Signed by fungi

Air-conditioned: Lewis Douls checks the boards colonized with the fungus, which are maturing in the climate chamber. Image: Empa

Nothing is left to chance in the production of spalted wood. The boards, which can be up to two and a half meters long, are brought to the correct humidity in a vacuum chamber, sterilized and inoculated with the fungus. They then spend several weeks in a climate chamber while the fungus etches its markings into the wood. With the know-how gained during the project in the Empa laboratories, Koster AG Holzwelten can control and refine the appearance of the melanin pattern.

Once the fungus has completed its work, the wood undergoes a technical drying process, which simultaneously kills the fungus. "The special thing about this particular fungus is that it does not break down the heavily lignified areas of the cell wall; the wood thus retains a high degree of flexural strength," explains Schwarze. The resulting spalted wood with its dancing lines is particularly suitable for decorative applications, for example for furniture, interior design, musical instruments and even jewelry. Inquiries are already piling up, reveals Jakob Koster, who has now handed over the management of the company to his son and is devoting himself entirely to sales and innovation.

Numerous hardwood species are suitable for the production of spalted wood. Koster AG Holzwelten relies on native species such as maple, beech, ash, linden and poplar. Today, these types of wood are mainly used for heating, since they are not considered attractive enough for other applications. "Wood is an important CO₂ sink – as long as you don't burn it," says Empa researcher Schwarze. Refining locally produced wood is also a sustainable alternative to exotic import timber. "We have to learn to develop innovative products with our local resources in Switzerland," summarizes Koster.

The pattern does not remain on the surface, but runs through the entire thickness of the spalted board. Image: Empa

Innovation needs more than just a clever idea: It takes a lot of hard work to turn promising laboratory results into marketable products. No one knows this better than Lewis Douls, who has accompanied the spalted wood project through this transition. The chemist originally came to Empa on a civil service placement. However, he was so enthusiastic about the work in the fungal laboratory that he stayed at the research institute – until he moved to Koster AG Holzwelten two years ago to take over the upscaling of the spalted wood production.

No easy task: Cultivating fungi in a controlled manner is a high-tech undertaking. The conditions that the melanin-producing sac fungus needs to grow are also ideal for countless other types of fungi, and fungal spores are everywhere. "Sterility was the biggest challenge," recalls Douls. Another challenge was cost-effectiveness: A fully equipped biotechnology laboratory does not simply spring up like a mushroom. Expensive equipment, such as autoclaves for sterilization or vacuum chambers for wood humidification, were needed. Here, however, Koster AG Holzwelten was helped by its inventive spirit – and a good dose of luck. The company was able to take over a large part of the climate chambers from a retired mushroom grower. The laboratory equipment came from ETH Zurich, which had commissioned the company with a renovation. What's more, Douls was able to optimize certain process steps, such as the sterilization of the boards, so that a large autoclave was no longer required.

Francis Schwarze is impressed by the effort his project partners have put into the facility. "It's not a matter of course for an SME to acquire so much knowledge and to set up its own laboratory," says the researcher. Schwarze and Douls agree that the company is now even better equipped for cultivating the wood fungus than the Empa laboratory where the project started.

With the challenges overcome, the production line is up and running, and the fungi are doing their decorative work in the air-conditioned chambers. The next step, as Jakob Koster knows, is sales. After the long development period, the new product must become commercially viable. However, the project partners already have new ideas for the future. For now, they are willing to reveal just this: The perfect combination of wood and fungus can do so much more ...