Can the Auto Industry Learn about Recycling Composites from the Aircraft Industry?

Automotive Composites project manager Anca Scurtu interviewed Dr. Tom Turner of the University of Nottingham. He is currently a Principal Research Fellow within the composite materials group and project manager of the Boeing strategic collaboration in carbon fibre recycling.

"An end-of-life vehicle view doesn’t promote a lifecycle view, it just promotes good disposal of materials at the end-of-life."

Automotive IQ: Recycling composites seems to be an issue for the auto industry? What are the major limiting factors?

Dr. Turner: There are several limiting factors. Historically, one of the problems has been in making an actual recycling process that will allow the material to be recycled and cope with materials that you don’t want to go through the process in an automated and cost-effective way. Other problems include the energy-intensive nature of the process, and the manual labor-intensiveness.

Most recycling solutions are based on having a similar material coming out of the process that you are putting in. For example, you can use recycled paper for the same applications that you could the original paper product, maybe at a slightly reduced cost, and a slightly reduced quality. The idea is the same with glass.

However, for fibrous composites, that's not the case. You are fundamentally changing the structure of the material, reducing the fibre length and so the materials that you can make from recycled composites are never going to be the same as the materials you can make from virgin fibre composites with their essentially infinitely long fibres. They are continuous fibres when they go in but whatever happens to them they'll be discontinuous. Therefore, we need to select materials and markets carefully to make use of that composite form which is basically a new material. The third big problem is a slightly more philosophical one. When you recycle a composite you can get fibres back from the material but getting useful products from the resin component of the composite is very difficult. So the commercially running processes at the moment will completely remove the resin and you'll be left with fibres. From an end-of-life vehicle directive point of view that's a problem because if you can't recycle 95 percent of the material because you can only recycle as much as are fibres in the material. In some composites, for instance sheet-moulding compounds, the fibre might only be 35 percent of the volume of the composite. So even in the best case of recycling, you're only getting a portion of the material back out. Those would be my big three problems.

In terms of recycling, the aircraft industry is one step ahead of the automotive industry, how come? Don't they work with the same composites, after all?

That's a really good question. I think the automotive industry is just more reluctant with composites. In aerospace, they’re already using composites for the current generation of aircraft and so they absolutely have to have a recycling solution and if those recycled materials could go back into aerospace in some other non-structural application, the aerospace industry would be happy. But even if they can't, they still need an in-process scrap and an end-of-life material disposal route which is better than landfill.

Whereas for automotive, there's always this big issue where they don't even want composites in the vehicles unless the price is right and unless there's a demonstrable benefit for using composites. For aerospace that benefit is clear for using composites now; for automotive it's not so clear and so there is not enough of a driver to develop recycling processes for materials that aren't really being used at the moment. I imagine that companies currently using composites are either low volume and they're not too worried about end-of-life disposal or they're higher volume but they think that a good recycling solution will be developed by aerospace which they can use a few years down the line. That's my impression. I don't think there's anything fundamentally different about the materials or the technologies that could be used.

How does the type of composite influence the recycling process? Are there any solutions available based on the type of composite or is the approach one size fits all?

It’s hard to know how to categorize the different composites. I suppose fundamentally it’s one size fits all but the processes are just to separate the fibres and resin, remove the resin and recover the fibres in the most useful form possible. I believe the processes that are available differ in their ability to handle different types of material, different contaminants, things like paints, metallic fasteners etc. There’s some difference in terms of part thickness. It’s quite easy to envisage a recycling process where you take rolls of material which are no longer able to be used like pre-preg material and recycle them, remove the resin and then you have a roll of material that can be reused. End-of-life is much more challenging. The recycling processes that are available differ in how well they can handle those issues and how much hand labour is required to prepare the materials for recycling. I would say that for the material structure itself there isn’t much of a distinction to be made on that basis.

We spoke earlier about final products, what kind of viable products can be obtained from recovered fibres?

