Embodied Carbon in Building Materials: A Deep Dive

The construction industry has a significant impact on the environment, contributing substantially to global greenhouse gas emissions¹. While operational carbon, generated from a building's energy consumption during its use phase, has been a primary focus for sustainability efforts, embodied carbon is emerging as a critical factor in achieving a truly sustainable built environment. Embodied carbon refers to the greenhouse gas emissions arising from the manufacturing, transportation, installation, maintenance, and disposal of building and infrastructure materials². It is a significant percentage of global emissions and requires urgent action to address it². Embodied carbon can represent a significant portion of a building's total carbon footprint, especially as operational carbon decreases with energy-efficient designs. For new buildings, embodied carbon emissions typically equal about 20 years of operating emissions³. This report delves into the concept of embodied carbon, explores its impact on overall sustainability, and examines strategies to reduce its contribution to climate change.

Defining Embodied Carbon

According to the Environmental Protection Agency (EPA), "Embodied carbon refers to the greenhouse gas emissions associated with the production (the extraction, transport, and manufacturing) stages of a product's life." ⁴ In broader terms, embodied carbon encompasses all greenhouse gas emissions generated throughout the life cycle of building materials. This includes emissions from:

• Extraction of raw materials: Mining, quarrying, and harvesting activities release emissions.
• Manufacturing and processing: Transforming raw materials into building products requires energy and often involves chemical processes that generate emissions.
• Transportation: Moving materials from extraction sites to manufacturing facilities and then to construction sites consumes fuel and releases emissions.
• Construction: On-site activities, including the use of machinery and equipment, contribute to emissions.
• Maintenance: Repairing, replacing, and upgrading building components over time generate emissions.
• End-of-life processing: Demolition, waste transportation, and disposal or recycling processes release emissions³.

For example, consider the embodied carbon of concrete. The extraction of raw materials like limestone and the production of cement, a key ingredient in concrete, are energy-intensive processes that release significant amounts of CO2. Transportation of these materials to the construction site further adds to the embodied carbon footprint.

Embodied carbon is typically measured in kilograms of carbon dioxide equivalent (kg CO2e) per unit of material or per square meter of building floor area².

Embodied Carbon in Building Materials

In the context of building materials, embodied carbon refers to the total greenhouse gas emissions associated with all stages of a material's life cycle, from raw material extraction to end-of-life processing⁶. It is a crucial aspect of sustainable construction because it represents a significant portion of a building's overall carbon footprint⁷.

Impact of Embodied Carbon on Overall Sustainability

Embodied carbon has a profound impact on overall sustainability, primarily due to its contribution to climate change. The building and construction sector accounts for a substantial portion of global greenhouse gas emissions, with embodied carbon playing a significant role⁸. The extraction, manufacturing, and transportation of building materials are energy-intensive processes that release significant amounts of carbon dioxide and other greenhouse gases into the atmosphere⁹. These emissions contribute to global warming, leading to adverse environmental consequences such as rising sea levels, extreme weather events, and disruptions to ecosystems⁹. Since most embodied carbon emissions occur at the beginning of a building's lifecycle, it's essential that we reduce...source

Furthermore, the production of certain building materials can have detrimental effects on local environments and communities. For example, cement production, a major contributor to embodied carbon, is associated with air and water pollution, habitat destruction, and resource depletion¹¹.

It is important to note that embodied carbon is not just about upfront emissions during material production and construction. It also includes emissions from maintaining the building and eventually demolishing it, transporting the waste, and recycling it¹². This highlights the importance of considering the entire life cycle of a building when assessing its environmental impact.

Addressing embodied carbon in building materials is not only an act of climate mitigation but also an act of climate adaptation. By using sustainable and resilient materials, we can create buildings that are better equipped to withstand the impacts of climate change, such as extreme weather events¹³.

Moreover, reducing embodied carbon can have positive social impacts. Cleaner manufacturing processes can lead to improved air quality and community health¹⁰.

Another crucial aspect of embodied carbon is the concept of "hotspots" in the supply chain. Hotspots are points in a supply chain or a product's life cycle with the most significant environmental impacts⁷. Identifying and addressing these hotspots can be a crucial strategy for reducing embodied carbon.

