fungus

Ganoderma applanatum bracket fungus growing on a beech tree

Larry Doherty/Alamy

Fungi have helped scientists make a breakthrough in transforming wood into a useful source of clean electricity, which could one day lead to “energy ballrooms”.

The possibility of applying pressure to wood to produce an electric charge, known as the piezoelectric effect, has been discussed since the 1940s and 1950s. However, the vanishingly small amount of electricity the process produces has held back the idea.

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Now, a team led by Ingo Burgert at ETH Zurich, Switzerland, has discovered how to tweak the internal structure of balsa wood to make the piezoelectric output 55 times higher. The solution was to deliberately rot the wood.

Burgert and his colleagues applied a white rot fungus (Ganoderma applanatum) to balsa wood for several weeks. This rapidly decayed the lignin and hemicellulose within the wood, reducing its weight by almost half. They found the sweet spot was six weeks of treatment to create wood that was more compressible – meaning it could generate more electricity from the pressing and releasing action when pressure was applied – without losing its strength.

The team then rigged up nine blocks of the decayed wood, covered with a wooden veneer, to create a prototype “energy floor” that was wired up to power an LED. “It’s clear this is only a first step in this direction. But it’s important to show there’s potential,” says Burgert.

The amount of electricity generated is still very small, just 0.85 volts from one cube of decayed wood 15 millimetres across. Initially, the electricity could power remote sensors, for example ones that detect whether an older person has fallen over, suggests Burgert. However, in the longer run he envisages energy floors such as a wooden ballroom producing a much greater output, and is talking with companies about commercialising an energy wood product.

The development could lead to more buildings being made from wood, which are already being encouraged because wooden structures have a lower carbon footprint than those made from concrete and steel. The UK’s Climate Change Committee has said that the 15 to 28 per cent that wood makes up in construction materials in new homes today should climb to 40 per cent by 2050 to help meet the country’s net-zero target.

Team member Javier Ribera at the Swiss Federal Laboratories for Materials Science and Technology says: “We can do much more than just the traditional use of wood. We can tune the properties, we can do many other things with wood, that could be part of future smart cities or new building materials.”

For now, the technique is only possible with balsa, which Burgert says has a particularly low density and thin cell walls. More research will be needed on different fungal treatments for other tree species.

Xiping Wang at the United States Department of Agriculture, who wasn’t involved in the study, says the results are promising. “The proposed fungal pre-treatment of native wood does represent a breakthrough at the fundamental level,” he says.

Journal reference: Science Advances, DOI: 10.1126/sciadv.abd9138

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