Swedish researchers have built the world's first model car with a roof and battery made from wood-based carbon fiber.

A joint project of KTH Royal Institute of Technology and the Swedish research institutes Innventia and Swerea, the prototype vehicle represents a step toward realizing the use of new lightweight renewable materials.

According to the researchers, the key ingredient in the carbon fiber composite is lignin, a constituent of the cell walls of nearly all plants that grow on dry land. Lignin is the second most abundant natural polymer in the world, surpassed only by cellulose.

The car's carbon fiber roof and battery electrodes are made from wood. Image credit: KTH.The car's carbon fiber roof and battery electrodes are made from wood. Image credit: KTH. Göran Lindbergh, professor of chemical engineering at KTH, says that use of wood lignin as an electrode material in the car's battery came from previous research he carried out with Innventia. Lignin batteries can be produced from renewable raw materials, in this case the by-product of paper pulp production.

"The lightness of the material is especially important for electric cars because then batteries last longer," Lindbergh says. "Lignin-based carbon fiber is cheaper than ordinary carbon fiber. Otherwise batteries made with lignin are indistinguishable from ordinary batteries."

Eventually, carbon fiber bodywork and batteries could be combined as one to simultaneously manage mechanical loads and store electrical energy, Lindbergh adds.

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