Reducing Embodied Carbon in Building Materials

Mitigating the impact of embodied carbon requires a comprehensive approach that considers all stages of a building's life cycle. Here are some key strategies to reduce embodied carbon in building materials:

• Optimize building design: Efficient structural design, minimizing material use, and prioritizing building reuse or renovation can significantly reduce embodied carbon¹⁴.
• Use reclaimed or recycled materials: Incorporating materials recovered from demolition or waste streams reduces the demand for new materials and the associated emissions¹⁴.
• Specify low-carbon and carbon-storing materials: Choosing materials with lower embodied carbon, such as those made from recycled content or bio-based materials, can significantly reduce a building's carbon footprint¹⁴. For example, substituting cement with slag, fly ash, or other pozzolanic or lime-based materials can reduce embodied carbon by 14–33% at no cost or even a cost reduction¹¹. Selecting low embodied carbon insulation materials, such as using polyiso or mineral wool batt instead of XPS, can reduce embodied carbon by 16% at no cost premium¹¹.
• Source materials locally: Reducing transportation distances minimizes emissions associated with moving materials¹⁶.
• Improve manufacturing processes: Encourage manufacturers to adopt cleaner production technologies and use renewable energy sources¹⁷.
• Promote sustainable construction practices: Implement efficient construction methods that minimize waste and reduce on-site emissions¹⁷.
• Design for deconstruction and reuse: Plan for the disassembly and reuse of building components at the end of a building's life, reducing waste and the need for new materials¹⁸.
• Landscaping: Incorporating landscaping elements that contribute to carbon sequestration, such as trees and green roofs, can help offset embodied carbon emissions⁷.

Reducing embodied carbon can also offer building projects significant cost savings¹⁶. This can be achieved through optimizing the structure, reducing the quantities of high-emitting materials used, re-using building materials, selecting more sustainable, lower-carbon materials, and sourcing building materials locally¹⁶. These activities save money in multiple ways, including by avoiding the purchase of excess materials and reducing material transportation fees¹⁶.

Furthermore, to reach our climate goals, it is necessary to leverage building materials as an opportunity to sequester and store carbon¹⁰. This can be achieved by using carbon-storing materials, primarily plants like wood, hemp, straw, bamboo, and algae, that have sequestered carbon during their growth before being transformed into a building material¹⁰. This approach can shift buildings from being carbon sources to becoming carbon sinks, contributing to a more sustainable built environment.

Examples of Sustainable Building Materials with Low Embodied Carbon

Several sustainable building materials offer lower embodied carbon compared to conventional options. These include:

Policies and Regulations Related to Embodied Carbon

Governments and organizations are increasingly recognizing the importance of addressing embodied carbon in the building industry. Several policies and regulations are being implemented to promote embodied carbon reductions:

Procurement Policies

One strategy for addressing embodied carbon is through "Buy Clean" policies and programs¹⁹. These are procurement policies that establish requirements for government purchasing, with a focus on construction materials that reduce embodied carbon emissions. Buy Clean policies tend to focus on materials with the highest embodied carbon impacts: concrete, steel, and aluminum, which combine for 23% of total global emissions¹⁹. An example is the Buy Clean California Act, AB 262 (2017), which requires certain public projects to gather and disclose emissions data by producing facility-specific Environmental Product Declarations (EPDs) for high embodied carbon products¹⁹.

Building Codes and Standards

Incorporating embodied carbon requirements into building codes and green building rating systems is another important policy approach²⁰. For example, the Marin County Low Carbon Concrete Code was the first code (2020) that required all new commercial building projects to incorporate low-embodied carbon concrete²¹.

Carbon Reporting and Disclosure

Mandating the measurement and reporting of embodied carbon in building projects is crucial for increasing transparency and driving reductions¹⁹.

Prioritizing Existing Buildings

Policymakers can play a crucial role in prioritizing the reuse and renovation of existing buildings, which can significantly reduce embodied carbon compared to new construction²².

