Why focus on embodied emissions?
When I surveyed the landscape of Embodied, Operational, and End-of-Life emissions in the built environment last fall, it was clear that Operational was the cool kid at the party. In the United States there has been a growing interest over the past year to Electrify Everything, which– from a buildings perspective– primarily relates to reducing our operational emissions. From deploying renewable energy and storage in buildings, to retrofitting with more energy efficient products, to better managing energy demand response, there has been SO much exciting traction in the area. Don’t get me wrong, there is still much more work to do. But attention has entered the desired flight path.
This got me thinking… where in the built world is attention still lacking? My conclusion: Upfront embodied emissions (e.g. cement and steel manufacture) and End-of-Life emissions (e.g. refrigerant leakage, waste management). If we can bring attention to these sectors, we’ll have greater opportunity to meet our climate change goals.
But first, some definitions. The World Green Building Council defines these terms as follows:
Embodied – Emissions associated with materials and construction processes throughout the whole lifecycle of a building or infrastructure, such as material extraction, transport to manufacturer, manufacturing, transport to site, construction, etc.
Upfront – The emissions caused in the materials production and construction phases of the lifecycle before the building or infrastructure begins to be used. These emissions have already been released into the atmosphere before the building is occupied or the infrastructure begins operation.
End-of-life – Emissions associated with deconstruction/demolition, transport from site, waste, processing and disposal phases of a building or infrastructure’s lifecycle which occur after its use.
So why focus on upfront embodied emissions first? If my goal is to spark a new wave of attention, the reality is that embodied emissions are more comprehensible. We create materials and move them around. They are convex rather than concave. Contrast this with end-of-life emissions, which our society–myself included– approaches with an “out of sight, out of mind” mentality. It’s a much harder story to tell.
Upfront embodied emissions in the built world are also a tremendous contributor in their own right– 11% of global CO2. This places it, in the popular game of “If This Sector Was A Country,” squarely between the United States (15%) and India (7%). And the sector is growing; global building stock (i.e. demand for construction materials) is on track to double its footprint by 2060.
Why focus on concrete / cement?
What makes concrete and cement an important (and fun! sexy?) problem to solve?
Concrete–and by extension, cement–is all around us. It supports the buildings we live and work in. It structures the facilities we depend on, from the plants that treat our wastewater to the bridges that connect us. Concrete is surprisingly simple. Just mix water, aggregate (e.g. gravel, sand), and a binder (here’s where cement comes in) and voila: strength impenetrable.
Concrete is popular, a global star. That dependable friend everyone relies on (yet too often takes for granted). Concrete is timefull and timeless. It is ancient, contemporary, futuristic. Its impact will only continue to grow as we continue to build and repair more buildings and infrastructure around the world. And yet it is forgettable.
At 6% global carbon emissions, cement is worth our attention. (For context, aviation contributes 2.5% global CO2 emissions.) Cement is the lifesource of concrete, one of its key binding ingredients. The most popular type of cement, known as “Ordinary Portland Cement,” is also the most stealthy. To produce OPC, limestone (CaCO3) with heat results in lime (CaO) and carbon dioxide (CO2). This direct carbon emission packs a punch. Pair that with the indirect emissions of industrial heat and you can quickly see why cement is such a big carbon emitter.
We have many shots on goal. What’s so exciting is that rethinking cement and concrete affords us many pathways to reduce and even remove CO2. We don’t need to reduce our use of concrete / cement. We just need to rethink our recipes.
Use recycled concrete
Sequester CO2 into aggregate
Alternative recipes to OPC
Recycle for aggregate
Sequester CO2 into mix
Excitingly, attention IS already starting to grow. Earlier this year, Bill Gates addressed our favorite binder head on as one of his key questions to ask about any climate change solution: “So what’s your plan for cement?” And today, Earth Day, the Biden Administration specifically called out their goal of “expanding carbon capture and green hydrogen to forge cleaner steel and cement” and acknowledged that “the government can use its procurement power to support early markets for these very low- and zero-carbon industrial goods.” (That’s a big deal, since the public sector purchases half of the cement produced in the United States.)
But we need more to join, especially to address the surrounding soft infrastructure. Addressing emissions from cement will take new research and development. It will take new policies and government procurement mandates. But it will also take soft infrastructure to really seal the deal– to address hidden frictions that slow the rate of acceptance and deployment. We saw this with the initial rollout of the COVID vaccine in the United States. At the start, much of the soft infrastructure was missing. This led to slower deployment times, and greater hesitancy among the public. I’m not discounting the benefits of learning through trial and error here. All successful projects start this way. But if we project this along the timeline for climate change, we just don’t have that long to figure it out. What other means can we use to stir more hearts and minds towards decarbonizing our cement industry? What other frictions can we predict and get started on, now?
Art by Juan Marin from Unsplash