Is the assimilation to a solid recovered fuel a viable solution for automobile shredder residues' management?

Abstract

Directive 2000/53/EC and the European Circular Economy Package (2018) required the Member States to take all the necessary measures to reach the reuse-recycling goal of 85% for end-of-life vehicles (ELVs). In 2019, Europe achieved 89.6% of reuse-recycling, but most EC countries are still not completely compliant, Italy standing, for example, at only 84.2%. For this reason, actions are necessary to increase reuse-recycling for the waste generated in the operations of ELV shredding and separation, known as automobile shredded residues (ASRs). This study was aimed at assessing if the assimilation of ASRs to a solid recovered fuel (SRF) was a feasible solution. That would allow the waste to lose its status (end-of-waste, EoW), thus increasing the recycling rate. The assimilation of ASRs to SRFs requires the compliance with a series of parameters, namely net calorific value (NCV), content of chlorine (Cl), mercury (Hg) and selected heavy metals. The above-mentioned parameters were analyzed in the principal ASR fractions, namely textile, plastic and foam rubber, found in the samples collected during four sampling campaigns (2017-2021) performed at the same ELV treatment plant. Notwithstanding the great variability observed in the four samples, the results of the analyses revealed that the three fractions were compliant with NCV, Cl and Hg content. Conversely, the heavy metals' content was found a more critical parameter, in fact only the plastic fraction was suitable for SRF assimilation. Textiles presented criticality for the content of copper (Cu), nickel (Ni) and antimony (Sb). The heavy metals' contamination of foam rubber was found to be strongly related to particles' dimensions. A model which put particle size and metals' content into relationship was developed and validated. Removing particles of <40 mm significantly improved the quality of the material, however the content of Cu and Ni remained a critical issue for particles up to 200 mm. The SRF assimilation of the plastic fraction would increase the reuse-recycling rate of approx. 2.4-3.3%, thus allowing the achievement of the EC goals concerning the ELV management.

Keywords: End-of-life vehicles; End-of-waste; Heavy metals; Thermal valorization; Waste characterization.