Organizations and Initiatives Focused on Reducing Embodied Carbon

Numerous organizations and initiatives are dedicated to reducing embodied carbon in construction. These include:

• Carbon Leadership Forum: A non-profit organization focused on accelerating the transformation of the building sector to radically reduce embodied carbon²³.
• Building Transparency: An organization that provides open-access data and tools to promote embodied carbon reductions in the built environment²⁴.
• New Buildings Institute (NBI): A non-profit organization that promotes energy efficiency and decarbonization in buildings, with a focus on embodied carbon²³.
• American Council for an Energy-Efficient Economy (ACEEE): A non-profit research organization that develops policies to reduce energy waste and promote clean energy, including embodied carbon in buildings²⁵.
• World Green Building Council: A global network of green building councils that promotes sustainable building practices, including embodied carbon reductions²³. The WorldGBC has issued a bold new vision for net zero embodied carbon: By 2030, all new buildings, infrastructure and renovations will have at least 40% less embodied carbon with...source carbon²⁶.

Conclusion

Embodied carbon is a critical consideration in achieving a sustainable built environment. By understanding the concept of embodied carbon, its impact on overall sustainability, and the strategies to reduce it, the construction industry can make significant strides towards decarbonization. Implementing the measures outlined in this report, such as optimizing building design, using low-carbon materials, and promoting sustainable construction practices, will be essential in mitigating the environmental impact of the built environment and contributing to a more sustainable future.

The increasing importance of embodied carbon in green building standards and voluntary certification systems, such as BREEAM and LEED, highlights the growing recognition of its significance in achieving sustainability goals²⁷. These rating systems give points for performing whole-building life cycle assessments and making reductions as compared to benchmarks²⁷.

However, addressing embodied carbon presents both challenges and opportunities. Collaboration between stakeholders in the building industry, including architects, engineers, contractors, and policymakers, is crucial for driving meaningful reductions. Technological advancements in material production and construction processes will play a key role in achieving ambitious embodied carbon targets. Embodied carbon has the potential to become a key driver of innovation in building design and construction, leading to the development of new materials, technologies, and approaches that minimize environmental impact while enhancing building performance and resilience.

Further Considerations

While this report provides a comprehensive overview of embodied carbon in building materials, further research and development are needed in several areas:

• Data availability and accuracy: Access to reliable and comprehensive embodied carbon data for various building materials is crucial for accurate assessments and informed decision-making.
• Life cycle assessment (LCA) methodologies: Standardized and robust LCA methodologies are essential for consistent and comparable embodied carbon calculations.
• Innovation in materials and technologies: Continued research and development of new low-carbon building materials and construction technologies are crucial for achieving significant embodied carbon reductions.
• Policy and market mechanisms: Effective policies and market incentives are needed to drive the adoption of low-carbon materials and practices in the building industry.

By addressing these challenges and continuing to prioritize embodied carbon reductions, the construction industry can contribute significantly to global climate change mitigation efforts and create a more sustainable built environment for future generations.

