Yes, you are correct it is chemically possible to recycle these materials. But that doesn't matter as you are probably aware just about because anything can be recycled if you ignore politics and economics.
But we can't ignore politics or economics. Even if plastic recycling is less energy intensive than recycling iron or aluminum, it is far more economically expensive than either. If this was not true then the numbers would tell a different story. But they don't and that's the reason why the majority of plastic that is "recycled" is not actually recycled and ends up in landfills.
The numbers don't lie. Over 88% of steel is recycled, and aluminum is just at 70% Plastic on the other hand doesn't even hit 10%., even the most commonly recycled sub-type of plastic, PET only hits about 30% and this is because it is one of the few plastics that does have a low cost to recycle. Other very common plastics like PVC and PS have much higher recycling costs and don't even hit 1% global recycling rates. The economics boils down to a simple equation, creating new plastic is far cheaper than recycling while recycling steel and aluminum is far cheaper than digging them out of the ground.
Regarding FRP recycling, while it might be possible from a process point of view, it is not economically viable. This is because, unlike common plastics such as PET or even PVC, or PS, which generally have a known chemical composition (although there are slight variations) the composition of FRP (like all composite materials) is tailored to their specific use case at the time of manufacturing. This means that both the mechanical and chemical deconstruction processes can vary widely depending on what the composite is actually made of. It is true that there is continuing research into composite material recycling and processes do exist many of these focus on upcycling, and focus on just a few specific types of composite, (carbon fiber, fiberglass, etc.) while ignoring others that are almost impossible ( thermoset and polymer matrix) and even these less-than-ideal processes are not cheap and require significant additional capital expenditures to implement. Contrast that to plastics and aluminum recycling which have been going on for 50 years and steel which we started to recycle in the late 1800s. These processes are widespread and available all over the world.
If a company wants to implement a car that is recyclable and uses recyclable materials they don't need to reinvent the wheel or even reinvent unibody construction. You could even still use honeycomb construction with aluminum or steel to reduce weight, it's already used widely in aerospace.
But here is the rub, there is nothing sexy about building a car out of steel and there is no way to use it virtue signal. It doesn't make for awesome press releases or blog posts. Which is really what all this is about. And unless Citroen is planning on building a recycling plant and shipping all the cars back to it when they are done to be recycled, the ultimate disposal of these vehicles is going to fall onto society and the taxpayer. We as a society shouldn't be subsidizing auto manufacturers' marketing ploys and we shouldn't let ourselves be deceived by them either.
