A Proposed Methodology for Assigning Industry-Average GWP Values for Steel, Mineral Wool, and Flat Glass in California
Calculating industry-average values using EPDs, as required by Buy Clean California Act (BCCA), is challenging: the quality and quantity of data available varies by product type and is continually growing. Developed independently, the CLF team arrived at similar conclusions to those found by CA DGS when interpreting how to set limits based on California’s policy language and the current state of available data. We hope that continued development of data and refinement of limits will ultimately enable deeper embodied carbon reductions through the use of procurement policies.
The Buy Clean California Act requires the California Department of General Services (DGS), in consultation with the California Air Resources Board, to establish maximum acceptable global warming potential (GWP) limits at industry-average for structural steel (hot-rolled sections, hollow structural sections, and plate), concrete reinforcing steel, flat glass, and mineral wool board insulation (heavy and light). DGS is directed to set these limits at the industry average using data from facility-specific environmental product declarations (EPDs) or industry-wide EPDs based on domestic production data.
In order for GWP limits to be effective they must be scientifically derived, transparent in their underlying methodology, and clear in scope and definition. Calculating industry-average values using EPDs, as required by the BCCA, is challenging: the quality and quantity of data available for calculating GWP limits varies by product type and is continually growing.
The goal of Buy Clean California Limits: A Proposed Methodology for Setting Industry-Average GWP Limits for Steel, Mineral Wool, and Flat Glass is to propose industry-average GWP values for eligible materials under BCCA using a methodology that meets the following criteria:
- meets the requirements and intent of the BCCA;
- is representative of typical manufacturing production;
- is constrained to high quality, published LCA data sources that are available as of December 2021.
The research team working under direction of the Carbon Leadership Forum at the University of Washington College of Built Environments:
- Stephanie Carlisle, Senior Researcher, Carbon Leadership Forum
- Brook Waldman, Researcher, Carbon Leadership Forum
- Mikaela DeRousseau, Building Transparency
- Lianna Miller, Trisight Engineering
- Benjamin Ciavola, Trisight Engineering
- Meghan Lewis, Senior Researcher, Carbon Leadership Forum
- Kate Simonen, Executive Director, Carbon Leadership Forum
Author contributions: S.C. and K.S. led conceptualization; M.D., L.M., B.C., conducted research and analysis; S.C., B.W., M.L., and K.S. performed review and editing; S.C., B.W., M.D., L.M., B.C. and M.L. wrote the paper.
This research was funded by the ClimateWorks Foundation. We would like to thank Amlan Mukherjee and Jordan Palmeri for providing review.
Buy Clean California Limits: A Proposed Methodology for Setting Industry-Average GWP Limits for Steel, Mineral Wool, and Flat Glass is licensed under a Creative Commons Attribution 4.0 International Licence.
Carlisle, S., Waldman, B., DeRousseau, M., Miller, L., Ciavola, B., Lewis, M., and Simonen, K. (2022). Buy Clean California Limits: A Proposed Methodology for Setting Industry-Average GWP Limits for Steel, Mineral Wool, and Flat Glass. Carbon Leadership Forum, University of Washington. Seattle, WA. http://hdl.handle.net/1773/48600
Version: February 16, 2022