Thinking outside the (operational) box: The missing piece of embodied carbon

Our industry is engaged in an important dialogue to improve sustainability through ESG transparency and industry collaboration. This article is a contribution to this larger conversation and does not necessarily reflect GRESB’s position.

Approximately 40% of the world’s annual greenhouse gas (GHG) emissions are attributed to the built environment. With the global building floor area expected to double by 2060, this impact must be addressed with greater urgency and perspective. Numerous policies, regulations, and initiatives are being passed and implemented, globally, to address the built environment’s impact and carbon emissions. However, most of these policies and ways of thinking revolve only around operational carbon. We need to be thinking bigger!

Operational emissions are the total emissions released from the generation of non-renewable energy used to operate a building or piece of infrastructure, through end-uses such as heating, cooling, ventilation, lighting, appliances, and plug loads. Operational carbon accounts for about 27% of global emissions.

Because it is tied to energy uses that we can easily measure, the general visibility of operational carbon has accelerated the creation of tools and methods for tracking and making reductions. Other sources of GHG emissions, comparatively, have not yet gained this level of visibility and thus have been more difficult to address. Here are a few examples of reduction efforts developed to address operational carbon, which have been made possible by its visibility:

Energy codes and standards requiring increased energy efficiency
Renewable energy procurement to directly replace fossil fuel usage
Energy data management platforms allow for continuous monitoring
Data standardization & KPI’s
Energy audits provide direct measurement tools
Accountability by attributing emissions to specific occupancy factors, activities, spaces, and owners

Many existing Building Performance Standards and regulations focus solely on operational emissions which provides methodologies and structure to inform decision making. In New York City (NYC) for example, Local Law 97 establishes operational emissions caps for most buildings larger than 25,000 square feet. The law applies to nearly 50,000 buildings across NYC. While the carbon limits were set in May 2019, the first compliance reports are due in May 2025. The carbon limits are set to become more stringent over a series of compliance periods, with the goal of contributing to citywide efforts to reduce GHG emissions 80% by 2050. This law, while aimed at addressing 40% of global GHG emissions coming from the built environment, applies only to operational emissions.

The emphasis on and development of strategies to address operational carbon— while important, overlooks another significant source of carbon— embodied carbon. Of the 42% of the world’s annual carbon emissions coming from buildings, one-third is attributable to embodied carbon. With the current focus and flow of climate action, the significant impact of built environment emissions is only partially being addressed. A big piece of the puzzle is missing!

What is embodied carbon?

Embodied carbon includes, at a minimum, the GHG emissions produced during the upstream stages of a product’s life cycle, such as extraction, production, transport, and manufacturing. However, organizations and initiatives, such as the United Nations Environment Programme (UNEP) and the World Green Building Council’s (WGBC) “Bringing Embodied Carbon Upfront,” go even further to include emissions through the product’s entire lifecycle, as shown in Figure 1 (below). This perspective takes a more progressive approach, embracing aspects of circularity such as life cycle assessment and resource optimization. To complete the puzzle of GHG emissions in the built environment, the contributions of embodied carbon through the product lifecycle must be included.

The concept of embodied carbon is relatively recent in the building industry and in recognizing environmental impact globally. Examples of embodied carbon sources include the extraction of limestone used to make concrete, the energy used to create glass, the transportation of building materials to a construction site, and the carbon released during the demolition or disposal of building materials.

Figure 1. Terminology cross-referenced to terms and life cycle stages defined in EN15978. (WGBC)

Mitigation and reduction strategies: Puzzled over where to start?

The majority of embodied emissions generated from materials of buildings and infrastructure originate during the product phase (65-85%), making it the most critical phase to start addressing (Figure 2). Additionally, in the next 10 years, Architecture 2030 estimates that 80% of the total GHG emissions produced from new buildings will come from embodied emissions. This high percentage is partly attributed to the expected reductions in operational carbon, due to the responses detailed above. But stresses the importance of lowering embodied emissions and addressing carbon holistically, which starts with the heavy hitting “product phase”.

Figure 2. Embodied Carbon throughout Life-Cycle Assessment Phases. (RMI)

Currently, there is not a universal threshold for ‘low embodied carbon’ materials, but task forces and creative ideas are being circulated. In the United States, the Federal Buy Clean Initiative is underway, and in Europe, “raw earth” construction materials (a catchall term for building materials that primarily consist of soil and are not baked into a hardened state), are being resurfaced as an alternative option for specific types of construction emitting significantly less embodied carbon than traditional materials (i.e., a 50% or more reduction). Earlier this year, the first application of a low-carbon cement took place during the construction of One Wharf Boston, Boston’s largest net-zero-carbon office. By utilizing electrochemistry to extract the ingredients needed, this innovative approach avoids the major emission sources typically associated with traditional cement.

