By: Rick Bohan
In an era of increasing extreme weather events brought on by climate change, industry and government are having to strike a delicate balance: how to build new infrastructure in the short term that will last for the long term and all while cutting carbon.
The most widely used material in the world—concrete—has the unique capability to both meet infrastructure demands and sustainability requirements at scale.
This new challenge comes as the annual costs for extreme weather are now reaching hundreds of billions of dollars, but concrete has long proven its worth as a durable and practical material. Resistant against extreme temperatures and weather, concrete is virtually maintenance-free. Cement production is an energy-intensive process, but there are proven solutions across the value chain to reduce the CO2 emissions from cement manufacturing.
The Portland Cement Association (PCA), representing the majority of U.S. cement production capacity and manufacturers, released its Roadmap to Carbon Neutrality in late 2021. The ambitious, far-reaching strategy has a goal of reaching carbon neutrality throughout the cement-concrete-construction value chain by 2050. In this roadmap, PCA charts a course to reduce CO2 emissions and reach net-zero while still meeting the increasing demand for safe, sustainable, resilient infrastructure that withstands the fury of climate-related weather events.
Consumption of concrete is on the rise. In 2020, 378 million cubic yd of concrete were used in the U.S.—a figure projected to grow 3.5% in 2021 to 391 million cubic yd. The spending announced in last November’s Bipartisan Infrastructure Law is expected to add a further 180 million cubic yd over the lifetime of the program, with the first placement of concrete related to the bill anticipated in the second quarter of 2023.
The PCA Roadmap comes at a time when federal, state, and local agencies prepare for a long-term, widespread overhaul of the nation’s roads and bridges—and rehabilitating poor pavements promises to not only improve our roadways, but save fuel and drastically cut CO2 emissions. In the freight sector alone, stiffer road surfaces can result in fuel savings of up to 3%—translating to 2 million tons of CO2.
Decarbonizing the Cement Value Chain: Collaboration is Key
Across every step of the concrete life cycle, from cement manufacturing to final reuse and recycling, the PCA Roadmap provides opportunities, strategies, and solutions to cut CO2 emissions and achieve carbon neutrality. To reach net-zero by 2050, the roadmap outlines strategies across three different phases: production at the cement plant, construction from idea to implementation, and the day-to-day impact from infrastructure use. For each of these phases, the roadmap recognizes the five main areas of opportunity and collaboration: clinker, cement, concrete, construction, and carbonation.
There is no single current technology, process, or product that can get the cement and concrete industry to carbon neutrality. Silver bullets do not exist, but even if they did, they still cannot address the CO2 impacts from the built environment. A system-wide approach that encompasses stakeholders across the value chain is the only viable approach to achieve carbon neutrality.
Crucially, the success of the roadmap’s multi-stakeholder approach could provide a pathway for other industries in their climate response—and formulating such a response will prove vital as the trillion-dollar infrastructure bill provides opportunities for rapid industry growth. The cement and concrete industry has long been ahead of the curve on climate: the cement industry was one of the first to acknowledge climate issues in the mid-1990s, reducing carbon intensity by 11.9% along with general energy consumption while actually increasing production ever since. 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 just 1.25% of industrial U.S. CO2 emissions.
But rather than accept the status quo, the cement industry is driven to take the lead and reduce further, especially given that the construction sector is poised for significant growth. The U.S. is predicted to add another 121 billion sq ft of buildings by 2050—the equivalent of constructing New York City every year for the next 20 years. Of course, this does not account for the trillions of dollars the country is now poised to spend updating critical infrastructure, rehabilitating existing roads and bridges, and expanding construction in growing cities.
The roadmap stakes out near-, medium-, and long-term solutions to move toward carbon neutrality. Each link and phase in the value chain has a specific role to play in cutting emissions, with opportunities. These opportunities within each of the five critical phases, from clinker to carbonation, can jointly reduce CO2 emissions while creating a built environment that is overall more sustainable and resilient—and ultimately, through improvements in reuse and recycling, contribute to a circular economy.
By optimizing clinker composition and manufacturing, enhancing cement ingredients to reduce carbon intensity, exploring the infinite possibilities of concrete mixtures, outlining opportunities in design and construction, and measuring the benefits from the natural process of concrete absorbing CO2 over its lifetime through carbonation, the cement and concrete industry can continue to deliver this vital material while setting out on an attainable path to carbon neutrality.
Optimizing Pavement to Lower Life Cycle Emissions
Collectively achieving carbon neutrality across the entire concrete value chain requires innovation and engagement at every step. Optimizing design and using lower-carbon inputs can help reach this goal.
For example, optimizing designs for the lowest life cycle emissions is especially critical in pavement construction. Stiffer pavements and smoother surfaces in concrete pavements can reduce excess fuel consumption—and save millions of tons of CO2 in the process. Moreover, due to their rigidity and durability, concrete pavements last longer and require far less maintenance over a life cycle that is longer than asphalt.
These benefits can be multiplied over the life cycle of a project by using lower-carbon cement options, and the roadmap highlights Portland-limestone cement (PLC) as an especially compelling option. Used in Europe for more than 40 years, PLC can immediately reduce emissions by 10%. Industry-wide use of PLC, in addition to newer low-carbon cement blends, holds the immediate promise of reducing emissions as demand for new construction grows.
