Embodied Carbon vs. Operational Carbon

Each week, we construct a city the size of Paris across the globe. Surprisingly, less than 1% of buildings have their carbon footprints assessed, and even fewer have a detailed analysis of the two different types of carbon: embodied and operational. Our shared goal in the Paris Agreement is to achieve global net-zero carbon emissions by 2050. To reach the lofty goals of the Paris Agreement, it’s vital to understand the differences between embodied carbon vs. operational carbon and their roles in climate change.

Embodied Carbon vs. Operational Carbon

The built environment is a major contributor to global climate change – it is responsible for about 40% of annual CO2 emissions. This carbon comes from two sources: embodied and operational. Most people are familiar with operational carbon – the carbon used in operating and using a building. This includes things like:

• Lighting

• Heating

• Ventilation

• Cooling, or air conditioning

• General power usage throughout the building

The operational carbon footprint of a building is the sum of all the carbon produced over the lifetime use of the building, which could easily be 50 or more years.

Embodied carbon is the carbon footprint of a building before it is built, and encompasses the greenhouse gasses emitted during the construction process. This includes things like:

• Extraction and production of materials

• Transportation of materials

• Manufacturing

• Construction

• Demolition and retrofitting

• End-of-life deconstruction

Embodied carbon is the “upfront carbon” that is generated before the building is used.

The 40% of annual CO2 emissions that come from the built environment are equal to 53 gigatons every year. To put that into perspective, just one gigaton is as heavy as 10,000 fully loaded U.S. Aircraft carriers. 13% of those emissions come from upfront, or embodied, carbon.

If only 13% of emissions from buildings come from embodied carbon, why do we focus on it? Because that carbon is being released into the atmosphere now, not over the next 50 or more years. If we can reduce embodied carbon now, we can have a significant impact on reducing the overall effects of climate change more quickly.

Additionally, our energy grid is getting cleaner. Over the last 50 years, the architecture, engineering and construction (AEC) industry has focused on making buildings more energy efficient. This means that buildings are using less energy overall, and the energy they are using is coming from cleaner sources.

Making buildings more energy efficient has lowered carbon operating emissions. But as operational carbon goes down, embodied carbon will account for a larger percentage of total carbon. By the year 2050, almost half of the carbon footprint in new construction will come from embodied carbon. Canada, Sweden, and Norway are already seeing an almost 50/50 embodied carbon vs. operating carbon split. This is because these countries have done a good job of reducing their use of fossil fuels and moved toward renewable energy sources. We need to start paying more attention to embodied carbon now if we want to make a difference in the future.

The True Cost of Embodied Carbon

As we decarbonize the grid, operational carbon emissions will gradually decrease. But since embodied carbon is spent before the building is used, it is a sunk cost and cannot be reduced after building completion. As we strive for net zero by 2050, embodied carbon will play a crucial role in whether or not we succeed.

Our carbon “budget” between now and 2050 is 420 GT (gigatons). That is the amount of carbon we can emit over the next 27 years, and still achieve the goals of The Paris Agreement. Right now, we are drastically overspending that budget: at the current rate of 53GT per year, we are on track to hit 1325 GT by 2050. To reduce this spending spree, we must tackle carbon that is emitted now – which is where embodied carbon comes into play.

The Urgent Need for Measurement and Reduction

Life-Cycle Assessment (LCA)

Life Cycle Assessment (LCA) is a way to understand the environmental impact of building something, like a house or a bridge, from start to finish. One Click LCA offers the tools you need to make this complicated process simple.

Here’s how it works:

Materials (Embodied Carbon): The first step is to look at all the materials needed for the construction. This includes things like wood, concrete, and steel. We track where these materials come from and how they are made, following the product from the forest or mine to delivery to the construction site.

Building (Embodied Carbon): Next, we examine how the construction process itself affects the environment. This involves looking at the energy used, the waste produced, and the emissions released during building.

Use (Operational Carbon): After the construction is complete, we consider how the building will be used. For example, in a commercial building, we might look at how the HVAC is set up to determine an estimate of life time energy usage.

End of Life: Finally, we think about what happens when the building is no longer used or needs to be replaced. Will it be demolished? Can parts of it be recycled or reused?

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