Embodied carbon is a central issue in sustainable construction. All construction materials and processes carry their own carbon footprint, making a building’s overall environmental impact far larger than its post-construction energy use.
Many efforts seek to reduce these emissions, but a recent study suggests adding carbon to construction resources — rather than taking it away — could help. The key lies in carbon capture and storage.
Conventional Approaches to Carbon Capture and Storage
Carbon capture technology comes in several forms, but all share a common goal. The aim is to contain CO2 emissions or remove the gas from the atmosphere and sequester it so it cannot leak into the environment.
At least 45 industrial facilities today are actively running carbon capture and storage projects. Roughly 700 more are in various stages of development. Many of these work by filtering waste gases from factory processes and compressing the CO2 into underground reserves. Others use the gases to power other workflows, like recovering oil from wells or fermenting crops to produce ethanol.
The benefits of carbon capture and storage are fairly straightforward. As large zero-carbon energy shifts take time to implement, carbon capture and storage stops CO2 from contributing to climate change in the meantime. However, conventional methods face a few drawbacks.
Building and running carbon capture technologies can be an energy-intensive process. Underground storage facilities can leak, and leaking CO2 can make nearby water undrinkable through heavy metal contamination. Injecting CO2 into oil wells is also dubious, as it can spread underground contaminants throughout the environment.
How Building Materials Could Improve Carbon Capture
A new study proposes an alternate carbon capture process. Instead of using CO2 for industrial power or putting it underground, organizations could store it within building materials. At an industry-wide scale, such a strategy could store over 16 billion metric tons of CO2, reducing the amount that enters the atmosphere each year.
Carbon storage on that scale would equal roughly 50% of all CO2 emissions the world produced in 2021. Naturally, achieving this level of sequestration is unlikely, but even a fraction of that amount could make a significant impact.
The primary promise of this method is that the world already needs and produces a substantial amount of construction materials. Consequently, using these resources as carbon sinks wouldn’t involve a significant increase in energy consumption. It would also reduce the impact of embodied carbon, as bricks and cement would counteract more emissions than they generate.
What Materials Are Best for Carbon Capture and Storage?
The benefits of carbon capture and storage through building materials vary depending on the material in question. Additional work is likely necessary to find the optimal path forward, but three types of resources have emerged as frontrunners.
Concrete
Concrete offers the most potential for carbon capture and storage projects. This is mostly because of the sheer volume of concrete world needs. It’s the world’s second most-consumed substance after water, so it provides a vast storage opportunity.
There are a few ways to sequester carbon into concrete. One is to add charred waste biomass into the mixture. Another is to capture carbon into artificial rocks to use as an aggregate, which is more complex but can hold larger amounts of CO2.
Previous research has found promising carbon offset alternatives in concrete, too. Hempcrete — which is made of hemp — absorbs more carbon than it releases, giving it a negative embodied carbon footprint.
Bio-Plastics
Making plastics from biomass instead of petroleum is another possible solution. This option is noteworthy because conventional plastics are infamously harmful to the environment but valuable as a construction resource. PVC can withstand UV exposure and resist moisture — helping it last a long time — so a sustainable version would have substantial lifetime benefits.
Bio-plastics could store more carbon by weight than any alternative. However, concrete still has the largest potential impact because of how much of it the world produces.
The most effective carbon capture and storage processes would combine these strategies. Concrete and plastics serve different purposes in construction, so a building could use both as a sequestration vehicle to maximize the sustainable benefits.
Biomass Fiber Bricks
Similarly to concrete, storing carbon in bricks would involve using biomass — this time in the form of natural fibers — to store CO2 as an additive within the conventional material makeup.
Studies have highlighted how alternative bricks can reduce embodied carbon. Using agro-forestry waste instead of conventional resources can reduce up to 1.5 million tons of CO2 annually. Using these bricks as carbon sinks could drive savings even higher.
Bricks may not be as common as concrete in modern Western construction, but they’re still common across the globe. Consequently, capitalizing on their potential in carbon capture and storage could produce impressive results.
Novel Materials Take Carbon Capture and Storage Further
Carbon capture and storage technology has struggled to prove its large-scale potential as an environmental technology. This new method of using building materials instead of conventional sequestration approaches could finally make it feasible. Even if a small fraction of the world’s construction resources switched to these alternatives, it could remove millions — if not billions — of tons of CO2.
