Buy Clean California - GWP Limits Published

After several years of phasing in Buy Clean California, the GWP limits that will come into effect on July 1 2021 have been published! These limits are for:

  • structural steel (hot-rolled sections, hollow structural sections, and plate)
  • concrete reinforcing steel,
  • flat glass, and
  • mineral wool board insulation.


I am new to the legislation aspect of embodied carbon! Is there a reason why concrete mix designs are not included in this Act?

Hi Alexis. Originally cement was targetted for inclusion, but industry pushed back making the argument that the product is ‘trade-exposed’ meaning that purchasers could easily change to buying lower-carbon imported cement only and the local California-based cement industry could collapse. The validity of the argument, and if it’s applicable to other included materials too, can be challenged. However, their argument won the day and it was excluded from this initial version of the Act. The state has said that they intend to expand the list of eligible materials covered in the future, which would presumably include cement in the future.

Note that Portland, Oregon has a Low Carbon Concrete procurement policy which is effectively Buy Clean only for concrete.

Ryan, I appreciate the response. And thank you for pointing me to the Portland requirements.
Hopefully the cement / concrete suppliers will be more open in the future and evolve mix designs alongside engineers.

Great question on Concrete! In addition to the Portland policy that Ryan shared, I would also mention the Low Carbon Concrete Project - County of Marin and the new bill HB 1103 introduced in Washington State Legislature, which includes concrete, steel, and wood. Similar bills are being considered in other states as well - check out our new map to track!

1 Like

I’m reading the notes and it seems they took industry averages and then added 15-35% to set an upper limit. So this is aimed at excluding worst performers. I suppose it’s a first step but doesn’t seem like it will push things a lot. Do you know if it will be reassessed as the industry average changes?

1 Like

In terms of updating, the current legislation requires that Beginning on January 1, 2024, and every three years thereafter, DGS will review the maximum acceptable GWP for each material and may adjust the limit downward to reflect industry improvements."

The legislation also prohibits the limits from moving upward if the average gets worse (let’s hope not!!) but there is no required trajectory to lower the limits towards net-zero.

The FAQ section in the same DGS page where these limits were published is great! Answer to lots of questions like this: Buy Clean California Act

Question: why mineral wool? Why not XPS, for instance?