How can the world transition to net-zero concrete?

Concrete contributes to 8% of global emissions

The average person may not think of concrete as a significant contributor to the climate crisis. The finger is more frequently pointed at energy generation, road transport, aviation and agriculture. While these sectors are all major sources of emissions, so is concrete. It contributes to 8% of global annual emissions. The heavy industrial processes used to make concrete have historically been powered by fossil fuels, with electrification unable to achieve the necessary temperatures and other alternatives still in their relative infancy.

But simply not using concrete would likely be more challenging still. The UN estimates that two-thirds of the population will live in an urban area by 2050, with many of these areas yet to be built. The IEA is forecasting a 12-23% increase in concrete production by mid-century, from 2018 levels, as trends like urbanisation continue.

Reducing emissions from this sector at the scale and pace needed for it to play its fair share in delivering the Paris Agreement will be no mean feat – but will be necessary, especially as it grows.

To help accelerate and join up the net-zero transition for concrete, the Climate Group launched ConcreteZero last week. Operated in partnership with the World Green Building Council, the initiative will convene businesses across the global concrete value chain to scale, simultaneously, the demand for and supply of low-carbon concrete.

In joining ConcreteZero, businesses involved in construction commit to sourcing only net-zero concrete by 2050, with interim commitments covering 30% of concrete procurement volumes by 2025 and 50% by 2030. Businesses which do not directly procure concrete are also participating at this stage. Their role will be to influence their clients.

The 17 businesses participating are consultancies WSP, Ramboll and Buro Happold; concrete frame contractors Morrisroe and Byrne Bros; London-based property giants Canary Wharf Group and Grosvenor; construction firms Skanska, Willmott Dixon, the Carey Group, Mace, Multiplex Europe and the Clancy Group; Grimshaw Architects; property developer Joseph Homes and engineering multinational Laing O’Rourke.

In time, the initiative will set specific targets for participating concrete manufacturers. It broadly follows the set-up used for SteelZero, launched by the Climate Group in late 2020 in a bid to ensure that as much steel produced, specified, stocked or used by 2050 is net-zero.

To learn more about how ConcreteZero will work and how learnings from SteelZero will be applied, edie spoke with the Climate Group’s head of industry Jen Carson, and to member business Ramboll’s sustainability lead for building structures, Paul Astle. Here, we summarise the key facets of the scheme which they believe can make it a success.

Showcasing possibilities

Carson tells edie that work has been going on behind the scenes for at least a year to prepare for the ConcreteZero launch. This is largely because, as the initiative launched, its first case study was unveiled publicly.

The case study is the Wood Wharf development, spearheaded by Canary Wharf Group (CWG). Next  to the developer’s eponymous London estate, the 23-acre site is currently under construction and will host up to 3,600 homes, two million square feet of office space and a third of a million square feet of retail space. CWG is targeting BREEAM ‘Outstanding’ certification for the development and, working collaboratively, has used recent works on the site as a test-bed for ConcreteZero principles. Collaborators in the project include Ramboll, Arup, O’Halloran & O’Brien, London Concrete and Thornton Tomasetti.

It has often been said that sustainability teams have already, broadly, convinced leadership of their business of the need to accelerate action to cut greenhouse gases. But the devil remains in the detail, with most net-zero targets yet to be deemed credible. Fleshing out that detail may well seem easier if you already have a successful case study to reference.

Carson also notes that her team does not call the concrete sector ‘hard-to-abate’ and wants the new initiative to “change the tone in conversation”. “Because of the speed with which the wider climate agenda has moved, we’re seeing a need to reframe that language and talk about opportunities,” she tells edie. She acknowledges that many of the technologies needed to achieve a global net-zero concrete value chain aren’t yet commercially viable but emphasises how businesses are looking to scale them by investing for the long term, but still using the “many short-term opportunities” that do exist, like using a different mix of constituent materials.

More on this later.

Defining ‘low-carbon’ and ‘net-zero’

It bears noting that, although the Wood Wharf work is well underway, there is currently no global certification or standard that can be used to prove concrete is ‘low-carbon’ or ‘net-zero’. Carson notes that this is one of the differences between SteelZero and ConcreteZero; SteelZero has seen her team working “very closely” with ResponsibleSteel, the world’s first standard and certification programme for the sector.

“Transparency is key in developing a global certification and/or standard,” Carson says. ConcreteZero members will need to report on their progress in using net-zero/low-carbon concrete annually and, in the absence of a standard, will share with each other how they are defining the term.

