The building industry contributes 11% of worldwide energy-related carbon emissions. One way to minimize this embodied carbon is through the use of eco-friendly construction materials.
For instance, grass-based wood alternatives like Plantd’s Oriented Strand Board do not require tree cutting and can reduce deforestation.
Other innovative options include carbon neutral concrete, steel and aluminum as well as low-carbon timber, stone and green roofs.
1. Carbon-Neutral Concrete
Concrete is used more than any other building material on earth, but it’s not without its environmental problems. The production of cement, a key ingredient of concrete, is responsible for about 8% of global carbon emissions. Researchers are finding ways to make this process more environmentally friendly.
For example, engineers at Washington State University have infused concrete with microalgae to create carbon-neutral or even carbon-negative concrete. As Popular Mechanics explains, the microalgae replace limestone (a common ingredient in concrete) that would otherwise be mined from the earth with a type of calcium carbonate grown through photosynthesis. The concrete absorbs more carbon dioxide than it emits during the manufacturing process.
Another way to reduce the environmental impact of concrete is to add in biochar, a type of charcoal made from waste biomass like agricultural and forestry byproducts. This is also known as “renewable aggregate,” and it can be added to the mix to improve the concrete’s strength. The concrete manufacturer Cemex launched a version of this product called Vertua Ultra zero in France and the UK earlier this year. The embodied carbon reduction for this product is about 70% lower than conventional concretes.
2. Carbon-Neutral Cement
Concrete, the world’s most widely used construction material, is a significant contributor to global carbon emissions. To curb its embodied energy, researchers are working to make it carbon neutral or even carbon negative.
One approach involves replacing part of the cement with a type that is made from captured industrial emissions and carbon-absorbing olivine. London-based start-up Seratech has developed a concrete mix that achieves this.
Another approach focuses on the kilns used to heat the limestone during cement production. This can be replaced by a renewable biomass fuel or, as in the case of a planned plant upgrade in Sweden, with green hydrogen produced by renewables.
And, perhaps most exciting of all, UC Boulder researchers have developed algae-grown limestone that could be used in concrete to make it carbon negative. If all the traditional ground limestone that is typically added to concrete was replaced with the algae version, it would remove two gigatonnes of CO2 from the atmosphere annually. The resulting concrete would then act as a permanent storage of carbon. It is the only building material known to do this.
3. Carbon-Neutral Steel
The production of cement, concrete’s key ingredient, accounts for 8% of the world’s carbon emissions. However, it isn’t possible to stop using concrete to build structures, and researchers are looking for ways to make it carbon negative.
One way is to add a biogenic limestone that pulls carbon from the air into the concrete mix. Another is to use magnesium-based concrete, which can absorb CO2 instead of emitting it into the atmosphere.
Steel is another critical building material, and companies are working to produce carbon-neutral steel. Several processes decrease the carbon footprint of steel by decreasing energy usage during the smelting process, and by using renewable power to run the electric arc furnace (EAF).
Wood is also becoming a more popular alternative to steel in construction, but it is challenging to find low-carbon wood products. However, innovations like lamination and prefabrication are lowering the embodied carbon in timber framing. Plus, compared to shipping heavy materials like steel to a build site, wood is lighter and reduces transportation costs.
4. Carbon-Neutral Wood
A range of building materials can be used to build structures and help reduce a structure’s carbon footprint. However, many are often sourced from fossil fuels and therefore have high embodied emissions, which must be offset by carbon-neutral or low-carbon activities in order to meet climate goals.
A growing number of developers and manufacturers are focusing on replacing concrete and steel with wood, using a method called mass timber. Developed by Spiritos Properties as part of the RMI-led Advanced Building Construction Collaborative, mass timber is created by laminating stranded, fast-growing materials from sustainably managed forests together to create strong beams and structural components for tall buildings.
The carbon benefits of using timber are clear: It has a lower carbon footprint than concrete and steel, and locks up a significant amount of stored carbon for decades or even centuries, depending on the management and harvesting regime. This carbon sequestration can offset the energy and emissions associated with processing the material, as well as those generated by its burning.
Its potential to reduce a building’s embodied emissions is also a key reason why governments across the globe are investing in ecological forest management approaches, which can increase the amount of stored carbon in harvested wood products and help meet climate goals. Yet there are challenges to this, too.
5. Carbon-Neutral Metals
As we move towards carbon neutrality, new innovations in construction materials could be the key to reducing embodied emissions. Some of these innovative technologies, such as carbon-negative wood, are already being used in buildings around the world. The technology reduces embodied carbon by sequestering more carbon than it releases during production and usage.
The carbon-negative timber construction material is harvested from forests that absorb carbon through photosynthesis. This is a great way to offset the heavy reliance on fossil fuels used in the production of concrete and steel, but it’s important that these forests are being managed sustainably.
Companies like Mighty Buildings are collaborating with materials technology firms to make carbon-negative timber a viable building solution. In addition to being environmentally friendly, the material is termite-resistant and moisture-resistant, allowing it to be used in various applications such as walls, floors, roofs and interiors.
In addition to wood, carbon-negative cement is another carbon-neutral building material that can be made using captured industrial emissions. The process is called direct air capture (DAC), and it can be used to replace traditional cement. It’s also possible to use olivine sand instead of limestone in concrete, which can lower the carbon footprint even further.