Federal agencies have spent more than two years reviewing carbon dioxide emissions associated with load-bearing construction material processing or production. Officials recognize regional or local factors affecting the CO2 emissions profile of concrete, asphalt and steel, and have positioned 2025 as a turning point for procurement terms applicable to federally funded transportation and building work.
The Federal Highway Administration took a big step late last year certain to impact material specification for pavement, bridge and other heavy/civil structures, and likely to parallel similar action for General Services Administration projects. FHWA published the driving metric—global warming potential (GWP), measured in kilograms of carbon dioxide equivalent per cubic yard (kgCO2e/yd.)—attending nine concrete mix classes specified for cast-in-place or precast transportation pavements, elements and structures. Posted at www.fhwa.dot.gov/lowcarbon, the Concrete Thresholds tables provide GWP data that Low Carbon Transportation Materials (LCTM) Grants recipients require to meet Environmental Protection Agency criteria. Congress tasked EPA with such oversight as part of the Inflation Reduction Act (IRA), the LCTM funding source. The IRA offers up to $2 billion in project assistance grants to state departments of transportation and non-state applicants.
An FHWA Tech Brief, Development and Use of Embodied Carbon Benchmarks for Setting GWP Thresholds for the LCTM Grants Program, details the central nature of carbon metric reporting linked to project funding. FHWA presents grant candidates two options to identify or develop GWP threshold values in accordance with an EPA advisory issued shortly after the IRA’s 2022 passage. The latter agency aims to provide “actionable determinations on selecting materials and products that meet [Act] standards [to] reduce greenhouse-gas emissions of federally funded building, infrastructure and construction projects, with a particular emphasis on reducing major industrial emissions from production of U.S. construction materials and products. This determination will support agencies in quickly beginning to use IRA resources and help the EPA glean lessons for IRA program development. The EPA may also share this determination with other agencies in the interest of supporting consistency on interpreting ‘low-embodied, greenhouse-gas emissions’ materials and products.”
EPA proposes GWP rankings and percentiles for LCTM grant project materials or products. Per IRA language, the agency interprets “substantially lower” as a GWP metric that is in the best performing 20 percent. If no materials or products in the top 20 percent are available in a project’s location, the threshold for funding opportunity shifts to 40 percent or a figure besting an estimated industry average for a material or product.
Based on National Ready Mixed Concrete Association’s Industry Average Environmental Product Declaration for Ready Mixed Concrete, FHWA Concrete Thresholds tables present GWP figures for 2,500 to 8,000 psi normal weight and 3,000 to 5,000 psi light weight concrete in eight U.S. regions. Each region has average, 20th percentile and 40th percentile GWP figures, consistent with EPA criteria for LCTM project grant approvals. Across a set of 216 thresholds, the GWP figures range from a low of 146.13 kgCO2e/yd. for 2,500 psi normal weight concrete to 478.12 kgCO2e/yd. for 5,000 psi light weight concrete, both in the Pacific Northwest Region 20th percentile columns. The regional breakdown enables EPA and LCTM grant candidates to factor GWP variations indicative of cement and aggregate production methods and quality.
While the IRA has a limited pool of funds relative to overall federal and state transportation construction funding, the LCTM Thresholds tables provide ready mixed and manufactured concrete producers a template suiting future mix design and project submittals.