Scientists often talk about fungi in ‘iceberg’ terms, in that what you see above the surface is a small fraction of what lies beneath. Dig into the dirt below a mushroom cup and you’re likely to find a vast network of mycelium, the nutrients and communications system that plays such an important role in ecosystem support.

Not surprisingly, mycelium, with its complex web of branched, tubular filaments called hyphae, has piqued the interest of researchers who recognize its potential to be adapted for structural uses in a built environment.

A team out of RMIT University in Melbourne, Australia, has now chemically manipulated the composition of mycelium to create a new sustainable, scalable and safe fire-retardant material that could be used as effective building insulation (and more).

“Fungi are usually found in a composite form mixed with residual feed material, but we found a way to grow pure mycelium sheets that can be layered and engineered into different uses – from flat panels for the building industry to a leather-like material for the fashion industry,” said Tien Huynh, an expert in biotechnology and mycology, and an associate professor in the School of Science at RMIT.

Building on the team's previous research into the fire-retardant nature of mycelium, published in Polymer Degradation and Stability and Nature’s Scientific Reports, the researchers produced a material that can be layered over flammable substrates. By bioengineering the fungi, they were also able to make the mycelium structure uniform throughout the material, and keep it paper-thin.

When the material is exposed to fire or intense heat, the contact layer of mycelium decomposes into a char. This then thermally protects underlying layers. It acts as a non-toxic and effective buffer, which the researchers say has huge potential as a fire-resistant material used in the likes of building insulation.

“The great thing about mycelium is that it forms a thermal protective char layer when exposed to fire or radiant heat,” said Everson Kandare, associate professor at RMIT and an expert in the flammability and thermal properties of biomaterials. “The longer and the higher temperature at which mycelium char survives, the better its use as a fireproof material.”

The material is safe for the environment and humans, sustainable and potentially able to be produced from renewable organic waste. And unlike many traditional panels, it’s plastic-free so won’t produce toxic fumes when in contact with flames.

“Bromide, iodide, phosphorus and nitrogen-containing fire retardants are effective, but have adverse health and environmental effects,” said Kandare. “They pose health and environmental concerns, as carcinogens and neurotoxins that can escape and persist in the environment cause harm to plant and animal life.

“Bioderived mycelium produces naturally occurring water and carbon dioxide,” she added.

While the slow growth rate of fungi presents a challenge to scalability, particularly in comparison to plastic production, it also might present an opportunity.

“We’ve been approached by the mushroom industry about using their fungal-incorporated waste products,” said Huynh. “Collaborating with the mushroom industry would remove the need for new farms while producing products that meet fire safety needs in a sustainable way.”

The team is now researching bioengineered fungal mats that can reduce flame intensity and boost fire-safety ratings in buildings.

The study was published in the journal Polymer Degradation and Stability.