The Path to Low Carbon Concrete: Tracking the Proposals
Originally posted May 9, 2023. Updated as of June 14, 2023
There are currently many different international, federal, state, and even local standards and proposals regarding what constitutes low carbon concrete. Each agency seems to be developing its own definition or setting its own standard. Most commonly, these seem to be a global warming potential (GWP) target, or a reduction from a threshold. Here is a summary of some of the things happening.
NRMCA Regional Numbers
To begin, the most data-driven GWP numbers for ready mixed concrete in the U.S. are in the National Ready Mixed Concrete Association's (NRMCA) report, “A Cradle-to-Gate Life Cycle Assessment of Ready Mixed Concrete Manufactured by NRMCA Members – Version 3.2,” Dec., 2021. It is based on collection of publicly available Type III environmental product declarations (EPD) from concrete producers in the U.S. and Canada. The NRMCA report is divided into regions of the U.S. It places California in the Pacific Southwest Region, along with Arizona and Nevada. The latest report shows that for a standard 4,000 PSI concrete mix in the region, the average GWP is 323 kg CO2e/m3.
Despite this regional breakdown, the Southwest region remains a large area, with very diverse geography, climate, and materials within it. Notably, too, with each passing year the GWP numbers get lower as producers incorporate more ways to use less impactful materials and make their operations more efficient. As can be expected, it is based on only the operators that have developed EPDs or participated in surveys, so most likely the ones doing the most on sustainability. Furthermore, the data can't account for regional differences within a state, which is particularly important in a state as large and geographically diverse as California.
First Movers Coalition
At the UN Climate Change Conference (referred to as COP26) in Glasgow, Scotland in November 2021, the First Movers Coalition was announced. It is a partnership of the U.S. and the World Economic Forum. Participants are primarily large companies that have committed to purchasing and other requirements for lowering carbon impacts. Initially, it only applied to steel, trucking, shipping, and aviation, but cement and concrete were added at the Nov. 22 COP27 in Sharm-el-Sheikh in Egypt.
The commitment is for purchasers and specifiers of cement and concrete to, by 2030, meet a 10% volume target for near-zero cement and/or concrete. After 2035, they could not use fossil-based SCMs to achieve the target. The target level was developed by the Concrete Action for Climate Initiative and Global Cement and Concrete Association. For concrete at 4000 psi, the target is 96 kg CO2e/m3.
Inflation Reduction Act & US EPA
The Inflation Reduction Act (IRA) requires the U.S. EPA to develop recommendations for lower carbon emissions from materials. These recommendations are to be used by the Federal Highway Administration and General Services Administration for IRA funded-projects. In December 2022, U.S. EPA issued interim guidance. It says the GWP should be in the top 20% (or lowest 20% in embodied greenhouse gas emissions) compared to similar materials. If the material is not available in the top 20%, they recommend materials in the top 40%. They say comparisons can be based on averages derived from EPDs in a region, or, for concrete, to use the NRMCA's regional GWP report.
The U.S. EPA continues to work on developing updated or final guidance. This will be based on data derived from GSA pilot projects (see below), input from FHWA stakeholder groups, and a public solicitation by U.S. EPA earlier this year. At this point, there is no timeline to complete this. When issued, it can be expected to be influential.
General Services Administration
Per the IRA, the GSA has initiated a pilot program for low carbon materials in IRA funded projects. It was issued in Spring of 2022, updated it in Sept. 2022, and then updated it, again, in May 2023. The most recent iteration follows the interim guidance issued by US EPA in December 2022.
The GSA's May 16, 2023 GWP limits for low embodied carbon concrete say 4,000 PSI concrete in the top 20% is 284 kg CO2e/m3; top 40% is 326 kg CO2e/m3 and “better than average limit” is 352 kg CO2e/m3.
Dept. of General Services / Buy Clean California Act
In 2017, California enacted the Buy Clean California Act (BCCA) to govern state purchases of materials. Specifically, it requires material producers to submit environmental product declarations (EPD) and for the Department of General Services to set global warming potential numbers for eligible materials. At this time, BCCA only applies to steel, reinforcing steel, glass, and insulation. Concrete has not yet been added. So, it is unknown what GWP levels would be set, although presumably they would be specific to California and its regions.
California Air Resources Board
The bill AB 2446 passed in 2022 and requires the Air Resources Board to develop ways to measure and reduce the carbon emissions in building materials by 40% by 2035. This would apply to residential, commercial, and public buildings over 10,000 sq. ft, or residential developments with more than 5 homes. It would presumably include concrete.
It requires a general framework to be developed by 2025, data collected on building materials emissions in 2026, and carbon thresholds established as early as 2027. It would require a 20% carbon reduction in materials by 2030, and a 40% reduction by 2035. Work has not actually started on this yet, and the dates may get pushed back.
CALGreen Building Code
The CALGreen Building Code is being updated to add a mandatory requirement for carbon reduction for materials used in buildings. It is called the CALGreen Carbon Reduction Collaboration, and will likely be approved this August. It would apply to buildings over 100,000 square feet beginning in July 2024, and buildings over 50,000 square feet beginning in January 2026. It will provide a wholistic design option as well as a product specific option. For concrete, the product specific option for 4000 psi concrete would need to meet a GWP target of 566 kg CO2e/m3 . This is 175% of the NRMCA regional average for the Pacific Southwest.
Several local jurisdictions in California have taken the initiative to create their own standards for low carbon concrete in their building codes. Marin County was the first to create Low-Carbon Concrete requirements. They set a target of 313 kg CO2e/m3 for 4,000 PSI concrete. Other cities also looking at similar proposals.
So, while not exhaustive, those are many of the proposals or standards. Below is a table to summarize. The different agencies' websites should be consulted for the full standard across the range of concrete strengths and types: