4/11/2019

Carbon Fiber and Recycling

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One of the key drivers for the use of carbon fiber composites is that the materials are both strong and light.

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One of the key drivers for the use of carbon fiber composites is that the materials are both strong and light. Yet there are a couple hits they take, which is that they are expensive and while a lighter vehicle can mean less fuel is burned to propel it and consequently there is an environmental benefit at the tailpipe, when it comes to looking at the material on a life-cycle basis, it isn’t exactly environmentally benign. According to a presentation made by Marco Gehr, COO of ELG Carbon Fibre Ltd. a couple years ago, “Carbon fiber raw material production requires up to 280 MJ/kg (5-6 times of steel); only less than magnesium and more than aluminum.” (Wonder why the steel folks are in favor of life-cycle analysis?) Evidently, carbon fiber components are not necessarily “green,” light weighting notwithstanding.

According to the folks at ELG, the demand for carbon fiber on a global basis in 2020 may be on the order of 180,000 metric tons.

ELG1

(Images: ELG Carbon Fibre)

But here’s a startling statistic from the firm: “current manufacturing technologies result in approximately 30% of the overall carbon fiber demand becoming waste during the conversion and component manufacturing phase.”

So you have a tremendous amount of energy expended to make it, then a solid percentage of that made material is scrap. Which is even less green.

ELG Carbon Fibre operates what it claims is “the world’s first and largest carbon fibre recovery plant.” It is in the West Midlands of the U.K. (which explains why “fiber” is spelled the way it is in some cases here).

It uses a pyrolysis process—which uses heat and pressure to chemically decompose organic material—on the collected, processed and prepped material (everything from uncured prepregs to end-of-life components).

The output of that process is then transformed into milled fibers, nonwoven mats, pellets, and chopped fibers, which can be used for the production of new parts.

ELG2

Gordon Murray Design, which has developed a low-volume city car, has determined that making a body panel with recycled material costs €30 vs. €300 for one made with a new woven prepreg. That 10X difference is fairly compelling. And by reusing the material, the greenhouse gas emissions are greatly diminished.

(You can learn a whole lot more about ELG and other composites-related objects, materials and undertakings from our sister publication CompositesWorld.)

All of this would have passed us by were it not for the fact that Mitsubishi Corp. has recently acquired 25% of the shares of ELG Carbon Fibre.

Now given that Mitsubishi has under its rather extensive umbrella everything from shipbuilding to banking, from pharmaceuticals to machine tools, the fact that Mitsubishi Motors is in there may not be even remotely considered in the context of ELG and the recycled carbon fiber materials.

But say that it is. Potentially the OEM could have a leg up on virtually every other mass-market vehicle manufacturer on the planet.

We’ll have to wait and see.

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