"A masterpiece of joining technology will cause a real headache in terms of recycling"
- 114 Downloads
Lightweight design is changing the mix of materials used in the car. Established metallic materials are being joined by composites such as CFRPs and sandwich materials. This is a challenge for the recycling industry, as Ansgar Fendel, Managing Director of Remondis, explains in the interview. It will become increasingly difficult to achieve the required recycling quotas for end-of-life vehicles in coming years.
lightweight.design: Lighter vehicles consume less fuel and give off fewer emissions. At the same time, increasing use is being made of fiber composite materials or plastic-metal hybrids. Do you think that lightweight design is an environmentally friendly technology?
Fendel: That's an interesting question to which there is no easy answer. The argument is plausible from the perspective of reducing emissions and fuel consumption, but from a recycling perspective, the situation is clearly different. It is apparent that the increased use of lightweight design increases the complexity of the material mix, shifting it towards plastics, lightweight metals and composite systems. Vehicles from previous production generations, in contrast, contain a great deal of steel. Old vehicles reach us as a single mass made up of cars from many different production generations whose years of manufacture are in some cases decades apart. On the other hand, every vehicle has its own very special mix of materials. The problem is that the cars do not come sorted by model and construction method. This mass can no longer be separated under production conditions using a shredder, either. In this complex mass, lightweight design leads to a further - and by trend ever increasing - worsening diverseness of the material mixture. Growing heterogeneity in recycling processes results in increased energy consumption.
As someone who separates waste, I know that it is easier to recycle materials if they are collected by individual type wherever possible.
The problem is likely to be exacerbated by the increasing use of hybrid materials.
That's right. If you have children, you will be familiar with the phenomenon where the chaos of a child's room is the most stable of states, while tidying up always makes huge demands on parents' nerves. Following the second principle of thermodynamics, it is exactly the same with processing old vehicles: they come to us in a largely chaotic state. We generally need mechanical energy to process and sort scrap cars. The extent to which separation can be performed very much depends on what level of energy input is economically viable. Entropy sets us a natural limit for recycling.
Is it not possible to use improved processes to gain control over the recycling of hybrid materials?
Breaking down scrap cars, for example through shredding - like the disassembly of the car system - into constituent parts, and subsequent sorting for further use is a very energy-intensive process. It is difficult to cleanly separate conglomerate materials like metal-plastic composites or polyalloy components, if at all. The depth of the separation processes is currently coming up against economic limits, and from a certain point onwards it is simply too costly with the currently available technology.
Should the use of certain combinations of material simply be banned?
No. That would definitely be the wrong approach. Our customers need to develop products for which there is demand and are successful in the market. We do not wish to influence the development and specific design of products. We are only trying to point out where difficulties might possibly arise during subsequent recycling.
Composite manufacturers and users are generally optimistic about the recyclability of their materials.
That's not surprising as individual components can always be recycled if cost is no obstacle. In reality, things look very different unless specific production waste is involved. Take the example of CFRPs. With CFRPs, it is for example possible to use pyrolysis to isolate the carbon fibers from the plastic matrix. However, the process is highly complex, capital-intensive, and requires pure CFRP waste that needs to meet certain criteria. And then there's a difference between the recovered fibers and original primary fibers. Now imagine a car body where CFRPs have been used and which is also probably painted. You face two problems here. What you get is not a single car body containing the CFRP components, but rather an indeterminate mass including also other, possibly compacted, scrap vehicles as supplied to you by the car breakers. Added to that, the CFRP components are then located in positions in the car where we cannot recognize them in our day-to-day operations. Nevertheless, you need to extract the CFRP components in a highly concentrated and pure form. Obviously, here you very soon come up against the limits as to what is currently technically and economically feasible. And then CFRPs are closely linked to the special fact that thermal reutilization is currently very difficult to perform, as waste incinerations plants refuse to accept CFRPs for a variety of reasons.
So, it's not possible to get hold of the continuous filaments in practice at all?
In my opinion, recovering sufficiently long and undamaged filaments from heterogeneous waste mass in a commercially viable way is an extremely difficult undertaking that has not yet been satisfactorily solved. As soon as breaking or shredding are applied in the recycling process, which is the case with car bodies, CFRP components may potentially also be disintegrated. Even if you succeeded in producing a CFRP concentrate, you would also need to have suitable methods for laying open the pure, undamaged filaments without any residues left on them. With that a second fundamental question arises irrespective of whether the coating is destroyed or not. How intact is the filament itself following this pretreatment, and how can it be reutilized later? Nevertheless, I basically think that there is a technical solution, but it falls through due to the reluctance of the market to pay for it as well.
