We've seen bike helmets with wooden shells before, and we've also seen foam made from wood pulp. Now, however, Sweden's KTH Royal Institute of Technology has teamed up with Stockholm-based startup Cellutech to combine the two. The result is a helmet made entirely from wood.

Known as Cellufoam, the shock-absorbing foam in the helmet is said to be similar to Styrofoam – except it comes from a renewable source, and it's biodegradable. Like similar products we've covered before, it's made by mixing a foaming agent with cellulose nanofibers derived from forestry industry byproducts. This means that trees don't need to be cut down specifically for foam production.

Even the straps are wood-based, being made from a heavy-duty paper.

The helmet was designed by Rasmus Malbert and Jesper Jonsson, from design studio Materialist. It was made as part of the Ekoportal2035 project, which explores the concept of "a biobased future." There's no word on possible commercialization.

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