A Circular Approach for Recovery and Recycling of Automobile Shredder Residues (ASRs): Material and Thermal Valorization

Abstract

The transition of the automotive industry towards a circular economy requires viable solutions for end-of-life vehicle (ELV) reuse, recycling and recovery. This study tested the feasibility of two recycling processes intended, the first, to produce recycled plastic composite goods from selected plastic fractions extracted from ASRs, through a conventional mechanical process; the second, to use the remaining ASRs as a solid recovered fuel (SRF) to saturate the residual treatment capacity of the local (Turin, NW Italy) municipal solid waste (MSW) incineration plant. Samples of light (CER code 191004) and heavy (CER code 191204) ASRs were collected from an ELV authorized treatment facility, subjected to a complete characterization and tested for the two recycling options. The results demonstrated that selected fractions of thermoplastic polymers could be employed in a molding process for the production of recycled plastic composite goods. This fraction, equal to 2660 t/a, was more than 2% b.w. of the original ELV and 7.6% of the whole ASR waste product. The remaining ASR, after plastic extraction and recycling, had lower heating values (LHVs, 24 or 31 MJ/kg, depending on the original product) and chlorine content (< 50 mg/kg) that made it suitable to assume the status of SRF. In the present operating conditions, the Turin MSW incineration plant has a residual treatment capacity of at least 45,000 t/y, for waste with a LHV of 30 MJ/kg, that is approximately 30% more than the annual amount of ASRs produced in the Turin area. The application of mass and energy balances to the thermal process demonstrated that the addition of ASRs as an extra fuel to the incineration plant did not worse the quality of flue gases in terms of acid compound (HCl, SO2) concentration and allowed the annual net electrical energy production to be increased from 31 to 38 MW.