Auto manufacturer Mazda (Hiroshima / Japan; www.mazda.com) has developed what it claims to be a world-first recycling technology that enhances the process it uses to recycle used bumpers from end-of-life vehicles (ELV) into raw plastic resin for use in new bumpers. It is initially being used to make rear bumpers for the Mazda “Biante” minivan. The new technology is also claimed to be the first to enable recycling of used bumpers from different manufacturers at the same time. Additionally, by automating processes to remove metal attachments, it is claimed to significantly increase recycling efficiency.

Previously, unwanted materials such as metal attachments were removed by hand before the bumpers were visually inspected. Mazda overcame this labour-intensive process by developing technologies to automate the processes in collaboration with agricultural sorting machine developer Satake (Hiroshima / Japan; www.satake-group.com). Used bumpers are crushed into pellets and a machine similar to those used to separate contaminants from cereal grains removes unwanted metal pieces by shaking the pellets and directing airflow over them.

Mazda's new technology also resolves another limitation of previous methods. Depending on the vehicle manufacturer and age of the vehicle, used bumpers vary considerably in terms of the composition of polypropylene plastic and the paint's adhesive properties. While this has forced previous systems to treat different bumpers separately, Mazda's new technology successfully enables all bumpers to be recycled together.

The new process employs a kneading machine which is similar to those used for processing foodstuffs and chemicals including rubber and plastics. The machine applies a powerful shear force to the crushed bumper pellets, effectively stripping off the paint regardless of the plastic composition or paint properties, and without having to heat the plastic. Mazda now claims to separate crushed bumper pellets and achieve an average rate of paint removal of 99.85%. Crushed bumper pellets are subjected to a paint stripping process and collected in a hopper and passed through a shooter. As they exit the shooter, light is shone on them from various angles. Any paint adhered to the fragments reflects light more intensely than the (black) bumper material, this can be sensed in the machine and an air jet immediately removes the unwanted pellets.

Currently, around 20% of ELV (parts made of plastics, rubber and other materials) weight is incinerated as automobile shredder residue (ASR). Bumpers comprise a large proportion of the plastic so collecting and recycling ELV bumpers is expected to make a significant contribution to reducing ASR and optimising efficient use of resources. Mazda has developed and implemented efficient ELV bumper collection and processing methods in collaboration with auto parts specialist Yamako and plastics recycling company Takase Gosei Kagaku, both based in Hiroshima prefecture. As a result of these initiatives, the cost of recycling is less than the cost of purchasing new plastic, the company said.