Additionally, there are strategic methods and frameworks in development that focus on reducing embodied carbon, especially in the product phase, some of which include Life Cycle Assessments (LCA), Environmental Product Declarations (EPD), and Leadership in Energy and Environmental Design (LEED).

LCA: An LCA is an analytical method that assesses the environmental impact of products and services. The LCA helps identify where the most significant embodied emissions occur which can help inform product design decisions and set realistic carbon reduction efforts.
EPD: An EPD is a standardized document that provides transparent, comparable information about a product’s environmental impact based on LCA data. The ‘single-company, single-property’ EPD is the most used type of EPD, which focuses on a specific product’s footprint. EPDs are a great tool to help identify products with lower embodied emissions upfront.
LEED: LEED’s Building Design and Construction’s (BD+C) latest iteration, LEEDv5, launches in 2025 and strongly focuses on lower embodied carbon (LEC) approaches and addressing carbon-intensive materials. LEED incorporates LCAs and EPDs as methods to earn credits. Engaging with LEEDv5 will be a powerful tool in creating an ultra-low-carbon building.

All these strategic methods and frameworks contribute to an increased understanding of emissions in the product phase and reducing the overall embodied emissions of a product or service.

Reuse: New perspective, not product!

The strategies above highlight ways to reduce embodied carbon from a product’s start, but there is also an impact that can be made downstream. While the choice of building materials can significantly impact the carbon footprint of a building, what happens to the material during renovation or demolition of a building? The current industry trend is to replace old materials with similar new ones. New materials go through the extraction, manufacturing, and delivery phases—just to end up at the same stage as the previously used material. All for Reuse , an initiative engaging with building professionals to embrace material reuse options, is bringing awareness to the topic by spotlighting how building materials reuse is an overlooked solution to embodied carbon reduction. All for Reuse’s data shows that material reuse offers 99% or more embodied carbon reduction (Figure 3). Reuse strategies can propel the building industry towards a circular economy by maximizing the use of a product while simultaneously limiting the carbon footprint of a building.

Figure 3. All For Reuse poster explaining the embodied carbon benefits of reusing materials. (All For Reuse)

Stakeholder collaboration and innovation

Typically, operational carbon has been addressed in a siloed manner, often relying solely on one responsible party (i.e., MEP) and excluding other stakeholder groups. In contrast, the circular nature of embodied carbon necessitates collaboration to effectively achieve impact. This type of engagement brings together experts across fields, including architects, engineers, designers, builders, policymakers, etc. Bridging the communication gap across these fields will accelerate change and help address all built environment emissions.

Putting the pieces together: The future with embodied carbon

To put the puzzle of carbon impact in the built environment together, we need to address a critical missing piece—embodied carbon. The development and visibility of operational carbon is a great resource to inspire and drive change related to embodied carbon. We are headed in the right direction with more stringent policies like LL97, but we need to push for new policies to include embodied carbon as well. Continued engagement with strategies for quantifying and reducing embodied carbon referencing initiatives, like All for Reuse, and using LCA, EPDs, and LEED, is also crucial in piecing together this puzzle. All for Reuse is reimagining how we use and value materials. LCAs and EPDs are helping establish a baseline for embodied emission calculations. LEEDv5 is set to drive innovation in material production and foster transparency across the supply chain. These strategies are all good starts, but there is more work to be done! We can start by increasing engagement with stakeholders, learning from recent industry successes, and finding ways to leverage methods initially developed for addressing operational emissions to combat embodied emissions. Specifying low-carbon-emitting new materials or repurposing existing materials should be a focus for all new construction projects. The more our communication, strategy implementation, and shared innovations can include embodied carbon, the greater impact we can have in addressing the overall carbon impact of the built environment. And with the built environment continuing to grow, addressing embodied carbon is the key to completing the emissions puzzle and seeing the whole picture.

This article was written by Paige Karl, Sustainability Analyst at CodeGreen.

References:

“All for Reuse, Concept Paper.” All for Reuse. Accessed October 28, 2024.

Gehrung. “All for Reuse’ looks to cut embodied carbon.” Building Green. Accessed October 28, 2024.

“What is Local Law 97?” Urban Green. Accessed 10/28/2024

“Why making buildings greener is crucial to countering climate change .” UNEP. Accessed October 28, 2024.

“Life Cycle Asessment.” Science Direct. Accessed October 28, 2024.

Weir et al. “How “Embodied Carbon 101: How to eliminate the emission hidden in concrete. steel, insulation, and other building materials.” RMI. Accessed October 29, 2024.

“Bringing Embodied Carbon Upfront .” World Green Building Council. Accessed October 29, 2024.

“Environmental Product Declaration (EPD) – The complete guide .” Ecochain. Accessed October 29, 2024.

“Different EPD Types .” EPD. Accessed October 29, 2024.

“EPD creation explained in 5 simple steps .” EPD. Accessed October 29, 2024.