While progress has been made in decarbonizing the energy sector, industrial process emissions remain a challenge. Embodied carbon in buildings, particularly in their materials, is a significant source of emissions. Cement production, for example, accounts for a substantial portion of global greenhouse gas emissions. Decarbonization of materials requires innovative approaches, including biology-inspired design and utilizing carbon already present in the biosphere. When considering how to reduce greenhouse gas emissions, addressing this blind spot is crucial for achieving sustainability.
When we think about the drivers of climate change we often think about the greenhouse gas emissions caused by energy generation. And rightly so; the coal and natural gas we burn to meet our demand for electricity around the world are currently substantial global contributors to greenhouse gasses.
Meanwhile, solar and wind powered renewable energy generation are now a cost competitive source of new energy for 2/3 of all humans on the planet.
And battery storage is on the cusp of being cost competitive for meeting peak load demand.
So, in many ways, decarbonizing our energy sector can be seen as technologically and economically solved.
What is missing is the political will to roll out this change.
What decarbonizing our energy leaves behind in terms of emissions is one transportation (which is fast electrifying), and two the third of global annual emissions known as “Direct Emissions,” which includes “industrial process emissions.” These are emissions caused by the core chemistry of making materials like cement, steel, and petrochemicals like plastic, and they are very hard to decarbonize.
To illustrate, in the field of architecture there is a distinction between the embodied carbon and operational carbon of a building. In a typical building three quarters of emissions come from operations and the remaining quarter comes from processing the materials that will go into the new construction.
But for buildings built with sustainability in mind we have gotten so good at minimizing operational carbon emissions — emissions associated with heating, cooling, and turning the lights on — that the biggest source of climate impact in these new buildings is the emissions associated with the materials of the building itself — the building’s embodied carbon.
We can decarbonize operations, embodied carbon is the next challenge.
But how, and why are materials such emitters?
Let’s look at cement.
Concrete, which is cement plus aggregate (rocks, gravel, sand), is the second most consumed material on earth after water. And a third of the building stock that will exist in two decades has not been built yet.
The production of cement represents at least 8% of current greenhouse gas emissions globally. More than half of those emissions are caused by the core chemistry of making cement – regardless of what fuel is used to contribute heat to the reaction.
The heart of cement production is taking limestone (CaCO3) and heating it up to kick out a CO2. Limestone is formed by the fossilization of marine organisms like shells and corals. So just like fossil fuels are fossilized ancient organisms who busily captured carbon for hundreds of millions of years, limestone, the key ingredient in cement, can be seen as fossilized life. How do we decarbonize that?
Focusing so narrowly on energy has left us with a collective blind spot to the third of global emissions that come from the intrinsic chemistry of stuff. Decarbonizing materials is an important frontier of innovation for decarbonizing our society.
One thread of research in this domain is biology inspired and empowered design. Once we recognize these materials are connected to ancient life, maybe then we can reinvent them with the help of organisms and ecosystems living today and build with the carbon already in the biosphere instead of pumping it out of the ground.