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 full lifecycle impact of cement and concrete, visit Cement and Concrete Lifecycle.
The role of concrete in improving the efficiency of our roads
Fuel consumption and related emissions from vehicles depend on a number of factors like the size of the vehicle and the type of engine, but most drivers might be surprised to learn that the quality of the roads we drive on also impacts the amount of fuel our vehicles use. On roads where surface conditions are poor, vehicles consume more fuel beyond what is actually needed to move, which leads to excess fuel consumption and emissions.
Damaged city roads can increase the amount of fuel used – and the associated greenhouse gas emissions – by as much as 15%.
Concrete offers the most fuel-efficient pavement option. Because of its rigidity, concrete pavement can enhance the fuel efficiency of vehicles that travel on concrete pavement roads when compared to other pavements, and due to its durability, it requires less frequent maintenance and doesn’t wear down as quickly as other pavements.
If concrete pavements were used by the entire U.S. road system, fuel consumption is estimated to decrease by 3% nationwide, which corresponds to a reduction of approximately 46.5 million metric tons of greenhouse gas emissions.
Three key pavement factors affect a vehicle’s fuel efficiency
- The roughness of the road, commonly seen and felt as cracks and potholes
- The texture of the road’s surface, which impacts traction when wet
- The likelihood that the pavement will bend under the weight of the vehicles
As these three factors create additional, unnecessary friction for vehicles and reduce their fuel efficiency, optimizing pavement conditions can reduce carbon dioxide emissions. There are two strategies for creating more optimal pavement conditions: build stiffer pavements and maintain smoother pavements – and concrete pavement offers both.
Facts and stats
Studies across the U.S. have shown the impact of poor pavements:
- An analysis of approximately 50,000 miles of highway in California found that over a five-year period 1 billion gallons of excess fuel was used.
- A study of 5,000 miles of Virginia’s interstate highways found that excessive fuel consumption resulted in 1 million tons of carbon dioxide over a seven-year period.
- When looking at 40-ton trucks (used for freight and trucking), decreasing the impacts of deflection through stiffer roads can lead to a fuel savings of up to 4%, which translates to 2 million tons of carbon dioxide.
For additional information, please visit the MIT Concrete Sustainability Hub.
For more information about the sustainability properties of concrete, visit Sustainability Practices in the Cement and Concrete Industry.
The role of concrete in building a low-carbon, circular economy
Every year, the U.S. uses approximately 260 million cubic yards of concrete to build highways, bridges, runways, water and sewage pipes, buildings and homes, dams, sidewalks and driveways. As the second most used material on the planet after water, the U.S. cement industry is committed to minimizing emissions, waste, energy consumption and the use of virgin raw materials.
Cement is becoming more energy efficient – and the industry continues to progress on efficiency
The cement industry began to address climate change in the mid-1990s—one of the first industries to do so.
- The industry has reduced its use of traditional fossil fuels by over 15%.
- In 2020, The Environmental Protection Agency ENERGY STAR® Program recognized 95 manufacturing facilities in the U.S. as ENERGY STAR® certified for operating in the top 25 percent of efficiency performance in their respective industry sectors. The cement industry represented 13 of those facilities.
- According to 2019 ENERGY STAR® data, cement plants have reduced energy-related carbon emissions by 1.5 million metric tons, annually.
- Since 1990 manufacturers have reduced carbon intensity by 11.9% along with general energy consumption while actually increasing production.
Leading the use and development of alternative fuels
The cement industry is a leader in sustainable material and fuel use. In fact, the cement industry expands the circular economy by diverting waste materials from landfills and uses them for fuel or incorporates them as valuable additives.
- Burning alternative fuels in cement kilns like scrap tires, packaging, plastics and solvents conserves valuable fossil fuels while safely destroying wastes that would otherwise be deposited in landfills.
- Elements like aluminum, iron and silica that are used to produce clinker can come from industrial byproducts of the coal and steel industry, creating better and more sustainable uses for these byproducts.
- The Construction Materials Recycling Association estimates that about 140 million tons of concrete are recycled each year in the U.S., reducing the environmental impact of construction projects.
Lowering emissions in buildings and our urban environments
The durability, resiliency and insulating qualities of cement-related products lower our environmental footprint as a society. Considered across their full lifecycle, cement and concrete building materials are also valuable contributors to a low-carbon circular economy.
- According to the MIT Concrete Sustainability Hub, by adopting the latest building codes and concrete mixes, emissions from U.S. office buildings could decrease by 12%.
- Concrete does not rust, rot or burn, saving energy and resources needed to replace or repair damaged buildings and infrastructure.
- Concrete makes urban areas cooler as its lighter color reflects more sunlight than other, darker materials.
- Because of its durability, concrete structures will not require additional carbon release to produce additional materials used for repairs.
- Over time, concrete actually absorbs carbon dioxide from the ambient air, returning a portion of emissions from the cement manufacturing process to the building itself.
- In fact, for all of the concrete produced in the U.S. between 1990 and 2018, more than 300 million metric tons of carbon dioxide will be adsorbed and sequestered by concrete over its service life.
Sustaining our transportation network
A well-functioning transportation network is the backbone of the U.S. economy and essential for U.S. businesses to compete globally and provide the best value to American consumers.
- Because of its rigidity, concrete pavement can enhance the fuel efficiency of vehicles that travel on concrete pavement roads when compared to other pavements.
- Concrete structures, including pavement, are long-lived – concrete pavement has an average service life of 30-50 years.
- Concrete pavement is less susceptible to damage from heavy vehicles and requires little to no maintenance throughout its service life.
- Concrete pavements do not require lengthy lane closures, with roads able to reopen within as little as six hours. This reduces time-in-traffic auto emissions.
For more information about how concrete is the best choice for sustainable pavements, visit Reducing Vehicle Emissions and Improving Fuel Efficiency.