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.
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:
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.
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.
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.
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:
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.
Several sustainable building materials offer lower embodied carbon compared to conventional options. These include:
|
Material |
Source |
Benefits |
Applications |
|---|---|---|---|
|
Bamboo |
Rapidly renewable grass |
High strength, low embodied carbon |
Structural elements, flooring, cladding |
|
Hemp |
Plant-based material |
Excellent insulation, carbon sequestration |
Insulation, wall construction |
|
Straw |
Agricultural by-product |
Insulation, building material |
Insulation, wall construction |
|
Cork |
Bark of the cork oak tree |
Natural insulator, acoustic properties |
Insulation, flooring |
|
Wool |
Natural fiber |
Excellent insulation, low environmental impact |
Insulation |
|
Recycled steel |
Recycled content |
Reduced need for raw material extraction |
Structural elements |
|
Recycled glass |
Recycled content |
Reduced need for raw material extraction |
Insulation, countertops |
|
Low-carbon bricks |
Innovative production techniques |
Minimized carbon emissions |
Walls, facades |
|
Mass timber |
Engineered wood products |
Structural strength, carbon storage |
Structural elements, flooring |
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:
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.
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.
Mandating the measurement and reporting of embodied carbon in building projects is crucial for increasing transparency and driving reductions19.
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.
Numerous organizations and initiatives are dedicated to reducing embodied carbon in construction. These include:
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.
While this report provides a comprehensive overview of embodied carbon in building materials, further research and development are needed in several areas:
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.