Clean Technica


Audrey Rempher & Victor Olgyay


It is unlikely that you know how much carbon was produced by making your driveway. But if you did, you might think about ways to build it better.

That is the concept behind the “Buy Clean Colorado” legislation signed into law July 6 by Colorado Governor Jared Polis. Under the new law, future public construction projects will have to meet clear environmental criteria for the use of seven common construction materials.

With the passage of HB21-1303: Global Warming Potential for Public Project Materials (the formal name of the Buy Clean Colorado legislation), Colorado joins a growing group of states pursuing an untapped opportunity for carbon reductions: the carbon “embodied” in public buildings and roads. With a goal to reduce emissions by 50 percent by 2030 and 90 percent by 2050, Colorado has some of the most ambitious climate goals among US states. This legislation will help the state to meet these bold targets.

What Is Embodied Carbon?

If you’ve never heard of embodied carbon, you are not alone. In the building industry, embodied carbon refers to the greenhouse gas emissions arising from the entire life cycle of a material: from manufacturing, transportation, installation, and maintenance to the disposal or reuse of building materials. Embodied carbon is typically quantified as the amount of carbon generated per unit of material. This data on the “global warming potential” of a material is documented in environmental product declarations (“EPDs”), which are analogous to the nutrition labels on food products. Through publicly accessible databases (such as the EC3 tool), anyone can access EPDs and directly compare the data to select products with low amounts of embodied carbon. 

What Is Buy Clean Colorado?

Buy Clean Colorado uses the EPD methodology to help drive the use of low-embodied-carbon materials. The bill requires the office of the state architect and the department of transportation to each establish policies that include the maximum acceptable global warming potential for specific categories of construction materials. The limits on global warming potential for these materials will apply to certain public projects, including buildings, roads, highways, and bridge projects.

The limits are expected to apply to projects solicited after January 1, 2024. The required global warming potential limits will be reviewed and adjusted every four years.

Industry Impact

By shining a light on the carbon embodied in building materials, the Buy Clean Colorado legislation will increase demand for low-embodied-carbon products. In Colorado today, materials with lower global warming potential are already available and being used. It is possible to purchase two products with identical structural and performance characteristics, but with greatly varying amounts of embodied carbon. By establishing preferential purchasing for low-embodied-carbon materials, a new class of product is defined as desirable. The construction materials industry has generally welcomed this opportunity to expand their offerings.

While there are always costs associated with product improvement, many of the low-embodied-carbon versions of construction materials come at no cost premium. Analyses by RMI and others have shown that it is currently possible to reduce the embodied carbon in building projects by 30 to 50 percent at low to no cost, simply by specifying low-embodied-carbon materials. With further design work and material substitution, it is possible to have even greater positive impact. Using materials with higher recycled content, or more localized materials that reduce the need for transportation, can reduce costs as well as embodied carbon.

LafargeHolcim, the operator of one of Colorado’s two cement plants, currently offers a low-embodied-carbon product that has been used on 600 lane miles of concrete paving in Colorado. The company testified in support of the new bill, and the Colorado Department of Transportation and other industry representatives have also been supportive. Buy Clean Colorado highlights the opportunity for construction product manufacturers that are already taking steps toward lowering their carbon footprint to see increased demand for their products.

Will It Make a Difference?

Cement is estimated to be responsible for 7 percent of global CO2 emissions. Reducing the embodied carbon in cement alone to the current cost-effective level can have an enormous impact locally and provide substantial contributions to Colorado’s ambitious climate goals. In addition, the new bill will encourage manufacturers to produce more products that have less environmental impact.

Colorado’s legislation will serve as a model for other states considering policies and codes for low-embodied-carbon materials. As the literacy around embodied carbon and EPDs becomes more widespread, you will no longer need to wonder how much carbon was produced by making your driveway. You will know, and you just may build it better.