Reducing Embodied Carbon

By Luke Carothers

It is no secret that the AEC industry is responsible for a significant portion of greenhouse gas emissions on a yearly basis.  Building operations are responsible for 27 percent of the world’s CO2 emissions per year, with an additional 13 percent coming from embodied carbon within construction materials.  Representing the emissions generated throughout the full life cycle of a material–including its sourcing, fabrication, installation, maintenance, and end-of-life phases–embodied carbon is a key factor to consider when trying to reduce the industry’s carbon footprint.  To help reduce this outsized embodied carbon footprint, AEC firms can utilize material selection and data.

When breaking down embodied carbon within new buildings, their structure can account for about 50 percent of their overall embodied carbon footprint.  As the two most commonly used structural materials in the building industry, concrete and steel are the two primary embodied carbon contributors.  According to Matthew Post, PE, Associate and Structural Engineer at STV, concrete is a significant contributor due to the carbon-intensive production process of its key component: cement.  Post further adds that, despite making up only a small portion of concrete mixtures by volume, the manufacturing process of cement can account for up to 90 percent of the embodied carbon footprint of concrete.  Steel, on the other hand, carries a large portion of buildings’ embodied carbon footprint due to the processes involved in extracting raw materials and converting them into usable steel.  

However, Post points out that, despite the high embodied carbon footprint associated with producing these two main materials with which we construct most of our buildings, there are opportunities to improve the environmental impact of these processes.  For example, when creating concrete mixtures, fly ash or slag–which are natural byproducts of other manufacturing processes and have a lower embodied carbon footprint–can be specified to replace a portion of the cement volume to create a more environmentally friendly mix.  Likewise, similar opportunities exist within the production of steel members, which are fabricated using either a Basic Oxygen Furnace (BOF) or an Electric Arc Furnace (EAF).  Of these two processes, the EAF is more environmentally friendly and “significantly reduces the embodied carbon footprint of steel compared to the BOF process,” said Post.

According to Lauren Alger, PE, ENV SP, the first step for firms towards reducing their structural embodied carbon footprint involves specifying more sustainable ways to fabricate materials.  Alger, the Director of Sustainable Design at STV,  further adds, “SE 2050 provides extensive specification guidance for both materials and whole-building processes.”  This includes strategies such as a general requirement to submit Environmental Product Declarations (EPDs) to evaluate and compare material footprints, or more specific directives and restrictions related to factors like recycled content or cement usage.

More than “new building” approaches to reducing embodied carbon, Alger and Post believe that firms can make a conscious effort to reuse existing buildings or building components when projects allow it.  Perhaps the most environmentally friendly option available, reuse projects avert the embodied carbon associated with new building materials as well as the demolition, removal, and post-processing of existing materials.  STV is a leading firm in supporting reuse projects, having worked to support renovations and historic preservations of transportation, education, healthcare, justice, corporate, industrial, and other facilities.  

STV is also leading the way through their involvement in programs like the Structural Engineering Institute’s SE 2050 Challenge, which requires organizations to enact an embodied carbon action plan within the first six months of signing the commitment and to submit their structural embodied carbon data to the SE 2050 project database.  STV has been very active in the SE 2050 challenge thus far, and, according to Alger, participates by regularly attending member meetings and presenting on the program’s goals and findings to promote education and awareness.  

STV’s dedication to reducing embodied carbon is further exemplified through their performance of structural analyses and research “in an attempt to find key trends related to embodied carbon.”  In this pursuit, STV recently designated four pilot projects, each designed with several variations of primary materials and structural systems.  Post says they are hoping this research teaches them more about their projects’ largest contributors to embodied carbon.  

STV has also been developing their own SE 2050 Carbon Dashboard and database, which will help track carbon emissions and visualize project data, and in turn highlight effective structural analyses across various metrics.  According to Alger, “this tool compiles the findings from our research and pilot projects, so that we can eventually publish best practices and promote efficient data tracking methods.”

As the AEC industry looks to reduce its embodied carbon footprint in the future–particularly when it comes to buildings’ structural elements–one of the biggest challenges standing in the way is a lack of proper education or awareness, according to both Post and Alger.  The need to reduce embodied carbon is evident and there are several simple tactics that can significantly help, but Alger and Post believe that a lot of this knowledge simply hasn’t been spread around the industry yet.  By spreading awareness and promoting widespread adoption of new developments and innovations in materials and technologies that can help limit embodied carbon, the cost and caution around these new materials and processes can be reduced.  Leading this effort from the front, STV is continuously advocating for and implementing creative embodied carbon solutions, helping clients and structures overcome some of embodied carbon’s leading challenges.