Is lightweight design therefore not yet mature enough for industrial recycling?
Lightweight design and its impressive development momentum are bringing recycling up against limits that we currently feel are unsatisfactory. When we recycle PE or PP, for example, we know that the plastics need to be concentrated to at least 94 % from packaging waste in order to be able to recycle them. This means that we place high demands on the purity of recycled material in industrial recycling processes. Lightweight design is inconceivable without joining technology, and this is becoming increasingly efficient and perfect. At the same time, this represents one of the most massive challenges for us. A masterpiece of joining technology will cause a real headache in terms of recycling. Take the example of steel-aluminum welded connections. It is no longer possible to separate them into aluminum or steel. A steel-aluminum particle can then decide whether it would prefer to be magnetic or not. Separating sandwich structures into discrete materials is also impossible, for example when steel sheets are perfectly combined with layers of plastic.
It sounds as though the idea of closed substance cycle waste management is gradually being dropped.
I would definitely deny that. We're working on interesting processes that we can use to get around the increasing heterogeneity of waste flows. One approach, for example, is to break up suitable materials at the molecular level in order to then reuse them as raw materials in production. Or take metals. With metals we have already begun to separate them according to the type of alloy. There is a great deal of development potential here.
How can this potential be exploited?
We need to network all the businesses along the entire process chain to a far greater degree. In my view, the rapid exchange of information between the sectors needs to be intensified. Even if it is just to gain an early understanding of what new materials will soon enter the market and what possibilities or even restrictions will arise for recycling. I also think it is essential for all partners to be willing to engage far more in the use of recovered raw materials. They would then find more broadly-based solutions for their use. Production processes require raw materials with product constancy. It is our duty to achieve this with recovered raw materials. However, recovered raw materials may not have the same properties that we are used to from primary raw materials. I think it is essential for production companies to be willing to proactively engage with this issue in their operations and to adapt their processes in a reasonable way.
It is probable that progress can be made in networking companies for recycling metal alloys in a better way, but CFRPs remain a problem. What is the situation with glass fiber-reinforced plastics?
They are not that straightforward, either. Glass fiber-reinforced plastics have been around for a long time, and yet I know of no process for recycling GFRP materials that has seen any real market take-up. This is worrying considering the large number of rotor blades that will be replaced on wind turbines in the coming years. The current state of the art is to crush the rotor blades down and to make use of them in the cement industry, in waste incineration plants or in waste-to-energy plants. Besides the thermal value of GFRPs, the cement industry can also potentially use the glass fibers as raw material for silicate base. However, we are already seeing recycling bottlenecks here. We also expect the number of rotor blades to increase in the future.
According to the EU's End of Life Vehicle Directive, 85 % of a vehicle is to be recycled or recovered. Is it becoming increasingly difficult to meet this recycling quota?
Yes, definitely. Especially the national requirement of 95 % or 85 % reuse and material recycling. We expect it will be increasingly difficult to achieve the required recycling quotas for the vehicle generation that came onto the market around the turn of the millennium - simply because the mix of materials used in these vehicles.
Is the automotive industry failing to take these concerns seriously?
In the area of fiber composite materials, automotive companies are also making greater use of thermoplastics as a matrix material instead of thermosetting polymers. Is this easing the problem of recycling?
Yes, but only up to a point, and it also involves a measure of hope. Thermoplastic composite polymers can be reused with the matrix material. This has already been shown with demonstrators. However, the whole thing is still in its infancy and has to complete its baptism of fire. For this to succeed, the thermosetting polymers and thermoplastics need to be separated and correctly sorted from the waste mixture. In principle it is possible, but it makes the separation process that much more difficult. We could do this, but the extra costs associated with it are not currently covered.
Isolating individual materials is also likely to become increasingly difficult in future. There is a trend towards merging several components into a single unit, the keyword being functional integration.
Functional integration is affecting us everywhere. It results in an even greater diverseness of material combinations, that means there is a very wide range of materials concentrated in a very small space. This is coupled with additional growth in material dissipation. Today we are confronted with an increasing tendency towards such compact structures that now make it impossible to perform selective separation economically. A good example of this are tiny electrical control or drive units that end up after a scrap car has been broken up as extremely fine strands of wire that are virtually impossible to isolate.
Dr. Fendel, thank you very much for speaking with us. |