When you think about strong, fireproof materials for building homes, soft and spongy mushrooms are not the first thing that come to mind. But two new studies show how fungi could be used to make sustainable building materials that reduce the climate and environmental impact of our built environment.
A team from Newcastle University in the UK and Vrije Universiteit Brussel in Belgium have grown fungus together with other ingredients to make a material they call myocrete, which can be used for lightweight construction. In another study, researchers from RMIT University in Australia engineered mycelium—the root-like network that is the foundation of fungal colonies—to create a sustainable fire-retardant material that could be used as building insulation or a leather substitute.
Mushrooms and other fungi usually grow in colonies. When mushrooms sprout up in the soil, they are just the tip of an iceberg. They are connected to a large network of white thread-like structures that grow under the soil or on rotting tree trunks, transporting nutrients to the fungus from the environment.
With myocrete, the UK–Belgium team is trying to address the carbon footprint of the construction industry. Mycelium-based materials have excellent thermal and acoustic properties, which makes them promising for insulation and soundproofing. “They have potential to provide an inexpensive and sustainable class of materials suitable for the replacement of foams, timber and plastics for applications within building interiors,” the researchers write.
In their paper in the journal Frontiers in Bioengineering and Biotechnology, they detail a new recipe for myocrete and a way to grow it in knitted textile tubes to make large-scale components that can take on complex shapes for construction.
The authors combine mycelium spores, grains for the spores to feed on, and paper fibers. They make a paste of those ingredients with water, glycerin and xanthan gum. Then they inject this paste into a knitted fabric mold and place it in a dark, humid and warm environment conducive to fungal growth. As the spores grow into a dense mass of mycelium, the paste solidifies into a stiff material that takes on the shape of the mold. Finally, the researchers remove the mycocrete from the growth chamber and dry it out.
Tests showed that the new mycelium-knit textile combination was stronger than other mycelium composite materials reported so far. With a system of slender knit mycelium tubes, the team constructed a 1.8m-high self-supported freestanding arched dome.
RMIT engineering professor Everson Kandare and colleagues, meanwhile, tapped into the fire-retardant nature of mycelium. When exposed to high temperatures, mycelium forms a char that protects whatever is underneath from fire. “The longer and the higher temperature at which mycelium char survives, the better its use as a fireproof material,” said Kandare in a press release.
Kandare and colleagues grew mycelium at different temperatures, growth times and salt concentrations to see how it affects the microstructure, and the physical, chemical and thermal properties of the fungus. By finding the right conditions, they designed a paper-thin, uniform film of mycelium that can layer on other substrates as a thermal protection layer. The material forms a char at very high temperatures of over 300°C. The details appear in the journal Polymer Degradation and Stability.
Mycelium is an “environmentally friendly and potentially a sustainable fire retardant,” the team writes. The phosphorus-based fire retardants commonly used today are potential carcinogens and neurotoxins, and they can escape and persist in the environment, harming plants and animals.
- Romy Kaiser et al. BioKnit: development of mycelium paste for use with permanent textile formwork. Bioeng. Biotechnol. 2023.
- Nattanan Chulikavit et al. Engineering mycelium fungi into an effective char-forming thermal protection material via alkaline deacetylation. Polymer Degradation and Stability, 2023.
Image: ©RMIT University