Not only wood or clay are available as sustainable building materials. Light, non-toxic and biodegradable materials can also be produced from specially treated mushroom networks. This natural substance is even suitable for efficient fire protection. This has now been shown by Australian researchers led by Tien Huynh at RMIT University in Melbourne, who produced flame-retardant thin panels from fungal networks. The team hopes that their development could replace conventional, hazardous building materials that contain asbestos or polybrominated diphenyl ethers (PBDE).
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For their series of experiments, Tien Huynh and colleagues cultivated pillar fungi (Basidiomycota) on liquid molasses, a by-product of sugar cane refining. The microscopically fine, filamentous hyphae of the fungi formed a mycelium, which the researchers treated with sodium hydroxide. This converted the chitin it contained into the biopolymer chitosan. The researchers then peeled the mycelium from the molasses, let the material dry and pressed it into millimeter-thick layers.
“The material deleted itself again”
In order to obtain a flame-retardant building material from these layers, they exposed it to flames at high temperatures of around 800 degrees Celsius for a short time. “The material caught fire, but extinguished itself after a second,” says Tien Huynh. The chitosan charred on the surface and formed a protective layer that prevented further burning of the mushroom material.
With this property, the biological material could be used as a flame-retardant building material. However, before it can be used, a quick and inexpensive process would have to be developed in order to be able to produce large quantities of the mushroom building material. “Because mushrooms grow slowly, it’s not easy to produce large quantities,” says Huynh.
(jl)
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