The Emissions DNA of Building Materials: Embodied Carbon
When considering Scope 1 and 2 emissions, most people think of the impact of energy use for heating, lighting, and transportation. But for those who serve businesses focused on emissions reductions, it is not enough to focus on a building design that models a lower Scope 2 emissions profile. Ignoring embodied carbon – the emissions embedded in building materials – shortchanges the client’s efforts. This scope 3 emissions category presents mystery and challenges, not unlike human DNA. As scientists are discovering ways to hack human health through DNA discovery, developers and the AEC community are helping businesses hack their emissions profile by understanding embodied carbon.
So what is it? Embodied carbon is the carbon dioxide (CO₂) emissions from manufacturing, transportation, installation, maintenance, and disposal of building materials. Understanding all of the sources of emissions – operational and embodied – is critical for developers, particularly as the public demands more climate-conscious practices from businesses and as governments require businesses to report emissions.
To take it a step further, the World Green Building Council's research suggests that the global building stock will double by 2060. As the number of building worldwide doubles, so too will the amount of embodied carbon being placed into them. In fact, the research suggests that embodied carbon will be 50% of building-related emissions by 2050. These numbers sound an alarm that calls for developers and the AEC community to increase awareness and change practices when it comes to embodied carbon.
How Embodied Carbon is Like DNA
Analogies can make complex concepts easier to comprehend. I find thinking of embodied carbon as the DNA of building materials easier to understand. To understand a material’s embodied carbon profile, we must first consider what defines embodied carbon.
Embodied carbon is broken into two categories: upstream and downstream. Upstream consists of emissions associated with the initial construction, whereas downstream refers to maintenance during the building’s lifecycle and end of life. Upstream emissions are separated into the production and construction stages.
The vast majority of embodied carbon generates during the production stage from the extraction of raw materials. Building materials like concrete, aluminum, and steel require a constant feed of raw materials and today account for 23% of global emissions. Even though there is traditionally recycled content in each, the production relies heavily on fossil fuels. Simply stated, these materials are examples of those that lack an easy decarbonization pathway.
Embodied carbon in the construction stage primarily comes from transporting materials to the job site and construction activities (workers and equipment). Downstream embodied carbon emissions include building repairs, dismantling buildings, and end-of-life material disposal.
One of the first moves of the sustainable building industry and sustainable building rating systems was to reward projects for using materials with recycled content, that were manufactured close by, and that come from manufacturers with take-back programs. In the current version of LEED, there are optional credit points specifically that reward these material characteristics. While the term “embodied carbon” was not front and center in the initial version of LEED, the outcome of focusing on materials with regional and recycled content gave a nod to materials with lower embodied carbon profiles. The material “DNA” matters.
How Embodied Carbon is Tracked & Reported
The complexity of embodied carbon can make it difficult to calculate and track consistently. This is primarily due to the nature of self-assessment and transparency needed between partners across the value chain. However, utilizing a carbon accounting standard can help streamline the reporting process. Many materials now come with an Environmental Product Declaration (EPD), which provides a profile of the product’s embodied carbon.
Led by customer and client demand, or pushed by regulators, many companies are beginning to report their greenhouse gas emissions. Initial reports likely will focus on scopes 1 and 2, the reporting entity’s direct and indirect carbon emissions. As emissions reporting grows across industries, entities are broadening their tracking and reporting to include Scope 3. The design, construction, renovations, and maintenance of buildings are a primary source of upstream and downstream Scope 3 emissions.
For this reason, developers and the AEC industry are compelled to understand the impact building materials have on Scope 3 emissions.
Identifying Embodied Carbon with Life Cycle Analysis (LCA)
LCAs review all aspects of a project, upfront and downstream emissions, to calculate a cradle-to-grave embodied carbon estimate. This assigns a carbon value to each portion of the project to allow for easy comparison and the identification of carbon “hot spots.” Because it is conducted before construction, the insights are used to develop and implement alternative low-carbon strategies in the final project design.
Emerald recently conducted a Building Life Cycle Assessment (BLCA) for Intro Cleveland, LEED Gold Certified and the nation’s largest mass timber building. The BLCA modeled the mass timber design as 21% fewer tons compared to a baseline steel and concrete building.
How the AEC Community Can Lower Embodied Carbon
By using an LCA as the tool to evaluate material options, designers are then able to focus on implementing low-carbon alternatives in high emissions areas. While this is a project-by-project case, there are typically three main focus areas.
BUILDING MATERIALS. Materials are inherently a carbon “hot spot.” To address the embodied carbon from the manufacturing process, designers can specify products with lower profiles such as those made locally, that contain recycled content, that contain bio-based ingredients, or that are manufactured with renewable energy (among others).
TRANSPORTATION: Products shipped long distances will have a higher profile for the transportation category. Reduction strategies include sourcing closer to the job site or requiring low-carbon transportation options.
CONSTRUCTION PROCESS: Overall building and construction processes can utilize strategies to reduce embodied emissions. Options include job sites fueled by renewable energy vs. fossil fuels or advanced framing, and other material and waste reduction strategies.
It is nearly impossible to reach net zero embodied emissions. For emissions that can’t be limited by direct operational or construction change, carbon offsets can provide the final push for carbon-neutral buildings.
Responsibility For Emissions is Growing
Upstream carbon impacts are irreversible, whereas operational carbon can be analyzed and mitigated along the way. With more and more materials being produced, the upstream embodied carbon will equal operational carbon emissions over the next decade, shifting urgency to address the impact of construction alongside ongoing operations. Developers and the AEC community hold a responsibility to help achieve global emissions reductions targets while also supporting their clients in their emissions reductions goals. Using tools like building life cycle assessment and specifying lower-profile materials are the first steps. In addition, carbon sequestration and offset credits will be needed to balance the bottom line.
Emerald Built Environments is experienced in completing LCAs, evaluating building designs, and helping developers achieve green building certifications. We can help you reduce emissions in your next project and capitalize on financial incentives along the way.