Works cited

1. What is Embodied Carbon? | US EPA, accessed December 15, 2024, https://www.epa.gov/greenerproducts/what-embodied-carbon
2. 1 - Embodied Carbon 101 - Carbon Leadership Forum, accessed December 15, 2024, https://carbonleadershipforum.org/embodied-carbon-101-v2/
3. Embodied Carbon - AIA California, accessed December 15, 2024, https://aiacalifornia.org/what-you-can-do-right-now/embodied-carbon-definitions-and-facts/
4. www.epa.gov, accessed December 15, 2024, https://www.epa.gov/greenerproducts/what-embodied-carbon#:~:text=Embodied%20carbon%20refers%20to%20the,a%20product%20and%20its%20disposal.)
5. What is Embodied Carbon? - CarbonCure, accessed December 15, 2024, https://www.carboncure.com/concrete-corner/what-is-embodied-carbon/
6. newbuildings.org, accessed December 15, 2024, https://newbuildings.org/code_policy/embodied-carbon/#:~:text=What%20is%20embodied%20carbon%3F,%2C%20and%20C1%2DC4).
7. Embodied Carbon - GSA Sustainable Facilities Tool, accessed December 15, 2024, https://sftool.gov/learn/about/658/embodied-carbon
8. Embodied Carbon in the Built Environment | Portland.gov, accessed December 15, 2024, https://www.portland.gov/bps/climate-action/embodied-carbon
9. cove.tools, accessed December 15, 2024, https://cove.tools/blog/green-building-what-is-embodied-carbon-impact-built-environment#:~:text=Impact%20on%20the%20Environment,-Embodied%20carbon%20has&text=Cradle%2Dto%2Dsite%20(A1,and%20the%20destruction%20of%20ecosystems.
10. Embodied Carbon 101: Building Materials - RMI, accessed December 15, 2024, https://rmi.org/embodied-carbon-101/
11. ROI: Designing for reduced embodied carbon - The American Institute of Architects, accessed December 15, 2024, https://www.aia.org/resource-center/roi-designing-reduced-embodied-carbon
12. Growing Impact: Urban embodied carbon | Institute of Energy and the Environment, accessed December 15, 2024, https://iee.psu.edu/news/podcast/growing-impact-urban-embodied-carbon
13. Why we must tackle embodied carbon to meet our climate goals | World Economic Forum, accessed December 15, 2024, https://www.weforum.org/stories/2024/01/tackling-embodied-carbon-in-housing-is-the-climate-solution-we-need-right-now/
14. rmi.org, accessed December 15, 2024, https://rmi.org/embodied-carbon-101/#:~:text=Designers%20can%20significantly%20reduce%20a,carbon%20and%20carbon%2Dstoring%20materials.
15. Reducing embodied carbon in new construction - McKinsey & Company, accessed December 15, 2024, https://www.mckinsey.com/industries/travel-logistics-and-infrastructure/how-we-help-clients/global-infrastructure-initiative/voices/reducing-embodied-carbon-in-new-construction
16. How To Reduce Embodied Carbon in Buildings and Why It Matters - RWDI, accessed December 15, 2024, https://rwdi.com/en_ca/insights/thought-leadership/how-reduce-embodied-carbon-buildings-why-matters/
17. Reducing Embodied Carbon in Building Systems: From Concept to Practice, accessed December 15, 2024, https://carbonleadershipforum.org/reducing-embodied-carbon-in-building-systems/
18. Embodied carbon: What it is and how to tackle it - RPS Group, accessed December 15, 2024, https://www.rpsgroup.com/services/environment/sustainability-and-climate-resilience/what-is-embodied-carbon/
19. Embodied Carbon: new regulations will drive the industry - Learn, accessed December 15, 2024, https://learn.aiacontracts.com/articles/embodied-carbon-new-regulations-will-drive-the-industry/
20. NBI Factsheet: Addressing Embodied Carbon in Building Codes, accessed December 15, 2024, https://newbuildings.org/wp-content/uploads/2023/03/NBI_Embodied-Carbon-Codes_Factsheet_v2.pdf
21. Embodied Carbon - New Buildings Institute, accessed December 15, 2024, https://newbuildings.org/code_policy/embodied-carbon/
22. Embodied Carbon Cities Policy Toolkit - RMI, accessed December 15, 2024, https://rmi.org/embodied-carbon-cities-policy-toolkit/
23. Embodied Carbon Initiative - RMI, accessed December 15, 2024, https://rmi.org/our-work/buildings/embodied-carbon-initiative/
24. Building Transparency: Homepage, accessed December 15, 2024, https://www.buildingtransparency.org/
25. Embodied Carbon in Buildings and Infrastructure | ACEEE, accessed December 15, 2024, https://www.aceee.org/embodied-carbon-buildings-and-infrastructure
26. Embodied Carbon - World Green Building Council, accessed December 15, 2024, https://worldgbc.org/advancing-net-zero/embodied-carbon/
27. Covering Embodied Carbon: why should I care? - Preoptima, accessed December 15, 2024, https://www.preoptima.com/the-carbon-source/covering-embodied-carbon-why-should-i-care