Building Toward Carbon Neutrality

The cement industry faces a future of reformation as it works toward reducing emissions.

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Extreme weather events driven by climate change are emerging as a new normal for communities across the United States. From deep freezes in Texas to Kentucky’s recent outbreak of tornadoes, the effects of climate change are ramping up.

In response, authorities at the local, state, and federal levels are seeking to rehabilitate American infrastructure to make it more resilient and aligned with a sustainable future. Additionally, the country has become more aware of our impact on the planet and is collectively looking to reduce carbon emissions as a part of that sustainable future.

Coupled with rising incidents of extreme weather, the United States has entered a construction boom expected to produce the equivalent of 20 New York Cities between 2017 and 2050. In the age of ecological awareness and climate change, these future buildings and their materials are of utmost importance as the construction sector currently accounts for almost 40% of global emissions. While the majority of emissions are created from the operations of buildings, 11% is attributed to building materials and construction processes. 

As a result of this ongoing growth, demand for concrete–a durable and resilient material, which does not burn, rot, rust, or warp–continues to grow. The cement and concrete industry is facing a definitive challenge: striking a balance between reducing carbon emissions and meeting increased demand.

Concrete’s Impact on Modern Life

Concrete is one of the most consumed substances globally, second only to water. On a global scale, concrete’s ton for ton usage is twice that of steel, wood, plastics, and aluminum combined. More than 10 billion tons of concrete are produced globally every year, of which 500 million tons are produced in the United States.

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The five links in the value chain include the production of clinker, the manufacture and shipment of cement, the manufacture of concrete, the construction of the built environment, and the capture of carbon dioxide using concrete as a carbon sink. Each link identifies specific targets, timelines, technologies, and policies to reach the goal of carbon neutrality.

Cement is the main ingredient of concrete. Given the scale of its usage, the cement industry has worked hard to reduce its carbon emissions. This commitment began in the 1990s, and, since that time, the industry has reduced energy consumption and lowered carbon intensity by 11.9%, while simultaneously increasing production. 

According to Environmental Protection Agency data, cement plants have reduced energy-related carbon emissions by 1.5 million metric tons annually, and the industry is responsible for 1.25% of U.S. CO2 emissions.

However, an industry fact of life is that cement production remains the most energy-intensive step in the concrete value chain. Materials used to produce cement are heated to approximately 2,700 degrees Fahrenheit to convert limestone and other materials first into clinker and finally into Portland cement.

Fortunately, the industry recognizes its carbon footprint and has made bold commitments to reach carbon neutrality across the entire concrete value chain, from cement to construction.

Roadmap to Carbon Neutrality

Last year, the Portland Cement Association (PCA) took the first step toward achieving this net-zero goal with the release of its Roadmap to Carbon Neutrality. This report provides a pathway for the entire concrete value chain to realize carbon neutrality by 2050. Through the Roadmap, PCA identifies opportunities to reduce carbon emissions in what it terms the five Cs of the value chain: clinker, cement, concrete, construction, and carbonation (concrete as a carbon sink).

There is no single breakthrough in technology or process that can get the cement and concrete industry to carbon neutrality. Yet, as the links of the value chain show, even if such a breakthrough were to be made, it would not achieve carbon neutrality for the built environment: each link is only as strong as the others in the chain. Therefore, as outlined in the Roadmap, a system-wide approach that encompasses stakeholders across the value chain is required.

At every stage of the value chain, the Roadmap outlines a diverse array of short-, medium- and long-term recommendations to reduce system-wide CO2 emissions and help achieve carbon neutrality by 2050, ultimately creating a more sustainable built environment.

U.S. cement manufacturers can take several early measures to reduce their CO2 emissions in the clinker and cement stages. These range from using alternative fuels and decarbonated materials in the clinker production stage to more expansive production and adoption of lower-carbon cement blends such as Portland-limestone cement (PLC), which can immediately reduce emissions by 10%. Industry-wide use of PLC holds considerable potential to reduce emissions as demand for new construction grows.

Companies at the cement production stage of the value chain are already taking steps to achieve carbon neutrality by 2050. For example, Martin Marietta’s plant in Redding, Calif., has started to burn pistachio shells for additional fuel.

Further down the value chain, the concrete industry, designers, and the construction sector are encouraged to optimize designs for the lowest life-cycle emissions, which is especially critical in pavement construction. For example, stiffer pavements and smoother surfaces in concrete pavements can reduce excess fuel consumption—and save millions of tons of CO 2 in the process. 

Life-cycle concerns are especially critical in the carbonation step of the supply chain. Concrete surfaces absorb CO2, and over the course of its life, a building or pavement can reabsorb 10% of cement and concrete production emissions.

Collaboration and Commitment

There is no silver bullet that can achieve carbon neutrality at a stroke. To make meaningful, sustainable steps across the entire concrete value chain to achieve carbon neutrality requires each step to work together.

As an example, the cement and concrete sectors can work together to prioritize the use of PLC and other low-carbon cement mixes, support research on mix design, and accelerate a transition to alternative fuels and low-emission vehicles. 

Additionally, the concrete sector and its downstream partners–including the construction sector, designers, and architects–can cooperate on measures like optimizing concrete mixes to specific products, performance-based standards, and taking a whole life-cycle approach to sustainable construction.

However, the key driver for this system-wide change must come at the policy level. According to Rick Bohan, VP of Sustainability at PCA, “Policymakers will play a critical role in driving market innovations, regulatory refinements, accelerated research, and funding to stimulate, support, and sustain the cement and concrete industry in its quest for carbon neutrality.” 

Bohan adds that meaningful progress can also be made by overcoming today’s institutional inertia. “We have the materials, like fly ash and slag, available today to transform the cement and concrete sectors, but convincing architects, engineers, code officials, and municipalities to use them has proven to be challenging.”

The Road to Net-Zero

Over the life-cycle of a building, several variables must be factored in. Material prices may fluctuate, maintenance budgets may be cut, and traffic levels could intensify. As we add climate change to that list of uncertainties, using concrete helps manage these variables while reducing the concrete value chain’s CO2 emissions to net-zero.

Reaching net-zero requires broader commitments from everyone that uses the built environment. Policymakers must incentivize market innovations and regulatory shifts required to make carbon neutrality achievable. The concrete and construction sectors must cooperate on optimized concrete mixes with low-carbon cement. Last, the cement sector must reduce emissions at its energy-intensive manufacturing stage. The stakes for greater sustainability could not be higher.

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