Climate Cost of Our Buildings: How to Lower Embodied Carbon?

Carbon emissions significantly contribute to climate change, with the built environment accounting for roughly 40% of global annual carbon emissions. This alarming statistic has prompted industry organizations and companies worldwide to establish ambitious carbon reduction and net-zero targets. A critical element in achieving these goals, and a substantial source of emissions within buildings, is embodied carbon.

Embodied Carbon

Embodied carbon includes all carbon emissions associated with building materials and includes all phases of the material lifecycle. For exploration, emissions produced from raw materials start with the extraction of raw materials from the earth and carry through production, transportation, on-site construction, and then end-of-life with either disposal or recycling.

Embodied Carbon in Key Phases of Building Material Life Cycle

Embodied Carbon Footprint

Embodied carbon emissions will occur in every phase of the building material life cycle:

Raw Material Extraction

This phase will include mining or harvesting a raw resource like limestone for cement, sand for glass, or timber for wood products. This can even include “natural” mineral extraction like granite and soapstone for countertops., even harvesting post-consumer wood products (reclaimed). This phase is usually done with heavy machinery or earth movers that run on fossil fuels, and if they are logging, they may be clearing vegetation or assuming land is degraded.

Manufacturing and Processing

Raw materials are processed and manufactured into useful building products like cement, steel, bricks, and building insulation. Usually, there are high energy inputs in industrial processes with commonly coal or natural gas burned to produce energy that led to carbon dioxide emissions.

Transportation

Once materials produced, building materials are transported to construction sites, using trucks, ships, and trains, effective adding carbon footprint.

Construction Activities

The actual process of assembling a building includes machinery and tools that consume fuel and electricity. Construction waste generated on site also adds to the overall impact.

Maintenance and Renovation

During a building’s life, periodic repairs or upgrades may require new materials. These introduce additional embodied carbon even after the building is completed.

End-of-Life

When the building is demolished or dismantled, the disposal of its materials also contributes to carbon emissions. Even recycling involves energy use, though it is generally less than creating new materials.

Which Materials Have the Highest Embodied Carbon

Some materials used in construction are far more carbon-intensive than others. Because of their strength, durability, and availability, these materials are among the few that are in common use, but they come with serious environmental costs. Here are some examples:

• Cement, the main ingredient of concrete, is one of the top single contributors to industrial carbon dioxide emissions. Production of cement entails a chemical reaction that releases a large quantity of CO₂.
• Steel is produced in high-temperature furnaces powered by the combustion of fossil fuels, which thus makes it a material of the highest embodied carbon.
• Bauxite requires a huge amount of electricity for refining into aluminum, with electricity coming chiefly from coal or gas.
• Glass manufacturing processes demand heat and energy, magnifying the embodied carbon footprint. Making glass also consumes energy at high temperatures, working towards increasing its embodied carbon footprint.
• Insulation cuts down operational energy consumption; however, some foam-based type embodies high emissions since it is petroleum-based in their production process.

Developing an understanding of what materials contribute more to embodied carbon will allow architects and builders to better choose products for their projects.

Materials with High Embodied Carbon

Global and Local Impact of Embodied Carbon

We estimate that embodied carbon contributes to approximately 11 per cent of total anthropogenic greenhouse gas emissions. A seemingly small piece of the pie, however, looks very different when we focus on just the construction and building sector. That number suddenly feels a lot more critical and is only anticipated to grow. Here is why these matters:

• Urbanization is skyrocketing, especially in developing countries. With urbanization comes more housing, more roads, and more infrastructure.
• The materials we are making, concrete, steel, and brick, all of them take carbon to produce, and we are using huge quantities of them.
• It is difficult to conceptualize, but effectively, we are building a fresh New York City every month for thirty years.

Conclusion

Embodied carbon is a significant, yet often underestimated, component of the built environment’s climate impact. From extraction to end-of-life, every stage of a material’s journey contributes to this embedded carbon footprint. Recognizing the materials with the highest embodied carbon and understanding the global implications of our current construction practices are crucial first steps. The good news is that by shedding light on this issue, we can begin to explore practical solutions for designing and building more sustainably. In our next blog post, we will delve into actionable strategies for significantly lowering embodied carbon in our buildings.