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Why Real Estate’s Embodied Carbon Levels Are Impossible to Calculate

With this year’s United Nations Climate Summit drawing to a close last week, the spotlight of concern seems to have been cast on the construction industry. Now that development activity for new buildings has rebounded to pre-pandemic levels in most places, so have carbon emissions. The sobering reality of this year’s summit was the fact that as of right now, the real estate industry is nowhere near on track to fully decarbonize by 2050.

Buildings haven’t traditionally been at the forefront of international climate conversation (the fossil fuel and transportation industries have usually taken center-stage), but that has been changing in recent years. We’re all well aware by now that real estate is responsible for almost 40 percent of global greenhouse gas emissions, 28 percent of which comes from operational emissions. But a lot of the focus of COP27 was on the remaining 11 percent that comes from the act of building new real estate, or as we know it, embodied carbon

If you need a quick refresher, embodied carbon refers to the greenhouse gas emissions that are produced during the processes of construction material production, shipping, installation, upkeep, and disposal. Many believe that reducing those embodied carbon emissions will lead to a more sustainable property industry. The U.S. Green Building Council’s LEED Certification offers Materials and Resources credits of up to 5 points for demonstrably reducing embodied carbon emissions, but accurately showcasing the before-and-after levels of embodied carbon is a huge problem in and of itself.

When it comes to accurately determining embodied carbon levels, you’d likely have an easier time navigating the Marianas Trench with just a pool noodle. Embodied carbon cannot be readily quantified, because it’s not like you can crack open a slab of concrete or split a steel beam and count the carbon particles within them. Even if you did, you’d get a woefully low estimate compared to the material’s actual lifetime carbon footprint.

Calculating embodied carbon levels is an arduous task that requires some serious deduction using information of where the material came from and the methods used to produce it. A material’s embodied carbon includes all of the carbon it took to extract it, process it, and deliver it to the construction site. That’s why two materials that have the same appearance, cost, and performance standards can have very different embodied carbon properties. For instance, a fully recycled steel beam made in a facility powered by renewable energy can look exactly like a virgin steel beam made with a coal-fired furnace, but the two contain quite different amounts of embodied carbon.

Construction materials are known to be the main culprits of embodied carbon. Concrete in particular is one of the worst offenders as its emissions clock in at 8 percent of the global share, which is neck-and-neck with steel production, but the impact that materials have on the climate crisis is larger than the amount of carbon they wheeze. The most recent UN Global Status Report for Buildings and Construction shows that 100 billion tons of waste is caused by construction, renovation, and demolition, and 35 percent of that waste gets stuffed into landfills. But while the UN has a lot of hard statistics to present, the true amount of embodied carbon that exists is a number so elusive that even an international coalition made up of 195 countries and their respective governments can’t come up with an answer. 

“We truly have no idea where we are with embodied carbon levels,” was the key phrase from Fiona Cousins, Principal of the New York office of the multinational services firm Arup (and member of the advisory board for Local Law 97), when I spoke with her for this article. “Developers embarking on new projects want to know how the decisions they make at the concept stage are going to impact the rest of the project, because that’s where the biggest point of leverage is,” she said. “But the problem is that the data about embodied is very general, so developers actually have less information about the projected carbon impact at square one than they otherwise would farther along in the project.”

In theory, the most important time to calculate embodied carbon levels is right at the design stage, but developers looking to deliver low-or-zero carbon buildings are faced with a conundrum from the get-go. Cousins explained that developers have a choice to make a building out of concrete or steel. Again, both of these materials are equally energy and carbon-intensive, but they’re both necessary to get a building off the ground. There’s no obvious choice between the two, and the data quality doesn’t make the decision any clearer. “These are the big bad materials when it comes to carbon output, but even if you know on average what those figures are, you can’t get to the details,” she said. “What you get is factory gate figures, which then doesn’t tell you the amount of energy used on-site to extract these materials nor do they tell you whether the piece of material was brought by plane, truck, rail to where it is.”

Any construction material’s embodied carbon cannot be determined from the completed product alone, the manufacturer must do an assessment and be transparent about the manufacturing process. But since materials go through an incredibly complex production supply system, that transparency is easier said than done. The problem is also made worse by a definitional overlap. The operational carbon of the iron mine, steel mill, and automobile factory that resulted in the creation of your car may be regarded as the embodied carbon of those facilities at one time.

How to accurately pinpoint the levels of a product’s embedded carbon is a relatively recent area of study, and there are no accepted quantitative guidelines. But thanks to the new attention drawn to embodied carbon on an international scale, that’s beginning to change. A considerable amount of work to standardize CO2 measurement procedures is underway, both from public and private entities. Denmark, Finland, France, the Netherlands, and Sweden have enacted legislation to standardize and regulate whole-life carbon emissions from buildings. For reference, whole-life carbon emissions refer to the carbon emissions brought on by the full lifecycle of a building, from material extraction, construction, operational use, demolition, and disposal. 

Since embodied carbon is considered a subset of whole-life carbon, its impact is taken under consideration. Arup also recently released their international dataset for whole-life carbon emissions with the goal of extracting more accurate guidelines for determining embodied carbon levels (the firm is also currently developing a whole-life approach for infrastructure projects). The pieces of legislation and emerging datasets are certainly a starting point for unveiling an accurate assessment of embodied carbon levels, but the sad fact is that we’re lost in the dark when it comes to our ability to calculate embodied carbon levels. As Cousins puts it, “we’ve done the very best we can with the data that is available to us, but the data is not really available.”

There’s an inconvenient truth when it comes to real estate’s sustainability: the most eco-friendly buildings are the ones that have already been built. But population growth, a global housing shortage, and the rapid pace of urbanization has created a need for more infrastructure—so the existing building stock isn’t enough to sustain us all. As new buildings are developed and constructed, especially in well-developed economies, their carbon footprints will be scrutinized. But in order to do that, we will need to understand the carbon output of the materials we’re working with, and we can’t possibly commit to lowering carbon levels if we can’t accurately measure them in the first place.

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