It’s been a strong week for alternative materials here at The Fifth Estate. First there was the story that adding carrots to concrete could make it stronger and greener. Then there was the company making building panels out of hemp, with the promise to soon be 3D-printing hemp houses.

Now researchers, including some from RMIT and UNSW, have developed a low-energy, zero-carbon, fire-resistant building material from mushrooms and rice that could replace fossil-fuel-derived products and also tackle problem waste streams.

Fungal brick prototypes made from rice hulls and glass fines waste.

The Trametes versicolor fungus can be bound with agricultural and industrial wastes to form lightweight bricks. In research published in Fire and Materials, scientists used the fungus to bind rice hulls and glass fines (a problem waste stream), and baked the material to create lightweight, strong and fire-resistant bricks for use in non-weathering, non-structural and semi-structural construction applications.

The “mycelium composite” product proved a safer and “very economical” alternative to highly flammable petroleum and natural gas-derived synthetic polymers and unprotected engineered woods used in insulation, furniture and panelling, the researchers said.

Some of the composites tested were up to 31 times cheaper than extruded polystyrene and particleboard.

Regarding fire safety, the mushroom bricks had much lower average and peak heat release rates and longer time to flash-over. They also released significantly less smoke and CO2, though carbon monoxide levels fluctuated.

“Their widespread use in civil construction would enable better fire safety in buildings,” the researchers concluded.

Rice hulls, glass fines and the mixture of rice, glass and fungus, before baking

Thy also said their product was less appealing to termites.

On the sustainability side, as well as involving low amounts of energy to produce and having the potential to replace fossil-fuel-derived building products, the bricks also provide a home for two problem waste streams.

About 167 million tonnes of rice hulls are produced a year globally, considered a low-grade agricultural byproduct that is largely discarded as waste. Glass fines also account for 20-29 per cent of Australia’s 600,000 tonne a year glass waste. The bricks could prove an economical way to lock up these waste streams.

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