The Path to Low Carbon Concrete; Tracking the Proposals
- By: admin
- On: 05/09/2023 19:19:35
- In: Legislation
There are currently many different international, federal, state, and even local standards and proposals regarding what constitutes low carbon concrete. What we have found is that each agency seems to be developing its own definition or setting its own standard. Most commonly, these seem to be either a target, such as a global warming potential (GWP) number, a reduction from a threshold, or use of specific supplementary cementitious materials (SCM). Here is a summary of some of the things happening.
NRMCA Regional Numbers
To begin, the most relevant known GWP numbers for ready mixed concrete in the U.S. are in the National Ready Mixed Concrete Association's (NRMCA) 2022 Life Cycle Assessment report (version 3.2), which breaks down GWP numbers by geographic region of the U.S. The numbers are based on EPDs developed by concrete producers in the U.S. and Canada, using the National Sanitation Foundation's (NSF) International Product Category Rules, and surveys of producers. They are Type III EPDs and available for public review.
The NRMCA report places California in the Pacific Southwest Region, which includes California, Arizona, and Nevada. The latest report shows that for a standard 4,000 PSI concrete mix in the region, the average GWP is 247 kg CO2e.
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. An initiative of President Biden's, it is a partnership of the U.S. Departments of State, Energy, and Commerce, and the World Economic Forum. It is a coalition of large companies that are committed to spur the commercialization of emerging technologies to achieve substantial carbon reductions for specific products and sectors. It initially only applied to steel, trucking, shipping, and aviation, but at the Nov. 22 COP27 in Sharm-el-Sheikh in Egypt, cement and concrete were added to the list.
For cement and concrete, the commitment is for purchasers and specifiers of cement and concrete to meet a 10% volume target for near-zero cement and/or concrete, including with the use of supplementary cementitious materials, by 2030. After 2035, they would 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.
General Services Administration
In early 2022, and then updated in Sept. 2022, the General Services Administration (GSA) came up with GWP thresholds for concrete mixes used on their projects, including federal buildings and ports of entry. For their projects, a 4,000 PSI mix would have to meet a target of 346 kg CO2e/m3.
Inflation Reduction Act & US EPA
The Inflation Reduction Act (IRA) requires the U.S. Department of Transportation (DOT) and GSA to spend their funds on materials that have “substantially lower levels of GHG…” To assist these agencies, in December 2022 U.S. EPA issued interim guidance to the DOT and GSA on how to address lower carbon materials for federal projects. It says that for concrete 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 or products in the top 40%. They say comparisons can be based on averages derived from EPDs in a region, or use the NRMCA's regional GWP report.
The IRA also requires the U.S. EPA to generally recommend ways to identify and label substantially lower greenhouse emissions for construction materials, which may include recommended GWP levels. A solicitation was sent for input in January and closed on May 1. While it is unknown what U.S. EPA will recommend or exactly when, it can be expected their recommendations will be influential.
Dept. of General Services / Buy Clean California Act (BCCA)
In 2017, California enacted the Buy Clean California Act to govern state purchases of materials. Specifically, it requires material producers to submit environmental product declarations 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. While concrete has not been added to the BCCA, it likely will be at some point. Of course, it is unknown what GWP level would be set, although presumably it would be the most 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 among the materials.
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 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 do this, creating Low-Carbon Concrete requirements. They set a target of 313 kg CO2e/m3 for 4,000 PSI concrete to be low carbon. Other cities are also looking to follow the Marin model.
So, while not exhaustive, those are many of the proposals and reference points at this time. Below is a table to summarize: