Once a vehicle has had valuable parts removed, along with any pollutants such as the oil, fuel and battery, it is ready to be crushed, baled and shredded. But that is by no means the end of the process for recovery.
Thanks to a variety of processes – including magnetic, sink/float, air separation and induction/ X-ray – metals and plastics are also saved from landfill to be recycled or reused.
An issue has always been what to do with all that is left behind after all of the above have been carried out. Despite containing several types of potentially valuable materials, such as plastic (about 45%), textiles (29%) and foam (13%), as well as smaller quantities of rubber, ferrous metals, aluminium, copper and paper, it has not been possible to separate and recover this automotive shredder residue (ASR) cost effectively, so instead it has all gone to landfill.
The challenge faced by those looking to process ASR is that it has already been through a comprehensive series of sorting procedures to extract as much material as possible. What remains is largely the result of inefficiencies in those methods.
“Few, if any, suppliers offer technology that can process asr sufficiently well to extract the variety of resources present.”
But there is value in going the extra mile to recover more resources, for sustainability purposes as well as economic ones.
Extra wet screening and sorting will be of most benefit to the largest ASR recyclers. The volumes they process and the high degree of automation in their plants mean that processing material below 20mm becomes worthwhile. It can bring in added value rather than being a cost.
The early stages of ASR processing usually involve using a trommel or flip-flow screen to extract the main constituents at less than 15 or 20mm, including sand, glass and mineral (40%), plastics (25%), organics (20%) and metals (15%).
The remaining metals are often the next focus; some are removed using basic dry screening, magnets, eddy current separator (ECS) and perhaps density separation, wind sifting or air knife.
Finally, the remaining material is washed and screened to produce further sand and aggregates that meet legislation for secondary aggregates reuse. The materials that are recovered can be suitable for a range of applications, including embankments, fill materials, capping and sub-base for paving areas.
automotive shredder residue
At this stage, plastics that may be suitable for further processing or incineration can also be recovered. Much of any remaining ferrous and non-ferrous metals can also be recovered at this stage.
Few, if any, suppliers offer technology that can process ASR sufficiently well to extract the variety of resources present. Instead, plants dealing with ASR tend to rely on a number of suppliers and form modular solutions.
To extract full value, an ASR plant may require a shredder, finger and flip-flow screens, wind sifting, air knife, wet sink/float system, magnet ECS steps, in-duction and X-ray separation technology, milling and density separation.
This is not something that can be done on a small scale. A sophisticated plant averages operating costs of around £500,000 per process tonne per hour, meaning that a 20-tonne tonne/hour plant may require a £9m+ investment.
If we are to truly achieve a circular economy, which keeps resources in the loop, every aspect of material recovery needs to be implemented. CDEnviro is proud to be playing its part in this recovery challenge, making sure that sifting through scrap is worthwhile and the remaining resources are saved from landfill.
We know the challenge is far from over. In future, ASR will no longer be the biggest problem in automotive recycling. With more and more cars being made as composites – so that they are lighter and consume less fuel – there will be new challenges for those looking to recycle them. We will be looking to play our part in those solutions too.
Sean Dobbs is senior product development engineer at waste management specialist CDEnviro