During the 10th annual World Green Building Week, the World Green Building Council issued an ambitious new vision for the construction industry. The aim is to reduce embodied carbon emissions (ECE) by 2030 and achieve 100% net zero emissions by 2050. This comes in when a recent report shows that building and construction are together responsible for 39% of global carbon emissions. Out of which, operational emissions account for 28% and ECE accounts for the remaining 11%.
Focusing on the ECE, the material used in the construction process throughout a building’s lifecycle plays a crucial role. For example, use of smog-engulfing concrete improves air quality instead of emitting carbon. The material greatly helps buildings to reduce smog.
The manufacture of conventional concrete and its transportation, construction and lifecycle are together accountable for ECE. Although these emissions have been overlooked in the past, the Intergovernmental Panel On Climate Change (IPCC) conducted milestone research on it. As a result, IPCC confirmed that it is critical to cut down ECE to keep the global temperature below 1.5℃.
While on the other side, it is foreseen that new construction will double the world’s building stock by 2060. Eventually, it will result in higher carbon emissions. Therefore, the new report is calling to act on changing how buildings are designed, constructed, used and reduced.
Lately, new living concrete material is making headlines – as a promising sustainable construction material for smart cities. With the kind of composition it has, it seems that its production and use in buildings will address the ECE challenge. Living concrete will be unlike the production of conventional concrete that contributes 2.8 gigatons of emissions annually.
Embodied Carbon Emissions’ New Enemy
A team of researchers at the University of Colorado, Boulder have created an innovative sustainable concrete. The material is alive and can even reproduce and trap carbon. So, the point of fact, it is anticipated to be a promising material for the construction industry.
The new material has been developed with the help of cyanobacteria – a common class of bacteria that captures energy via photosynthesis. The material originates from the bacteria, acts as a favourable habitat for them to reproduce later on. This is opposed to the regular concrete which is unfavourable for bacteria.
The colour of the material is green due to cyanobacteria which are responsible for a harmful algal bloom and is also green in colour. As stated by Dr Wil Srubar, a structural engineer and head of the research project, “It really does look like a Frankenstein material.” But the green colour disappears as the material dries, reported by the New York Times.
Birth Of Living Buildings
Furthermore, according to the research team, this innovation will lead the way for living buildings in the future. The magic here is that one day, these buildings would be able to heal their own cracks just as human skin and purify the air.
As per the authors in the study published by Advanced Science News, microorganisms can be utilised for various purposes in the building. They can be leveraged as living building materials which can reduce the time required for manufacturing. Additionally, they can provide an increased mechanical benefit while sustaining biological function.
This particular project was funded by DARPA, the research arm of the Department of Defence, US. DARPA was seeking a quick process that could create a living concrete. Further, Dr Srubar added that “This is a material platform that sets the stage for brand new exciting materials that can be engineered to interact and respond to their environments.” He continued saying that “This was just the beginning and the sky is the limit”.
The Succesful Experiment
Towards their first successful attempt, the researchers experimented by putting colonies of cyanobacteria in a mixture of warm water, sand and nutrients. Soon the bacteria started absorbing light and began producing calcium carbonate by cementing the sand particles together. Calcium carbonate is the main ingredient present in cement used for constructing buildings. However, the process was slow, as per The New York Times.
So, Dr Srubar came up with an idea to add gelatin to the mixture as a resolution to make the matrix (being produced by bacteria) stronger. He had previously worked with gelatin which is a food ingredient that dissolves in water. And when cooled, it forms special bonds between its molecules. Hence, it can be used at cool temperatures that are favourable for the bacteria as well.
The idea of using gelatin fascinated everyone else in the research team. Going ahead, gelatin was added to the mixture. The mixture was poured into moulds and cooled in the refrigerator. Consequently, the gelatin formed bonds “just like when you make Jell-O,” Dr Srubar stated. The result was that it teamed up with bacteria to help build a living concrete that grows faster and stronger. Knox brand gelatin was used by the researchers to dissolve it in the solution with the cyanobacteria.
The Concrete’s Potential As A Building Material
In approximately 24 hours, the mixture produced concrete blocks in the shape of the moulds used by the research team. These included two-inch cubes, shoe-box size blocks and truss pieces with struts and cutouts. Though the living concrete is weak compared to the regular one, individual two-inch cubes were strong enough to endure a person’s weight. The blocks of shoe-box size showed potential for its use in real construction.
This living material is stored in relatively dry air at room temperature. At this point, the blocks reach their maximum strength over time and gradually the cyanobacteria begin to die out. But after a few weeks, it was noticed that the blocks are still alive. When again these bacteria were exposed to their favourable temperatures and humidity, many of them regained life.
In fact, approximately, 9 to 14% of the bacterial colonies were still alive in three different generations in brick shape after a period of 30 days. The entire process has been published in the journal Matter. The Department of Defense has shown interest in using the reproductive ability of these living building materials especially for construction in remote environments. The material could be of great benefit while constructing buildings in deserts where construction is a complex undertaking.
As per Dr Srubar, they believe that this living material is specifically suitable in environments where the resource is scarce. He also made a note on using the material for human settlements on other planets. As far as efficiency and sustainability are concerned, this living building material could contribute generously. Right from production to construction and use, it would significantly reduce the ECE.
Moreover, it could also sense and interact with the environment. For example, living bricks could change colour to show the presence of dangerous toxins in the surrounding, and potentially feed on them. Further, Dr Srubar also noted that if we can grow our materials biologically, then we can produce at an exponential scale. But there is still one challenge hindering the progress.
According to researchers, cyanobacteria requires a humid environment to survive and reproduce. This is something not feasible in many regions across the world. However, they are working to engineer microbes that show more resistance to dry conditions and remain alive and functional. If that is possible, the smart city concept might become more sustainable in the coming years.