News Brief

Marin County First to Adopt Low-Carbon Concrete Code

A California county has the first code to address both concrete performance and concrete’s carbon emissions.

In November, California’s Marin County adopted the world’s first building code that limits carbon emissions from concrete. (Concrete’s Portland cement content accounts for more than 6% of anthropogenic carbon emissions.) The code focuses on concrete performance, creating standards for composition that “maintains adequate strength and durability for the intended application” while reducing embodied carbon, according to the county website.

The code covers both residential and commercial construction and includes standards for a number of industry practices, including:

  • replacing Portland cement with supplementary cementitious materials (such as fly ash, slag, and ground glass)
  • minimizing the amount of cement in mixes
  • selecting aggregate
  • changing the requirements for how quickly concrete has to cure (which impacts the amount of cement used)

The code still allows the use of higher amounts of cement where that performance is needed.

The County of Marin Low Carbon Concrete Code only covers concrete placed in the local jurisdiction. It does not cover precast or concrete masonry units, nor other high-carbon materials such as steel, glass, or insulation. But the code lays the groundwork for research into other avenues for developing low-carbon concrete and has the potential to be adopted by other regional, state, or national code bodies and standard developers.

Development of County of Marin Low Carbon Concrete Code was funded in part by the Bay Area Air Quality Management District Climate Protection Grant Program and developed through a partnership that includes government, engineers and architects, academia, and the Carbon Leadership Forum, along with support from the U.S. Green Building Council (USGBC), the concrete industry, and other regional stakeholders.

Published January 7, 2020

Ehrlich, B. (2020, January 7). Marin County First to Adopt Low-Carbon Concrete Code. Retrieved from https://www.buildinggreen.com/newsbrief/marin-county-first-adopt-low-carbon-concrete-code

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Comments

January 13, 2020 - 8:45 pm

Thank you for a well done article, Brent.  A few clarifications:

1) The code allows compliance by maximizing cement content (not minimizing), but also provides more sophisticated compliance paths using Environmental Product Declarations (EPDs).

2) As the author of the code language and companion documents, I wasn't aware of any support from the USGBC, but the Ecological Building Network (EBNet) was the prime instigator for the project.  Special shoutouts to Kate Simonen of the Carbon Leadership Forum, and Frances Yang of Arup Engineers.

January 14, 2020 - 11:39 am

If the embodied emissions are produced by the energy used in the cement making process, why can't those energy source be made greener, avoiding the problem as, for example, the aluminum industry is doing?

January 16, 2020 - 8:18 pm

About half the emissions from cement are from the chemical reaction that occurs when limestone is heated to turn it into the main component of cement.  I don’t believe many cement kilns are electric, though I’ll bet some in the industry are working on that.  There is also exciting progress in utilizing the kiln emissions to make aggregate that can go in concrete.  In the meantime, this policy was about reducing demand for cement as we tend to use more than really needed.  Kind of like getting more energy efficient while cleaning up the grid.
 

Thanks for the shout out Bruce! And for your vision that put it all in motion. Side note to your first point, I think Brent meant “minimizing” as in we want to minimize, while you mean “maximizing” as in we set maximums in the code.

Excited for this to spread to other jurisdictions - who will be next??!