When surfer, environmentalist and researcher Amelia Martin set out to make an eco-friendly surfboard, her research took her in an unexpected direction – underground.

Martin is founder of Mud Rat, a company that produces surfboards with cores made from mycelium, the underground root-like structure of fungi. She developed the idea while at the University of Connecticut, where she graduated in 2023 with a degree in environmental studies.

Surfboard cores are usually made of Styrofoam. The rest of the board consists of fibreglass and a resin coating – all of which contribute to ocean pollution. Martin was determined to find a better way.

“Surfboards are so bad in every way when you look into this stuff," she said. “There are always solutions in weird places, like in mushrooms. More people should be looking for those solutions. We need it, the world needs it.”

Martin started with the idea of using plastic ocean pollution to produce more sustainable surfboards. When she hit a dead end with that prospect, she discovered mycelium was a suitable material.

Mycelium has a mesh-like texture, making it very strong, yet still incredibly light. It is a promising alternative material for many items, from packaging to furniture. Potential uses depend on the strain and substrate used, as each will produce mycelium with unique material properties.

“It’s the best biological material to replace Styrofoam right now,” Martin says.

"It’s like a little puzzle. With some mushrooms, you need to see where they grow in the natural environment and that’s what you have to pick out to make your substrate.”

Martin spent years researching and experimenting with growing mycelium to find the ideal mix of properties to replace Styrofoam in surfboards. After growing the mycelium, Martin bakes or blowtorches it to ensure it stays in the rigid root-like stage and doesn’t turn into full-grown mushrooms.

There are some challenges to using mycelium to replace Styrofoam. Their molecular weight is slightly higher, which is a major consideration for a product like a surfboard that needs to float. It is also less easy to shape - but Martin has found ways around these problems, particularly being able to sand mycelium into the desired shape.

“We’ve been working on that since the beginning, so that’s our pull right now,” she says.

Martin placed third in the University of Connecticut's Innovation Quest competition, which helps aspiring inventors and entrepreneurs. She is now pursuing her master’s degree in plant science, after which she hopes to run Mud Rat full-time.