Buildings as a carbon sink
How our buildings can save our planet instead of destroying it
Hi, I am Aleksei Kondratenko, PhD Researcher at Politecnico di Milano, and AI Intern at DBF. I am writing a series of blogs exploring how supercomputing and machine learning can be used to address the carbon impacts of the building industry. In the second post, we explore the concept of a carbon sink and how it becomes a powerful idea for building design.
Why do we need carbon sinks?
Reducing greenhouse gas emissions is not enough to prevent a catastrophic rise in global temperatures. Once they are emitted, we are stuck with harmful greenhouse gasses for a long time. Nitrous oxide (N2O) sticks around for more than a hundred years. Even worse, Carbon Dioxide (CO2) emissions can remain in our atmosphere for thousands of years. So, even if we completely stop carbon emissions today, the Earth’s temperature will continue to increase for a lot of years.
So in addition to reducing emissions, we also need to find ways to remove (sequester) excessive greenhouse gasses from the atmosphere. Fortunately for us, Mother Nature has already created CO2-capturing machines. Trees, soil, and the ocean naturally sequester CO2 and are examples of “carbon sinks”. However, to balance the impacts of human activity, such as buildings, cars, farms, and factories, more needs to be done.
As a quick reminder, anything that removes more carbon from the atmosphere than adds is known as a “carbon sink”, while anything that produces more carbon into the atmosphere than takes out of it is known as a “carbon source”.
In my last post, “buildings as a carbon source” we saw how buildings are a major source of carbon emissions, and how this harms the planet. Now, let’s imagine what would happen if buildings performed as carbon sinks, and what this means for the planet.
Buildings as a carbon sink for operational carbon
Operational carbon emissions happen once a building has been constructed, it starts to operate, and the people are living in it. To imagine how buildings can be a carbon sink for operational carbon, we need to rethink building energy consumption and building energy sources.
Building energy sources are the responsibility of the energy sector and its ability to develop, promote, and implement renewable energy sources (mainly wind, solar, hydro, and nuclear). Additional solutions like electrified heat pumps can be considered a viable alternative to gas for heating. In short — the idea would be to electrify all building operations and use renewable energy sources. While this idea sounds straightforward, its implementation will take time. Presently less than 20% of all energy sources used in the world are renewable and historically it takes at least several decades for humanity to switch to a new source of energy.
Building energy consumption is being reimagined by many architects, owners, and engineers through initiatives like passive design (design for as minimum operational carbon as possible), and energy demand management (smart buildings). Another option is to generate renewable energy onsite (such as PV panels on the roof) to offset the building’s operational carbon. One fascinating example of it is Powerhouse Brattørkaia in Trondheim, Norway. It has so many solar panels on its particularly-shaped roof, so it is able not only to power itself but also to produce electricity for the district nearby. This example is quite particular though!
It is already possible for our buildings to act as a carbon sink for operational carbon and many tools are available to us: renewable energy sources, passive design, careful real-time management, and even on-site energy production. But please do not forget that during the materials’ production, construction, and maintenance of PV panels, wind turbines, and other structures for renewable energy generation a lot of embodied carbon is emitted, and they firstly must offset it during their operation to even justify their use from the perspective of a carbon sink.
Buildings as a carbon sink for embodied carbon
Embodied carbon relates to all other stages of a building’s life cycle such as the production of materials needed for the structural system, building services, finishings, facades, their transportation to the site, construction, maintenance/repair, demolition, and waste disposal. To imagine how buildings can be a carbon sink for embodied carbon, we need to firstly rethink building structural materials since the structural system is the biggest contributor to the embodied carbon.
