Reducing the chemical risks associated with treating automotive shredder residue

Outline of reasons and objectives
Initially entitled “reducing the risks induced by shredding”, this study proposed to address that operation through three focuses: developing a ventilation solution suitable for channelling the flows of dust in a rotary shredder by using the centrifugal force; studying the shredding parameters suitable for limiting the emission of pollutants during treatment of fluorescent tubes and bulbs; and assessing the emissions during treatment of automotive shredder residue. Since the third focus is the only one that was addressed in this study, it was renamed “chemical risk associated with treating automotive shredder residue”.
European Directive 2000/53/EC aims to achieve a rate of recycling and reuse of End-of-Life Vehicles (ELVs) of 95%. Most ELVs are treated in automotive shredders, and are mixed with other flows of waste such as those coming from waste electrical and electronic equipment (WEEE). However recycling the residues resulting from the shredding still needs to be optimised. This work aimed to study the risks associated with the development of a new process for treating automotive shredder residue (ASR) under a project funded by the French National Research Agency (ANR).
Approach
The REFORBA (Recycling of the Organic Fraction of Automotive Shredder Residue) Project involves five partners comprising two other research institutes, an ELV recycler, a steelmaker, and INRS in order to develop a process for treating ASR making it possible to improve recycling of the light fraction or plastic fraction and the mineral fraction that is more rich in iron oxide. INRS’s participation was aimed at taking prevention aspects into account as of the process design phase.
Each operation making up the process was assessed after having first characterised the various flows to be recycled.
Main results
Apart from a prior sieving stage, the technological choice of liquid treatment for the plastic fractions made it possible to eliminate all of the sources of emission of dust that can contain toxic metal species or whose toxicity can be increased by the presence of wood dust.
The mineral fraction was treated during various stages in order to enrich it with iron oxide with the aim of reinjecting it into blast furnaces. The separation operations that were involved (screening, sieving, and magnetic separation) can all emit toxic dust, in particular dust having a high lead content. In order to limit dissemination of such dust around the workplace, it is necessary to keep the fractions at a high level of humidity within the limits of the operating conditions for the process.
Discussion
Initially intended to cover a broader spectrum, by looking at the consequences of shredding operations in general, the study had its original ambitions reduced. It re-focused essentially on participating in the REFORBA project, centred on preventing the risks associated with the separation techniques implemented during treatment of ASR. The assessment made of them makes it possible to enrich the assessment of the risks in the companies who will implement the imagined process, so that they can anticipate them.