Full Pavement Life Cycle Analysis Will Help the Administration Meet Its Sustainability Goals

On April 22, 2022, the U.S. Department of Transportation’s Federal Highway Administration (FHWA) announced a variety of actions the agency is taking to protect the environment and combat climate change as part of a suite of announcements to celebrate Earth Day 2022. These include new programs and funding under the recently enacted Bipartisan Infrastructure Law (BIL) that will lower transportation sector emissions and accelerate the deployment of clean technologies. In addition, as part of a Department-wide effort to challenge transportation agencies and others to find innovative ways to reduce transportation sector greenhouse gas emissions, FHWA launched its own highway-specific “climate challenge” on Quantifying Emissions of Sustainable Pavements. This challenge presents a unique opportunity to improve the sustainability of pavement structures and work toward goals for net-zero emissions.

The American Concrete Pavement Association (ACPA) applauds FHWA’s Climate Challenge initiative as an important step toward truly sustainable pavements. The concrete pavement industry is fully committed to establishing and reducing our embodied carbon footprint and is actively working to implement and adopt techniques and tools like Environmental Product Declarations (EPD) and Life Cycle Assessments (LCA) to move our sector toward a more sustainable built environment. We embrace the use of these tools to help measure and document progress toward net-zero emission pavement solutions.

What’s more, our industry already has made huge strides toward increasing the sustainability of concrete pavements. Recent steps include mixture optimization, maximizing the use of Supplementary Cementitious Materials (SCMs), embracing portland-limestone cement (PLC), and more. The embodied CO2 footprint of a typical paving mixture today is as much as 40 percent lower than just a few decades ago.

While our industry is fully committed to reducing the embodied carbon footprint of our pavement mixtures, we are also acutely aware of the broader carbon footprint associated with pavements. It is the concrete pavement industry’s perspective that we should and can embrace all available opportunities to reduce the overall life-cycle carbon emissions associated with pavements. While the importance of reducing our embodied carbon footprint cannot be understated, the embodied carbon footprint is only part of a concrete pavement’s overall life cycle footprint. In some cases, the portion of embodied carbon in a pavement’s overall life cycle is very small. When specifying a new pavement or overlay project, we aren’t just selecting a material – we’re selecting a solution that will be in service for decades. Therefore, when procuring a material with the goal of lowering carbon, we certainly should consider embodied impacts, but not at the exclusion of all the other impacts, including use-phase impacts.

The reason for this is that we could select a low-embodied carbon solution (low EPD) that has to be reconstructed every few years. Although this could meet some low-carbon EPD requirements, it would be counter to the larger objective of reducing overall carbon emissions. We could inadvertently make things worse for our planet by focusing solely on the embodied impacts. Use-phase impacts are important and should therefore also be considered when making procurement decisions — especially since these pavement assets have impacts that last for decades.

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As shown by this graphic, we can see the pavement’s various life cycle stages on the bottom, from raw materials extraction, manufacturing, and construction, through the use stage and end-of-life stage. From this graphic, we can see that EPDs only cover the Product stage (A1-A3). In other words, EPDs currently quantify the embodied impacts only and do not capture the rest of the life cycle stages (A4 through B, C and D).

Only a full pavement life cycle assessment (LCA) can capture that. As the graph illustrates, the life cycle impacts beyond the materials stage can be quite significant. In some cases, use-phase impacts can dwarf the embodied impact (note the blue and orange lines in the diagram).

In order to make meaningful and lasting reductions in the overall life-cycle environmental impacts of our pavement investments, we need to reduce our embodied impact — something EPDs can help us do — AND we need to minimize our use-phase impacts as much as possible (since those impacts often dwarf the embodied impacts). As we already have the tools to help us accomplish this, the opportunity for the pavement sector to make impactful and lasting reductions in the overall carbon impacts of our roadway infrastructure is within reach.

To learn more about the sustainability of concrete pavements, visit https://www.acpa.org/why-concrete/sustainability-environmental/ or contact the ACPA at acpa@acpa.org.