The Emissions Impact of Concrete
Concrete is the most consumed material in the world, second only to water, and is responsible for over 7% of annual global anthropogenic CO2 emissions. Virtually all of this concrete goes into the built environment (i.e. buildings, landscapes, and infrastructure), and is responsible for more than twice the emissions of the aviation industry9. There are steps individuals can take from the supply side and the demand side to reduce concrete emissions. For example, designing our structures to use each cubic unit of concrete more efficiently can lower demand and reduce emissions by 22%. Ultimately, to reach net-zero, close collaboration between all stakeholders involved in the production and use of concrete is required1.
A variety of ingredients can be combined to produce a wide variety of concrete mixes. Understanding the production of each ingredient and its impact on the characteristics of the final product can help designers specify greater amounts of lower emission concrete.
Using less cement is the most impactful way to reduce the emissions footprint of concrete.
The Emissions Come from Clinker
Concrete is composed of aggregate and binder. Portland cement, the binder that is used the vast majority of the time, is responsible for over 90% of concrete’s emissions1. Nearly 95% of cement’s emissions come from clinker1, which accounts for 91.4% of the material substance of cement3.
Clinker is produced by heating limestone and clay to 1,450°C, which precipitates a chemical reaction called calcination. Energy emissions from heating the kilns accounts for 35% of concrete’s emissions. The calcination process releases CO2 in great amounts, resulting in 53% of concrete’s emissions1.
Reducing the impact of clinker is key to decarbonizing the sector. This can be done by reducing and replacing the amount of clinker used in cement and concrete. These solutions are ready today and reduce both the costs of production and environmental impact of concrete1.
Concrete in Context
Globally, the cement and concrete industry is highly localized1. The average travel distance for in-situ concrete is 16km/10miles2. The average distance for concrete’s raw materials is 48km/30miles2. On one hand, that makes it difficult to make widespread change across the global system. On the other hand, it makes it easier for individual stakeholders to make change within their local context.
Collaboration is the Cure
The most important key to success is collaboration. This globally localized industry can only cure the emissions problem with a mix of supply-side and demand-side solutions that are explored collaboratively among all stakeholders to develop compliant and appropriate low-carbon solutions. Decisions made at every level affect all other stakeholders.
RESOURCES
1 | Cement and Concrete Sector Transition Strategy: Mission Possible Partnership
2 | Low Carbon Concrete Routemap: Institution of Civil Engineers
3 | Carbon Leadership Forum Material Baselines for North America
4 | How Basic Shapes Influence Commercial Architecture
5 | Sensible House: Building Shape/Orientation
6 | 10 Design Commandments for Cutting Your Building’s Embodied Carbon: OneClickLCA
7 | Low Carbon Concrete Prepared with Scattering-Filling Coarse Aggregate Process
8 | ASCE/SEI Sustainability Guidelines for the Structural Engineer (See Concrete chapter)
9 | The material that built the modern world is also destroying it. Here’s a fix.
Scaling Limestone Calcined Clay Cement (LC3): Learnings from the First Movers
Scientific Principles of Concrete
Specifying Sustainable Concrete
Case Study – Measuring and Reducing Embodied Carbon in Concrete
ASCE/SEI Structural Materials and Global Climate (See Concrete chapter)
The New Carbon Architecture, Bruce King (see Concrete Chapter)
Concrete CO2 Fact Sheet (NRMCA, 2012)
ASCE. (2010). Sustainability guidelines for the structural engineer, D. Kestner, J. Goupil, and E. Lorenz, eds., Reston, VA.
SEE ALSO
