Looking at the full lifecycle of infrastructure, concrete and cement enhance sustainability
- Concrete structures have similar amounts of embodied carbon dioxide and energy when compared to other building materials. Embodied carbon dioxide is the carbon dioxide associated with building construction, including extracting, transporting and manufacturing materials.
- Concrete is the most durable, resilient building material due to its long service-life and ability to withstand the elements, and it requires less maintenance and repairs, meaning less energy and emissions for upkeep compared to other building materials.
- Concrete actually absorbs carbon dioxide over its entire life and captures it permanently, but unlike other sources which may also absorb carbon dioxide, such as wood, it will not rot and release that carbon dioxide back into the environment.
Concrete made with cement is the most used man-made product in the world. As climate concerns grow, these foundational materials are uniquely positioned to help us meet the challenges of a more sustainable world.
Carbon dioxide emissions from all sources, including the building sector, are receiving increased attention. While the cement industry was one of the first to acknowledge climate change issues and implement tangible steps to reduce emissions through programs focused on process and energy efficiency, the major sustainability benefits of concrete made with cement are not widely known.
Concrete and cement play an important role in our economy and are an essential part of a sustainable future.
We need to take a lifecycle approach
In order to truly determine which building materials are the most sustainable, we must consider them in terms of their entire lifecycle, that is, from sourcing and production through end use and disposal. Specifically, for building materials such as concrete, wood, steel and glass, the best way to measure environmental impact is by looking at their embodied carbon and energy.
Embodied carbon is all the carbon dioxide emitted and energy expended during the sourcing, manufacture, transport, construction use, reuse, recycling and disposal of building materials.
Why a lifecycle approach?
Looking at just one stage of a material’s service life is not an accurate measure of how much carbon dioxide or energy is expended in relation to that material and it is misleading when we think about solving a complex challenge such as climate change.
Although cement’s carbon footprint for production is higher than some other materials, concrete itself has a low carbon footprint. In fact, concrete has similar embodied carbon (e.g., carbon per kilogram of concrete) to most common building materials, but its impact appears much greater because we use so much of it – it’s the second most consumed material on Earth after water. Concrete’s global prevalence is for good reason – it is available, durable, versatile and cost-effective. It is also sustainable, playing a part in limiting or reducing building emissions and being 100% recyclable.
A lifecycle assessment of several building types conducted by MIT has shown that embodied environmental impacts of buildings are around 10% of the total lifecycle greenhouse gas emissions; energy use (such as heating, cooling and maintenance of the building) represents the vast majority of environmental impacts. Simply put, the impact of creating a building is just a small part of the picture, compared to the energy and emissions required to operate the building over its life.
Production (the 10%)
Cement and concrete production is heavily regulated and monitored, with standards in place for each step in the manufacturing process to measure and understand environmental impact. But production within other building material industries is not always monitored in the same way. Often the energy and emissions associated with sourcing materials and transportation, such as in the timber industry, is not considered when measuring embodied carbon.1
In addition, cement and concrete production offers opportunities for innovation and increased efficiency. As part of their ongoing work to lower emissions, many cement manufacturers have recently introduced a type of cement called portland-limestone cement in the U.S., which lowers carbon dioxide emissions about 10% during production. Many have also incorporated alternative fuels like biomass and waste materials into production, which are less carbon intensive and result in lower emissions. Additionally, promising innovations such as carbon capture and storage technology are being evaluated which can help cement plants reduce their overall carbon footprint.
Construction and use (the other 90%)
The most sustainable building is one that you only have to build once and can maintain efficiently. Durability and resilience are vital parts of sustainable construction, as insufficient durability or resilience may result in a reduced building life, unexpected repairs or even total reconstruction, with all their associated costs and social impacts. Concrete structures typically have a longer service life than ones made with steel and timber, as they do not rust or rot and are pest resistant. Moreover, concrete structures can be repurposed avoiding having to destroy and reconstruct buildings using new materials which would create pollution and use more energy.
Over the course of a concrete building’s lifecycle, concrete is continually absorbing and trapping carbon dioxide from the air and offsets more than 11% of the carbon dioxide emitted to produce it. Importantly, concrete will not burn, rust, rot, or re-release that carbon dioxide back into the environment.
Wood, the only other construction material that can sequester carbon dioxide, captures carbon dioxide while the tree is alive and will emit that carbon dioxide if it rots or burns.
Cement and concrete building materials also exhibit excellent thermal insulating mass, improving the energy efficiency of buildings. Studies by MIT have shown that homes with concrete walls can use 8 to 15% less energy than other homes.2
End of Life
Concrete’s unparalleled durability enables buildings to be reused and repurposed, extending the lifespan of construction and reducing waste over time. Additionally, concrete is 100% recyclable – structures built from concrete can be crushed and recycled for other functions without material loss or pollution. Every exposed concrete surface absorbs carbon dioxide and deconstructing a concrete building and crushing the concrete into pieces offers the potential for greater carbon dioxide uptake.
When determining which building materials to use for our infrastructure, we must look at the entire life cycle of the structure (building, road, bridge) to understand how the materials it’s made from impact its use phase. Only then can we make informed decisions to move us closer to our sustainable development and emissions reductions goals.
For more information about the sustainability properties of concrete, visit Sustainability Practices in the Cement and Concrete Industry.