Can Buildings Be Carbon Sinks?
As last month we introduced you to the general theme of our upcoming event “The Green Real Estate”: Beyond Net Zero, we will during this month focus on the topics we will address during our event. The first one being carbon sinks in the building sector, this article will provide you with all the keys to understand the carbon sink concept and related solutions.
Carbon sinks: a way to achieve carbon neutrality
On Earth, the main carbon sinks are the soil, forests, and ocean; in fact, they are absorbing more carbon than they emit, and can mass store carbon emissions.
In order to achieve Earth carbon neutrality they are essential, but this was without considering added anthropogenic carbon emissions and resulting global warming. Natural carbon sinks are being used above their capacity and the carbon they store, such as in forests, is released into the atmosphere through forest fires, land use changes or logging. Therefore, for us to achieve carbon neutrality, we must put in place drastic carbon emissions reduction techniques before these emissions are emitted and we need to compensate for them.
As one one of the largest CO2 emitting sectors, we must rethink the building industry to not only be designed, built and operated low carbon but to act as a carbon storage mechanism
Reducing building carbon emissions through material selection and new technologies
From the material selection to the use of new technologies, carbon sinks are much needed solutions for a greener future in the building sector. To rethink buildings, it’s important to know that buildings could become carbon sinks if they were mostly made from wood instead of cement and steel.
Indeed, the most effective solution is the use of bio-based materials such as wood and bamboo. Bio based materials remove carbon from air by sequestering it and transforming it via photosynthesis. This means they absorb more carbon than they emit, essentially being carbon negative and lead the building towards carbon neutrality. Bamboo is a very popular solution in both tropical and subtropical climates, which can be used for flooring as much as for building structure. Timber is also a solution often associated with green building which can be used for walls construction, building structure, and mostly flooring and covering.
Using the building's vertical structure by covering it with vegetation allows to maximize absorption of CO2 in a building without sacrificing space, especially in a city. These walls are made of vertical panels with an irrigation system and 1 m² of them can absorb up to 2kg of CO2 per year. This green facade can also be used indoor and outdoor to improve air quality and can also act like insulation to reduce heat gain and loss.
Concrete produces 8% of global carbon emissions. Concrete is a mix of cement, construction aggregate, water, and chemicals. There are two concepts to create green concrete :
The first one is to use recycled concrete content or fly ash as part of a circular design concept. In fact, concrete can be recycled by grinding it up, separating fine and coarse materials and magneted to remove steel. Fly ash can also replace cement in the concrete mix. Made of aluminous and siliceous material forming cement to the addition of water, fly ash improves concrete strength and durability. This way, both techniques reduce our reliance on new materials and the overall embodied carbon of concrete.
The second one is to incorporate new technologies to capture and store the carbon in the concrete, such as algae or hempcrete. Concrete with algaes bricks can be created by growing algae in a mixture of sand, seawater and cyanobacteria. Raw algae can also be mixed with more conventional concrete, storing carbon and making the concrete carbon neutral. In the same way, hempcrete concrete has a high fire resistance, an excellent moisture and abrasion resistance, a good carbon storage capacity and it’s non-toxic.
Using the same process as green walls, green roof sequesters carbon in plants and substrates. As green walls, they also allow saving space in cities where there is not for parks and gardens, which has a significant impact on the capture and storage of air pollutants on a building scale.
To learn more: Join Our Event "The Green Real Estate: Beyond Net Zero" on February 9th 2023!