Carson adds: “Tying into that, the other thing is around universally agreed definitions. This has been front-and-centre and core to both streams of work. We’ve learned from steel that we need to be talking the same language so we have consistency of approach and messaging.”

Understanding local supply chains

Another difference between SteelZero and ConcreteZero is the shape of the global supply chain for these materials.

“One of the really interesting things, when you compare the steel and concrete supply-side pieces is that concrete is regionally and locally produced,” Carson explains. Building in and respecting that supply-side dynamic in the commitment was really important….Steel is far more global and most production is completed by a few dozen companies – it is extremely concentrated. Concrete, in contrast, is super fragmented. 80% of global production is completed by SMEs.”

Ramboll’s Astle adds: “Most concrete is produced within about 10 to 15 kilometres of the site. Consequently, the aggregates, which make up 80-90% of sands and gravels, are also very locally sourced. So we have to understand the local supply chain.”

In other words, the low-carbon concrete available in London may not be the same as that available in Liverpool or Edinburgh. These regional discrepancies already impact how businesses plan projects, covering variations in concrete strength and curing times. Astle notes that, going forward, plans will need to account for the properties of low-carbon concrete.

He says: “If you want to use cement replacements, typically, but not always, they will slow down the curing process. That effect will be magnified if the ambient temperature is lower. In winter months, it can be more difficult to use cement replacements.

“If you want to mitigate these challenges without increasing the cement content, you may need to do more work In the summer months or heat the structure you’re pouring into.” Ramboll is currently investigating the climate impact of heating the structure versus using more cement. It bears noting that the heating is low-temperature.

Taking a tech-agnostic approach

In the short term, one of the most effective ways to reduce embodied emissions in concrete is to reduce the cement content. As Astle hinted at, cement is a major contributor to the embodied emissions of concrete. Carbon Brief stated in 2018 that, if the cement industry were a country, it would be the third-largest emitter in the world. Producing cement involves heating limestone with clays at extremely high temperatures – in furnaces traditionally fuelled by fossil fuels.

“While we are not directly responsible for the procurement, we have a significant role in that stage – and it’s surprising what you can achieve through the specification piece,” Astle says. “What’s so important now is that the specification goes out and we then have that [environmental] conversation. We can check that the contractors have understood what we’re asking for, and they then need to go to their suppliers… because their insight can influence the specification for that project”

Improving energy and material efficiencies can also offer opportunities for emissions reductions in the near-term.

Looking towards the future, Carson acknowledges that a mix of technologies which are currently nascent will play a role, stating: “There is not one technology we can pin all our hopes on.”

Trade body the Global Cement and Concrete Association (GCCA) last year published a roadmap including carbon capture and storage (CCS), electrified processes, alternative fuels and innovations in clinker production. This organisation represents more than 40% of the sector. ConcreteZero is not prescribing a similar roadmap to participants.

At the ConcreteZero launch event, speakers acknowledged that some firms are going all-in with investments in offsetting rather than these emerging technologies, citing lower costs in the short term. But Carson notes that this will do nothing to bring the cost of these innovations down in the years to come as offsets become more expensive, too. ConcreteZero, she says, is “absolutely not” supporting excessive offsetting, as this “delays solving the problem”.

Private-public collaboration

At the moment, ConcreteZero participants all hail from the private sector. But it’s mind-boggling to begin to imagine the amount of concrete which goes through the public procurement process. Around 30 billion tonnes of concrete is used globally each year and, for the majority of this use, the public sector will be involved in some way. So, the make-up of ConcreteZero’s membership may well shift in the coming years.

“Particularly in the concrete space, even compared to steel, there is so much [material] going through public procurement,” Carson says. “We are doing a lot of work here; while our initial focus has been the private sector, we’re already having a substantial number of conversations with the public sector in different geographies. In the UK, we’re speaking with the Department for Business, Energy and Industrial Strategy (BEIS), among others.”

The GCCA, World Economic Forum and Boston Consulting Group recently published a report outlining how national governments would do well to change building codes to ensure the procurement of low-carbon concrete. That report covered governments in the Netherlands, Sweden, Germany, France, the US and the UK. With the search for the UK’s next Conservative Party Leader and Prime Minister underway, time will tell whether they keep to top-line commitments on net-zero, let alone take a specific focus on decarbonising public procurement.