The production of building structural materials like steel and concrete creates a lot of harmful CO2 emissions. Despite best efforts by industry to mitigate their respective impacts, for now, it is hard to imagine how steel and concrete buildings could ever be carbon sinks. However, there is a solution to the carbon sink question in the form of a very old structural material — wood (or timber). Timber, and in particular, engineering products made of it(mass timber) are gaining popularity as an alternative to steel and concrete. This comes with good reason; as a tree grows, it takes CO2 from the environment and releases oxygen into it. Ideally, CO2 can be stored in a tree for a long time, however, events such as bushfires, rotting, falling branches and needles, and other factors, will release it back into the atmosphere. This may sound benign, nevertheless, this is a critical issue. Did you know Canadian forests produced more carbon than removed since 2001 (i.e., behaving as a carbon source)?
Mass timber buildings can serve as carbon storage and prevent this CO2 release back into the atmosphere for a long time. According to a recent study, 1 cubic meter of mass timber can store up to 1 ton of CO2, and a building constructed from mass timber stores more carbon per square meter than the equivalent area of a living forest. Furthermore, the study concludes that mass timber building can sequester more CO2 than the embodied carbon emitted during its production and manufacturing — that’s right, building as a carbon sink.
During the production stage, the embodied carbon of mass timber structures is less than steel and concrete ones. In addition to just looking good, timber buildings also have the advantage of being much lighter and faster to construct (thanks to prefabrication). Current mass timber products allow the predictable and controllable fire design and are generally more fire resistant than typical steel structures. It leads to softening of building regulations towards mass timber buildings, and its increased use all over the world (even in mass timber skyscrapers).
Unfortunately, conservative public perception (it is always faster and easier to improve the technology than eliminate common human stereotypes and prejudices), lack of expertise, and highly volatile (especially in the last years) prices still leave mass timber buildings far behind its concrete and steel counterparts in terms of use.
Speaking about the benefits of buildings made of timber we must be careful to note a couple of things. For the building to be a carbon sink a mass timber material must be taken from a sustainably managed forest where for each cut tree several new ones are planted. Otherwise, extensive use of mass timber buildings could lead to irresponsible use of natural resources and consequently huge deforestation. In addition, the CO2 taken from the atmosphere by trees planted instead of ones used in mass timber buildings could be also treated as stored CO2 and subtracted from the total life-cycle embodied carbon of the mass timber structure (although there are arguments about how exactly should we considered stored carbon in mass timber buildings). The second thing is an end-of-life scenario. If structural components of mass timber buildings are incarcerated or sent to a landfill after its end-of-life, the stored CO2 could go back into the atmosphere. Consequently, the best-case scenario from a carbon sink perspective will be to reuse at least a part of building stock in future buildings and consider this potential reuse in the design stage (design building in a way that it could be easily demountable after its end-of-life).
Conclusion
From this article, you learned what a carbon sink is, why it is important, and how our buildings can serve as carbon sinks. I have to note that everything written in this post unfortunately is not applied to every new building in the world. Moreover, it is applied just to a small percentage of them due to the lack of expertise, access to the required technologies, and the relatively high price of the discussed solutions. Researchers and practitioners around the world are working hard every day to make these concepts more accessible and widespread. Reaching this final point of the article, you are hopefully convinced that to turn our buildings from carbon sources to carbon sinks would be an amazing thing to do, but I rather say it would be a tragedy not to do it.
Which technologies can be used to help us to turn our buildings into carbon sinks? To find out, stay tuned for part 3!
About the Author
Aleksei Kondratenko is an AI Design Intern at Digital Blue Foam and PhD candidate at Politecnico di Milano. With a background in structural engineering, he aims to improve the sustainability of the built environment through the most modern digital technologies. He currently works on AI and ML applications in structural engineering presenting his work at prestigious global conferences like AI in AEC and DigitalFutures.
About DBF
Digital Blue Foam (DBF) comprises an elite mix of designers and technologists from around the world who share a strong commitment to empowering a revolution in architecture, engineering, and construction (AEC) industries toward carbon-negative projects by leveraging data-driven, AI-powered, collaborative, and sustainable approaches. We embrace collaboration and sponsorship, and we thrive at offering customized solutions that make designing a hassle-free and intuitive process. To learn more about Digital Blue Foam, visit our website.
