The staff at the California Air Resources Board (CARB) is asking for help.1 They are under a legislative mandate2 to reduce the carbon intensity of building materials in California by 40 percent by 2035, and they are not sure how to do that. Truth be told, it may be that no one does, at least yet. While building decarbonization has long been recognized as a core imperative in California's comprehensive climate strategy, the core of this effort – embodied carbon – is a relatively new concept. So new, in fact, that it is never even mentioned in California's climate "Bible," the Scoping Plan that underwent its most comprehensive update and revision in 2022.3
Stepping back, California's climate strategy is economy-wide. CARB has identified major greenhouse gas (GhG) emission sources by economic sector and allocated a percentage of the existing emissions load to each. According to the Scoping Plan, the top emissions sector is transportation at 40 percent, having recently surpassed power generation. According to a different attribution and calculation cited by CARB staff, building operations account for 28 percent of global emissions and building materials and construction contribute 11 percent.4
Previously, California's strategy for building decarbonization, per the Scoping Plan, focused on energy efficiency, electrification of new and existing buildings, and the elimination of any reliance on natural gas in new construction.5 But more recent analysis claims that 50 percent of a building's life-cycle carbon intensity is established and locked upon construction, prior to commencing intended operations.6 Accordingly, the legislature and governor have directed CARB to reduce the carbon intensity of buildings at the construction stage and not wait for greater operational efficiency. "Embodied Carbon," defined by CARB as "the carbon dioxide equivalent emissions associated with a product as determined using life-cycle assessment,"7 is now a primary focus.
A "life-cycle assessment" (LCA), according to CARB, is a "compilation and evaluation of the inputs, outputs, and the potential environmental impacts of a product system throughout its life cycle (e.g., from cradle to grave)."8 An Environmental Product Declarations (EPD) is "a document that communicates the life-cycle assessment of a product based on defined rules," according to CARB.9 An EPD is not unlike a "Nutritional Facts" label on food products. But rather than disclosing carbohydrates and calories in a particular ingredient in a recipe, it discloses information such as embodied carbon and toxicity. The total LCA of a construction project is the sum total of the quantities disclosed in the EPD for each and every material involved in that construction project. The problem is, very few EPDs for conventional construction materials exist.10
But as energy efficiency standards and building electrification progress, reducing embodied carbon becomes increasingly essential in meeting California's targets. Presently, according to CARB, the carbon intensity of a typical commercial building is 54 percent operational and 46 percent embodied. Residential construction, on the other hand, is 41 percent operational and 59 percent embodied.11
Pursuant to AB 2446 and AB 43, both authored by Assemblymember Holden in 2022 and 2023, respectively, CARB is subject to three legislative deadlines on its road to reducing embodied carbon in building materials for both residential and commercial construction projects statewide.
- By December 31, 2026, CARB must adopt a framework for measuring carbon intensity of building materials;
- By December 31, 2028, CARB must develop a comprehensive strategy to reduce GhG emissions; and
- By December 31, 2035, CARB must achieve a forty percent reduction in GhG emissions of building materials.12
But to demonstrably show you have cut 40 percent of something, one must first know the quantification of the baseline from which one is making such a cut. And CARB has no idea how much carbon is currently embodied in the stockhold of building materials currently used by developers of all kinds in California. This is the first reason CARB staff is actively soliciting the input of developers and producers and manufacturers of construction materials on estimating the baseline of the carbon intensity of the universe of existing building materials. Critical existing data gaps according to CARB staff include: comprehensive facility-specific EPDs; quantities of material and products used for new construction; supply chain details for products and materials; costs of manufactured products; and "GhG mitigation interventions available to manufacturers and project developers."13
AB 2446 and AB 43 are not the only active measures seeking to decarbonize the building sector in California. Effective in July 2024, the Building Standards Commission adopted revisions to the California Green Building Code, CALGreen, that mandate new embodied carbon standards for large commercial construction projects. For new construction or retrofitting/demolition of existing buildings over 100,000 square feet, the project must demonstrate one of three criteria: reuse of at least 45 percent of the original structure, construction utilizing select low-carbon building materials as certified by CARB, or conducting an LCA on the building demonstrating it is at least 10% better in terms of emissions than similarly situated buildings.14
Developers and owners of buildings have grown familiar with increasing energy efficiency standards, sourcing renewable energy generation, and even efforts to ban natural gas infrastructure and appliances in new construction. But the focus on embodied carbon is a relatively new frontier, not only for the regulated community but for the regulators themselves. It remains to be seen how cooperative and collaborative the development community intends to be with CARB in advancing a new regulatory regime with which they will soon have to comply.
Footnotes
1 Survey request for development projects: https://forms.office.com/Pages/ ResponsePage
aspx?id=7qrlnYh3sUCkOMDMyYyHzCIsYYUOROFDn5QQ2UGuslJUNVZSNkhYSDdNN0E2QVdWSTlUU0hKV1c3QyQlQCN0PWcu&
utm_medium=email&utm_source=govdelivery.
Survey request for building material manufacturers: https://forms.office.com/Pages/ResponsePage
aspx?id=7qrlnYh3sUCkOMDMyYyHzCIsYYUOROFDn5QQ2UGuslJUREFRTFRDSFgxNVlZQVROS0QzR0ZBMllWRCQlQCN0PWcu&utm_
medium=email&utm_source=govdelivery
2 AB 2446 (Holden – 2022): https://leginfo.legislature.ca.gov/faces/ billTextClient.xhtml?bill_id=202120220AB2446 AB 43 (Holden – 2023): https://leginfo.legislature.ca.gov/faces/ billNavClient.xhtml?bill_id=202320240AB43
4 CARB, "Embodied Carbon in Buildings, Workshop 1," September 19, 2024 (Staff Report), slide 14 https://ww2.arb.ca.gov/sites/default/ files/2024-09/Building%20Embodied%20Carbon%20September%20 2024%20Workshop%20Final%20with%20Poll%20Results.pdf
5 Scoping Plan, pg. 212.
6 Staff Report, slide 16.
7 Id., slide 50.
8 Id.
9 Id.
10 Id., slide 50.
11 Id., slide 16.
12 Id., slide 12.
13 Id., slide 24.
14 https://www.dgs.ca.gov/bsc/calgreen
Originally published by Riverside County Bar Association
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