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Researchers Have Found A Way to Make Carbon Fiber From Plants

On Sunday, February 4th, 2018

Carbon fiber is glamorous. It helps shed precious pounds from performance-focused cars like those from McLaren (its carbon Monocell is pictured above) as well as upmarket eco-warriors like the BMW i3, and it is increasingly applied as merit-badge splashes of decor on sporty trims of myriad other vehicles. But it also has a dark side in that it’s by no means an eco-conscious material to produce.

Carbon fiber

Carbon fiber’s large ecological footprint centers around the way in which acrylonitrile, the base material for commercial carbon fiber, is currently made: from petroleum, using a process that uses quite a bit of energy, requires an expensive catalyst, and yields hydrogen cyanide, a toxic byproduct. This also helps explain carbon fiber’s high price, as just the acrylonitrile itself—two pounds of which are required for each pound of finished product—accounts for more than half of the production cost of carbon fiber.

Fortunately, this issue is at the center of biomass research that aims to make significant cuts to costs and eventually to wean carbon-fiber production off oil entirely. Researchers at the National Renewable Energy Laboratory (NREL) last month announced that they have created a new catalytic process that is both compatible with renewable feedstocks and has a far better yield than the existing process—98 percent versus 80 to 83 percent. The research team estimates that, using cellulosic biomass (from wood, grasses, or even paper pulp) or starch-based sugars, it could lower the cost of making the base material to below $1 per pound.

Growing (Not Pumping) the Materials

That cost target has been among the goals of the Renewable Carbon Fiber Consortium, a research effort with a budget of about $8 million funded mostly by the U.S. Department of Energy (DOE), along with other financial partners that include Ford. Transitioning to variable feedstocks should also make the price itself more stable, as the way it’s produced today leaves it open to fluctuations in typically volatile oil prices. Meanwhile, the demand for carbon fiber is projected to increase by up to 18 percent annually.

The DOE project, which is scheduled to last at least until the end of 2018, is focusing its research on uses for automotive lightweighting. But aircraft could benefit eventually, too.

Carbon fiber lasts a long time, yet it’s very difficult to recycle. In part, that is because reprocessing it often involves breaking the carbon-fiber material away from the polymer it has been bonded to—usually a carbon-fiber composite (CFP) or carbon-fiber-reinforced plastic (CFRP)—shredding the fiber, and then trying to realign the recycled fiber into a new material, which inevitably has less strength. One of the few exceptions would be the forged carbon-fiber composites that Lamborghini has developed and is beginning to use in its latest cars.

Researchers have tried other plant-derived feedstocks in the past, including lignin, pitch, and rayon, but the results haven’t been favorable. The next phase of the DOE research is to scale the process up to 110 pounds of production material and test a carbon-fiber component made with it. If these researchers have cracked the code for making carbon fiber to the same strength as the current stuff, the material could become even more widespread—and save a lot of oil to boot.

Posted in Auto News

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