As a population, humans are becoming increasingly aware of the need to consider greener alternatives in everyday life to reduce pollution and global warming, from how we generate energy to phasing out single use plastics.
The construction industry is no exception to this trend of change, and is constantly seeking alternatives to conventional building materials. The requirements of such a material are that it is environmentally sustainable, efficient and cost competitive. The humble mushroom, or more specifically its mycelium, could fit the criteria.
What is Mycelium?
Mycelium is the vegetative part of the fungus that grows beneath the surface and absorbs nutrients. It easily colonizes soils and other substrates, and forms a dense network that holds together huge amounts of topsoil; in effect, it acts like a glue that binds different natural particles. Mycelium is vital to terrestrial and aquatic ecosystems where their primary role is to decompose organic compounds, such as plant materials, and return them to the environment while also releasing carbon dioxide into the atmosphere.
When dried, mycelium’s branching, thread-like hyphae can form a light, strong, water-resistant, fire and mold-resistant material. It can be grown and transformed into building blocks of different shapes that are sturdy, resilient and bulletproof. Dried mycelium can withstand high temperatures, traps more heat than fiberglass and pound for pound has a consistency stronger than concrete. Furthermore, its 100% organic and compostable once its useful lifetime is over.
Growing of Mycelium
In order to grow a mycelium block, organic matter, a substrate – often agricultural waste like rice and wheat husks, sawdust, woodchip waste, cardboard and coffee - and a small number of mushrooms are needed. The choice of substrate is important as different substrates impart different mechanical properties and thermal and water insulation qualities on the resulting material.
The substrate is injected with the mycelium, which consumes the substrate’s nutrients, and grown into the solid blocks of cells confined by shaped molds over several days. Incubation length depends on the strain of mushroom – often oyster mushrooms due to their speed, but many other strains have been successfully employed too – as well as environmental temperature and humidity. Mycelium can be hard to tame, after all it is a living growing material. A careful balance must be found for optimal growth; faster growing stains are less open to infections which can occur at high temperatures, but too low and growth is slow. Experiments have shown that more moisture and less air results in a denser finished product.
Interestingly, if two living fungal bricks are placed together within hours they will fuse into one, with incredibly strong bonds. Mycelium growth is only halted by drying or curing the bricks, which are cooked at 70-90 °C after a pre-drying stage. The resulting rigid structure can then be sanded and painted to resemble other building materials, but the mycelium must be completely dry before this to prevent new mushrooms from sprouting!
Mycologist Philip Ross had been experimenting with fungi and mycelium in art installations for over two decades when he was approached by companies who saw the potential of his environmentally sustainable and unexpectedly sturdy building material. Realizing his blocks could be used outside art, he patented his materials and founded MycoWorks, a group of scientists, engineers and designers transforming agricultural waste into robust building materials.
Issues to be Addressed
Mycelium technology has a lot to offer but is still in its early stages and there are many problems still to address. For example, the material’s water-resistance decreases over time and it becomes susceptible to mold and humidity. If away from the ground and properly maintained in favorable and stable conditions, mycelium blocks could last up to 20 years, but this decreases to around six weeks if in contact with the ground.
For this reason, mycelium panels could be used for insulation to replace traditional synthetic materials like polyurethane. It is not exposed to the outside environment and so degradation is slower, but it is still subject to humidity and mold, so requires a protective layer.
Mycelium grows rapidly under a wide variety of conditions and is a simple, low-cost and low-energy means of material production. For it to become a widely-used building material, it must be accepted not only by industry but by the public. Fungus is often thought of as mold, something unhealthy and dirty, but research disagrees. Mycelium has as exciting future as a building material with many companies testing its properties to discover where it might be a suitable substitute for conventional, expensive, energy-consuming materials.
References and Further Reading