usual suspects” in the context of embodied carbon reduction. This brief analysis, has highlighted the significant embodied carbon footprints associated with each of these materials and the reasons behind their high upfront embodied carbon costs.
Innovative solutions that focus on circularity, reduction of manufacturing related emissions and reduction of carbon emissions associated with extraction and transportation have begun to emerge within the industry. These advancements can dramatically reduce the carbon footprints of these materials while maintaining performance and feasibility, all with the aim of having minimal disruption to supply chains to facilitate easy implementation. These material innovations illustrate that the transition away from traditional methods is not only possible, but can be achieved with currently available technology and ideally will be more broadly adopted across the construction sector as we progress towards 2030.
At Envision, we specialise in assessing and supporting the transition to more sustainable construction materials and practices through services that we offer such as LCA for BREEAM, Whole Life Cycle Assessment (WLCA) and Net Zero Carbon Life Cycle Assessment (NZC LCA). These services can enable us to evaluate the full environmental impact of a construction project from start to finish, helping clients make informed decisions about materials, design, and construction methods throughout the design and build process. By integrating sustainable material alternatives we assist our clients in achieving substantial reductions in embodied carbon, ultimately with the goal of driving the industry closer to a more sustainable and carbon-neutral future.
Written by: Jacob Broad
Reviewed by: Elise Hewat