I think that’s the next big question in composites recycling. I think a few years ago the question was what processes are we going to use, and now there are a few processes available but there’s still work to be done on them. But for me, the question of reuse is the next big thing. There has to be some economic or financial basis for reuse. Someone has to make money out of the materials and so this is where a lot of our work is going into and other people will be working on reuse as well. It’s very challenging. My feeling is that it would be nice to envisage a sort of supply chain where materials might come from aerospace end-of-life or aerospace scrap. High-performance composites could then be recycled down to a reduced fibre length and then those materials could be made into moulding compounds that are already used in automotive and maybe come in with a higher performance than glass fibre compounds below the cost of current carbon fibre compounds. I think that would be a nice reuse avenue; and the same corresponding reuse approach with thermoplastics, so instead of putting virgin carbon fibre in a thermoplastic injection moulding compound, you would then be able to put recycled fibre in and make parts for automotive. Again, maybe carbon fibre parts for lower cost replacing glass fibre parts. Those are two obvious reuse routes for short fibres and I think we will be faced with short fibres.

What are the aspects that can be improved when it comes to recycling solutions and implementation? Are they on a research level or are they on a technological one?

I think we’re in a difficult stage where there are processes at research scale which require investment to take them to commercial scale to demonstrate the problems that will be found in real parts. There are processes running at commercial scale where perhaps there aren’t markets there to drive the development further. Those processes are first generation so the processes that are being developed in the research community potentially have better aspects than the current commercial processes either through higher quality fibres, more energy efficient operation, or more automation. These processes have been shown to work in a laboratory but they need to get out there and be commercialized and then, in terms of looking for investment for that commercialization, we have the problem where the market is waiting for a good solution for a downstream material - something that you can actually put into a production vehicle which could actually use up some of the recycled fibre that’s coming at the moment it’s that circular problem of which of these things will happen first. This is why the end-use material is so important because when someone shows that a material can go into a future vehicle made from recycled fibre, that could start the cycle of getting some of these new recycling processes commercialized and out in to the market, then we’ll see what the challenges are.

For me, in terms of recycling process, a lot of the R&D has been done. The problems are with scaling up. There will always be new processes invented and I’m sure there’ll be some new ones coming along in the next five years which may have big benefits, but how will they be commercialized, that’s the big question.

What companies do you think are well-positioned to come up with solutions for recycling composites? I am told that some car manufacturers believe there are currently no viable solutions whatsoever.

That’s quite a negative statement. Personally, I don’t know of anyone in automotive that’s really pushing recycling as a priority and really doing good things, so there’s a big gap there. The main aerospace OEMs have it as much more of a priority. To say there’s no viable solution is too pessimistic.

If the manufacturers who believe there are no viable solutions are referring to the fact that 50 percent of the material on an end-of-life vehicle disappears during the recycling process, then I think they are right that this is a disappointing situation. There will always be some point with composites where you say, we made a very highly optimized part in the first place, we used a composite because there was that synergy of the composite material which allowed a very high performance but that inevitably means it is not as easy to recycle as steel or aluminium.

There’s this need for a real lifecycle view of the recycling process and unfortunately, the legislation that’s in place at the moment doesn’t really consider the lifecycle. This is one of the barriers. An end-of-life vehicle view doesn’t promote a lifecycle view, it just promotes good disposal of materials at the end-of-life. It doesn’t look at the use phase; it doesn't look at whether using the material that's difficult to dispose of.

Actually the benefits over the use phase can be overwhelming for some parts, in which case, you would make the choice to use the material and I think that's the case in aerospace. It almost matters very little whether the aircraft can be recycled at the end-of-life when, if you make it one kilogramme lighter, the benefits over its use phase are absolutely overwhelming. For automotive, I would say it’s right on the edge; you can use carbon fibre, you can show a weight-saving, you can show a use-phase benefit but it’s not as overwhelming as with aerospace. The end-of-life disposal is still a big factor and the manufacturing is still a big factor because the use-phase is less dominant. This is a big issue and it’s a material selection issue as much as a recycling issue specifically. That problem will exist until someone develops really good recycling solutions and in the meantime, automotive will be understandably reluctant.