Cement is the largest single source of industrial emissions on the planet, responsible for 7% of global carbon emissions. If cement were a country, only the US and China would emit more.
These astronomical emissions – 2.8 gigatonnes of CO2 per year – are driven by demand. Cement is the primary ingredient in concrete, of which the world consumes 30 billion tonnes a year. That is enough to fill five million Olympic swimming pools.
So, is the world faced with a choice between using more concrete, and reaching net zero emissions in line with global climate goals?
“I certainly think we will continue to use concrete after we have reached net zero, but not in the way we do today, and not to the same extent,” says Tim Gudmand-Høyer. He is a chief consultant at Ramboll and holds a PhD in civil and structural engineering with a specialty in concrete structures.
“Concrete is a major source of emissions, and we need to find solutions for that. But in many parts of the world, which are in, or expecting, building booms, concrete is a cheap, reliable material, and here it is hard to see the alternative,” he adds.
Experiments in low carbon concrete
Tim Gudmand-Høyer is part of a team at Ramboll that experiments with new ways to reduce the carbon intensity of concrete buildings. Using computational design, they have designed a model community centre in the Kanalbyen project in Fredericia, Denmark, with a carbon footprint of less than 5 kg CO2e/m2 per year.
Hollow, 3D-printed columns reduce the amount of concrete needed for the community centre in Kanalbyen – and the carbon footprint. “The concrete shell designed at Kanalbyen will never be the norm in buildings worldwide. But consider if we could make small tweaks to elements used in all buildings, like foundations or walls,” Tim Gudmand-Høyer explains. “Then one small carbon saving of 5% could have a huge global impact. Pioneering projects like Kanalbyen are inspiring and contributes to finding these new ways and tweaks that are needed in the industry.” Looking ahead to 2050 Because concrete accounts for such a large share of global emissions, it is an industry under intense scrutiny, with predictions, projections and roadmaps to reduce the sector’s climate impact. In their 2050 roadmap towards net zero concrete, from the Global Cement and Concrete Association, the largest drop in emissions (36%) is expected to come from carbon capture and storage (CCS). But Tim Gudmand-Høyer is not convinced CCS can deliver such carbon reductions at scale: “The industry has begun working towards CCS, but in many parts of the world it is unlikely to reach scale or mass adoption because the facilities and investments needed are massive.” Instead, he expects the biggest gains to come from changes to the materials used, and from design practices that are more carbon conscious. “Today, we often use more concrete because it insulates well acoustically, not for its load-bearing properties. If we only use concrete where it is strictly needed for load-bearing, that is one immediate way to reduce emissions." In Tim Gudmand-Høyer’s view, while the building industry is highly optimised with respect to cost and time, the same is not yet true for carbon impact. As such, there is a strong rationale for setting a carbon budget for building projects alongside a financial budget. Moreover, there is a growing awareness of sustainability impacts, and of openness in the construction industry when it comes to sharing best practice on low-carbon innovations. “This leads to more knowledge sharing than is the case with purely cost-reducing initiatives. Because this agenda has so much momentum, including leadership level, it helps accelerate the industry transition,” Tim Gudmand-Høyer ends. Tim Gudmand-Høyer is a contributor to the recent industry guidance paper on how to reduce material use and carbon emissions from concrete structures in the design phase, published by industry organisation Danish Concrete. (In Danish, ed.).