The industry anticipates PLC will account for 36% of all cement by 2040, which will translate into significant emissions savings if this level of utilization is reached—and universal acceptance would reduce emissions even further. However, doing so will require a shift in procurement policies in both the public and private sector which are, in some cases, just too prescriptive or restrictive. By transitioning to performance-based material and design standards, policy-makers can increase the market for commercially available high-performance, lower carbon products like PLC.
Optimizing design also stretches beyond pavements to structures and buildings, with a need to take an intentional and holistic approach rather than defaulting to a status quo that feeds into institutional inertia. If a building or a structure is expected to last decades, for example, the roadmap advocates planning for that—from materials and energy use to design and construction, ultimately optimizing the structure. Realizing these gains in the short term will require collaboration across the entire value chain, but will result in long-lasting energy and emissions benefits.
The Cement Plant: Realizing Upstream Reductions
Before reaching the roadway, cement manufacturers are taking a diverse array of steps to reduce emissions at the cement plant itself. In order to provide a more environmentally responsible product, cement manufacturers have already begun to put roadmap recommendations into practice, leading the shift to carbon neutrality across the wider value chain.
Heating limestone and other raw materials to approximately 2,700˚F to create the finished product, cement production remains the most energy-intensive process along the value chain. While newer cement manufacturing technology is rapidly approaching the limits of theoretical efficiency, the process can be optimized further with gains primarily found in the areas of fuel efficiency. Moreover, there are further opportunities to reduce CO2 through optimizing energy use, cleaner fuels, and utilizing carbon capture, use, and storage (CCUS) technologies.
To begin, heating the limestone used in cement production emits CO2—but to reduce these emissions, manufacturers can replace virgin materials like limestone with already decarbonated raw materials, essentially creating a circular value chain in the process. Rather than virgin raw materials, decarbonated materials have already been processed, so they no longer contain CO2. Decarbonated raw materials currently represent less than 5% of cement manufacturers’ raw material input. However, with the right policies, that amount could be doubled so the industry is targeting this 10% benchmark by 2050.
In addition, as cement manufacturing is a high-temperature pyroprocess requiring combustion to reach the necessary temperatures, alternative fuels in place of traditional fossil fuels like coal and petcoke can reduce those combustion CO2 emissions at this key stage of production. Coal and petcoke make up 60% of the current fuel mix, but the industry wants to cut that amount by a factor of five with a goal of no more than 10% coal and petcoke use in 2050. One option is switching to natural gas which, in the near-term, cuts CO2 combustion emissions by 2%, but increased use of biomass and waste-derived fuels point toward a longer-term, lower-carbon solution. With the right policies and regulations, alternative fuels could make up 50% of the industry’s fuel mix.
Further down the road, CCUS technology has the potential for the greatest emission reductions in the industry. CCUS technology can capture upwards of 90% of process and combustion emissions and counteracts these otherwise irreducible process emissions. This technology is an incredible advancement for the future of sustainable production and can be applied to many industries outside of the cement sector. Bringing this technology to scale will require intense research and development, and while it will not happen in the short-term, it cannot happen in the long-term unless we start that research today.
Society Needs Concrete, Concrete Needs Society
Across the built environment, the benefits of concrete are clear. Concrete is a resilient material that does not rust, rot, or burn; in the long run, this saves time, energy, and resources that would be needed for repairs to damaged infrastructure. Moreover, because of this durability, concrete roads and infrastructure would not require additional carbon emissions to produce additional materials used for repairs.
In the context of our changing climate, this durability is critical. For every dollar spent on resilient construction, $6 can be saved in recovery costs. And as NOAA data shows that such extreme weather events are becoming more common, building with concrete is a more cost-effective way to spend taxpayer money on resilient infrastructure.
Much can change over the lifetime of a road or other structures. Material prices may fluctuate, maintenance budgets may be cut, and the levels of traffic could intensify. As we add climate change to that list of uncertainties, using concrete can address those variables and reduce their impact—and through the roadmap outlined by PCA, these can be managed while reducing the concrete value chain’s CO2 emissions to net-zero.
This snapshot of the PCA’s Roadmap not only shows the steps that cement manufacturers have already begun to take, but also demonstrates that carbon neutrality across the concrete value chain requires every stakeholder to get involved in the process—from engineers and designers optimizing concrete use, to replacing current vehicle fleets with zero-emission alternatives.
Crucially, this also requires bold policy actions at the federal, state, and local levels. Accelerating R&D investment for portions of the pathway toward carbon neutrality—such as CCUS technology—is critical, as are streamlined regulation, siting, and permitting practices. The full product, material, and building life cycle must be considered when developing procurement standards and other policy, and industry credits and recognition for emissions reduction should also be implemented. Beyond those obvious policy measures, market and community acceptance of lower-carbon alternative cements and concrete—alongside other innovations across the value chain—must also occur if the net-zero goal is to be achieved by 2050.
Ultimately the PCA Roadmap is a realistic path forward requiring stakeholders across the value chain to engage and implement. PCA is proud to take the lead in showing them the way forward.
About The Author: Bohan is vice president of sustainability at the Portland Cement Association.
