Creating carbon fibre from plant waste for cars that grow on trees

Researchers have found a cheaper and more sustainable way to make carbon fibre, from leftover plant residue.

The strong, lightweight material is often used in planes and cars, and is usually made from a substance called polyacrylonitrile (PAN), an expensive non-renewable polymer. “PAN can contribute about half of the total cost of making carbon fibre,” said Jinxue Jiang, a postdoctoral fellow at Washington State University. "Our idea is to reduce the cost for making carbon fibre by using renewable materials, like biorefinery lignin.”

Lignin is a component of the cell walls of plants and trees – when they’re turned into paper or biofuel, it’s left behind, and is usually burnt or binned. In the past, researchers have tried to make carbon fibre from 100% lignin, but have found it too weak for use in the automotive industry.

The team from Washington State instead combined lignin with PAN using a process called melt spinning. “You elevate the temperature of the polymer blend until it melts, so it can flow,” explained Jiang. “Then you spin these polymers until the fibre forms.”

The team tested a number of different ratios of lignin to PAN, and found they get away with as much as 20 to 30% lignin without sacrificing the strength of the material. They say their fibres could be used in the automotive industry and plan to take them to a car plant to test them in a real-world scenario.

“If we can manage to get a fibre that can be used in the automobile industry, we will be in a good position to make biorefineries more economically viable, so they can sell what they usually would discard or burn,” said Birgitte Ahring, the lead investigator on the project. “And the products would be more sustainable and less expensive.”