Natural Materials: Algae, the Marine Bioconcrete Alternative?
Algae have been some of the most intensively researched organisms for innovative technologies ever. From their potential as a biofuel to fertiliser, nutritional supplements or pollution treatment, the next great promise for these photosynthetic marine organisms is in construction materials.
Carbon Absorbing Phenom
The quantity of carbon sequestered by algae cultivations is incredibly high. Algal organisms absorb carbon and produce oxygen through photosynthesis just like terrestrial plant life, except at a much higher efficiency. For comparison, one hectare of forest fixes around 3 tonnes of CO2 per year, whereas one hectare of algae cultivation fixes around 200 tonnes of CO2 per year. Not only do algae cells fix carbon at a very high efficiency but they can grow exponentially too, they can even double in volume every 4 to 6 hours! This allows them to consume huge amounts of carbon in such a short period of time.
Algae cultivation’s high carbon fixing rate means that they’re an incredibly useful plant from which to create building materials. To add to their usefulness, algae farming doesn’t take up arable land and doesn’t need to compete with agriculture or food production.
How can Algae create a construction material?
As surprising as it may seem algae can be used to produce a cement-like substance that can be made into bricks.
This is done through a process called biomineralisation in which algae absorb calcium ions from their environment.
Algae, like many other organisms, can absorb calcium ions from their environment, typically from the surrounding water. Calcium ions are essential for various cellular processes and are readily available in aquatic environments.
Algae also secrete bicarbonate ions as part of their metabolic processes. These bicarbonate ions can combine with calcium ions to form calcium carbonate, which is a common mineral found in nature. Algae can create what is called an extracellular matrix (a structural framework outside their cells) to support their growth and provide protection. This matrix is often composed of various organic molecules, including proteins and polysaccharides (a common type of carbohydrate).
Within this extracellular matrix, the algae can control the local concentrations of calcium ions and carbonate ions. When these ions reach a certain concentration, they can spontaneously combine and precipitate as calcium carbonate crystals.
Over time, as more calcium carbonate precipitates and accumulates, it can form a solid, cement-like material within or around the algae’s structure. This material can help bind the algae to substrates, such as rocks or other surfaces in aquatic environments, and provide structural support.
This naturally produced binder can then be used as an SCM to provide low embodied carbon concrete.
Among many different areas of research and development that focus on algae solutions, air purification has been prominent. Since algae sequester so much carbon and filter air, an innovative new idea has been constructed by Ecologic Studios.
By installing internal structures with microalgae cultures, an effective bio-based air purification system can be produced. Ecologic have created a few prototypes of this air purification system. In an office in Switzerland, they have hung a series of microalgae cultures in their installation named AIRoffice.
This is also not their only biotech air purification system, they also installed AIR Bubble in Cairo, an inflatable structure that has filtering microalgae in its membrane that also doubles as a fun bouncy castle for children. Ecologic claims that the air inside their inflatable biotech garden is 85% purified of urban pollutants. These gardens also embrace circular principles as the algae can be reused to produce biopolymers.
Algae construction materials are a very recently developed product and large-scale production of the product has not happened yet. Prometheus Materials is one of the first brands to successfully develop and produce algae bricks. The brand formed out of a research project at the university of Colorado in 2021 and is generating significant media attention for its product ProZero.
ProZero is a bioconcrete solution made from a mixture of coral reefs, shells and microalgae as a binder. Prometheus claim that the mixture is not only zero-carbon but provides thermal insulation twice as good as conventional concrete, sound absorption 12x better, a bond strength that’s 3x better and is also 15-20% lighter. Additionally, all their products are segmented or modular making them easier to install, faster to construct and more practical to reuse/recycle. They also claim that their production process is easy to upscale, all of which suggests that their product has ground-breaking potential.
Prometheus also has some backing from influential investors, such as the Microsoft climate innovation fund. Nonetheless, their product is still far from the mainstream but is prepped to make big changes in the built environment.
Another brand that has developed an inventive algae-based solution is for Tomorrow. Their product, Sargablock (from Sargassum meaning seaweed), uses brown seaweed washed up on the shores of the Caribbean and turns it into construction blocks. The idea was started by Mexican entrepreneur Omar Vasquez who has been dubbed “Mr Sargassum” as a result and has even received an Insider Business report. He has built as many as 13 houses for low-income families using this bio-waste material.
Again, this algae material is not yet replacing standard concrete in large urban development projects but given time and further R & D could find some larger applications.
The Future of Algae Solutions
It is too soon to make any clear predictions on the future of algae construction materials as there is no large-scale production but there is certainly huge promise. Algae is fast to grow, doesn’t use up agricultural land, sequesters carbon, has high recyclability potential and seems to offer impressive structural properties when compared to standard concrete.
The fact that algae construction solutions are mostly SCM-based, bodes well for their future. SCMs are becoming very popular in the construction industry as they allow a material to share the similar useful properties of traditional concrete yet also be low carbon too. Concrete has been notoriously hard to replace since it boasts such impressive strength and durability yet is infamously harmful to the planet, accounting for up to 8% of global GHG emissions.
The creation of low-carbon SCMs seems to hold the key to lowering the colossal emissions of the concrete industry and is being used to achieve a range of sustainable concrete products such as Olivine concrete.
Algae products are already a multi-billion dollar industry, that is expected to grow rapidly. Most of these products are not construction-based, but this means that there is already mass algae cultivation for which to lay the foundation of large-scale algae materials production.
The future of Algae construction seems poised for success and this Biobased low carbon material is greatly needed by the concrete industry that is aiming to be net zero by 2050.
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