Sustainable textiles made from mushrooms
It might be time to replace your Fendi handbag with mushrooms, say the researchers. They harnessed the power of the humble mushroom to convert food waste into sustainable faux leather, paper and cotton substitutes.
Presenting their findings at a virtual meeting of the American Chemical Society (ACS), the researchers say this fungal leather takes less time to produce than existing substitutes already on the market, and, unlike some, is 100% biobased.
Their efforts connect two huge, but seemingly unrelated, environmental concerns. Cotton, petroleum-based synthetic fibers, paper and leather are all plagued by environmental issues, ranging from water demand to contributions to climate change and the ethical treatment of animals. During this time, a lot of food is wasted.
In a bid to solve all of the problems at once, lead researcher Dr Akram Zamani and her team in Sweden have developed a range of sustainable materials derived from fungi.
“We hope they can replace cotton or synthetic fibers and animal leather, which can have negative environmental and ethical aspects,” says Zamani.
They are not the first group to have produced fungal leather, but according to Zamani they are the first to have produced a product with properties that can match real leather, and at a production rate that could realistically match the market demands.
Although there is little information available on the production process of existing fungal materials, Zamani says it appears that most are made from harvested mushrooms or mushrooms grown in a thin layer on food scraps or sawdust using solid state fermentation. Such methods take several days or weeks to produce enough fungal material, she notes, whereas her fungus is submerged in water and only takes a few days to produce the same amount of material.
Additionally, some of the fungal leathers on the market contain environmentally harmful coatings or backing layers of petroleum-derived synthetic polymers, such as polyester. This contrasts with the University of Borås team’s products, which consist only of natural materials and will therefore be biodegradable.
“When developing our process, we were careful not to use toxic chemicals or anything that could harm the environment,” says Zamani.
So how do they go about turning mushrooms into materials? It all starts with fattening the mushroom you have chosen.
Mushrooms are hungry little organisms. To feed their cultured fungal strain – Rhizopus delemar, commonly found on rotting food – the team collected unsold supermarket bread, which they dried and ground into breadcrumbs. As the fungus fed on the bread, it produced microscopic natural fibers composed of chitin and chitosan that accumulated in its cell walls.
After two days of feeding, the scientists harvested the cells and removed lipids, proteins and other by-products that they believed could potentially be used in food or feed. But what they were really after was the gelatinous residue left behind – a goop made up of the fibrous cell walls that was then spun into thread, which could be used in sutures or healing textiles and perhaps even in clothes.
In an alternative method, the fungal cell suspension was laid out flat and dried to make materials resembling paper or leather.
Through a series of trial-and-error tests, the team has now developed materials made from multiple layers of these fungal leaves. The composites are treated with tree-derived tannins to give them softness and alkalis to give them strength. Finally, resistance, suppleness and shine are all improved by treatment with glycerol and a biobased binder. The end result is a material that closely mimics real animal leather.
“Our recent tests show that fungal leather has quite comparable mechanical properties to genuine leather,” says Zamani.
The team is working to refine its fungal products. They have recently started testing other types of food waste, including fruits and vegetables – specifically the mushy pulp that remains after juice has been squeezed from the fruit. “Instead of being thrown away, it could be used to grow mushrooms,” says Zamani. “So we don’t limit ourselves to bread, because I hope there will be a day when there is no more wasted bread.”