Humans have used bio-based materials for hundreds of thousands of years. These include materials such as timber and bamboo. They are eco-friendly, particularly compared to fossil-fuel products, since they are produced from renewable resources and can biodegrade. But to harvest timber and bamboo, the biological organisms used to produce them die off. However, there is a growing field in biotechnology that explores how living microorganisms, such as fungi and bacteria, could be used for construction. These materials are known as Living Building Materials.
The primary purpose of LBM research is to look for alternatives to fossil-fuel-based materials and replace resource-intensive manufacturing processes. This way, industrial pollution levels can be lowered and carbon emissions can be slashed considerably. These bio-based materials also do not impact local ecosystems through intense extraction and manufacturing since they can be grown quickly in labs. Current LBM research is also exploring how buildings can actively grow, heal and absorb toxins from the air while being inhabited by humans.
One of the ways that living materials can be made is through mycelium. Mycelium is the network-like structure of a fungus. Different species have distinct mycelial properties, which can serve various purposes. For example, fibrous mycelium is more elastic, making it optimal for mycelium-based leathers. Conversely, dense mycelial networks are better suited for construction.
Through its growth, the mycelium fuses and becomes one solid material, growing in size. Once it has reached the desired properties, it is either fully dried or partially dried. Partial drying allows the mycelium to stay alive, but it can be rehydrated for continued growth later on.
Mycelium can be used either as a paste that is extruded using a 3D printer or as mycelium blocks. To create the material, the mycelium is combined with a substrate — typically agro-industrial waste like husks, bagasse, seeds or peels. The substrate serves as a food source for the growth of the mycelial network. This mixture is then 3D-printed or poured into molds.
Mycelium-based materials have several advantages over traditional materials. Firstly, they are lightweight and durable. Though they do not have the same compressive strength as concrete, they still can be used for non-load-bearing structures, such as interior walls.
Additionally, their porous composition makes them an excellent alternative to fossil-fuel-based foam insulation. This is due to their high acoustic absorption, fire resistance and low thermal conductivity. These materials are safe for human exposure, as they are hypoallergenic and do not emit toxins.
Finally, the Life Cycle Analysis methodology indicates that mycelial products are carbon negative. This means that mycelium sequesters more energy throughout its lifetime than it emits, even during the production process. At the end of its lifecycle, the material can be composted, as it is biodegradable and enriches soil content.
Concrete is one of the most commonly-used construction materials worldwide. It is also one of the most environmentally-hazardous resources and accounts for 8% of the world’s total carbon emissions. Though concrete has high compressive strength, it can be prone to cracking in damp environments and weathering. In response to these drawbacks, self-healing and self-growing concrete have been developed. These living concretes use bacteria to seal cracks and grow.
Self-healing concretes use non-harmful bacteria that thrive in extreme environments like volcanoes or alkaline lakes. Some examples include bacterial spores like Sporoscarcina pasteurii and Bacillus pseudofirmus. Green Basilisk is one such product that uses these spores. It incorporates the bacteria into a regular concrete mix. When the bacteria are exposed to water from cracks in the concrete, they produce limestone. This seals the cracks and protects the structure from water damage.
Biomason is another product that uses similar bacteria to Green Basilisk but uses a biomimetic process inspired by coral for the material’s growth properties. Biomason uses sand injected with microorganisms poured into brick molds. These bacteria wrap around each grain of sand and grow a calcium-carbonate coating through nutrients they are fed. Over 72 hours, the calcium carbonate bonds are strengthened and the bricks fuse. The bacteria remain alive but in a dormant state and can be reactivated if necessary. Because of the materials and curing process, Biomason does not require high temperatures and fossil fuels during production, making it a sustainable alternative to concrete.
More recently, soil and seed composites that can be extruded have been produced to create buildings that can bloom. The project features small, 3D-printed structures that are built from a raw mix of local soil and seeds. Once these structures have been molded, the seeds begin to germinate, transforming the soil-based walls into sprouting green facades. Meanwhile, the plants‘ roots form networks within the soil walls and provide structural support.
By incorporating flora into the building process, these extruded forms can be used to absorb carbon dioxide from the atmosphere and create healthy, well-oxygenated spaces that are visually appealing. Once the building is no longer needed, the material can be returned to the environment as organic compost. As this is a relatively new system, it has only been used on very small structures. It still needs requires much research and development to refine the material’s weather resistance and durability.
Living Building Materials, regardless of their bio-base, do have several advantages over traditional construction materials. They have proven various self-healing/growing properties, are safe for human exposure, have a minimal environmental footprint and sequester carbon from the atmosphere.
While we can inhabit buildings made from LBMs, research is still underway to optimize their properties. However, given the increasing advancements in biotechnology, and specifically material science, it is likely that architects will soon be able to utilize these incredible resources for healthy, beautiful and sustainable buildings.
Images via Pexels