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The general aim of this study is the recovery of Automotive Shredder Residue (ASR). The ASR light fraction, or car fluff, that was collected at an Italian shredding plant was pyrolysed at various temperatures (500–800 °C) in a lab-scale reactor. The condensable gases (tar) and solid residue yields increased with decreasing temperature, and these products were characterized to suggest a potential use to reclaim them. The higher heating value (HHV) of tar was 34–37 MJ/kg, which is comparable with those of fossil fuels. Furthermore, the ash content was low (0.06–4.98%). Thus, tar can be used as an alternative fuel. With this prospect, the concentrations of polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in tar were determined. The toxicity of tar changes with temperature (1–5 ng I-TEQ/g), and the PCDFs significantly contribute to tar toxicity, which was 75–100% with a maximum of 99.6% at 700 °C. Regarding the characterization of the solid residue, the low HHV (2.4–3.3 MJ/kg) does not make it suitable for energy recovery. Regarding material recovery, we considered its use as a filler in construction materials or a secondary source for metals. It shows a high metal concentration (280,000–395,000 mg/kg), which is similar at different pyrolysis temperatures. At 500 °C, polycyclic aromatic hydrocarbons (PAHs) were not detected in the solid residue, whereas the maximum total PAH concentration (19.41 ng/g, 700 °C) was lower than that in fly ash from MSWI. In conclusion, 500 °C is a suitable pyrolysis temperature to obtain valuable tar and solid residue.

We developed a phenomenological approach to explain the kinetic experimental data of PCDD/F formation/destruction based on a reaction mechanism model at the congener group level. In the present work, we investigated the formation and destruction of PCDD/F on fly ash as a function of time at 280 °C, chlorine mass balance, evolution of the total equivalent toxicity and kinetic modelling. We determined that the volatilization process is negligible and that the reactive processes at short reaction times only become important above 300 °C. The results provide a substantial improvement on existing studies. We experimentally demonstrated, for the first time, that there is a correlation between the oxidative breakdown of native carbon and PCDD/F de novo synthesis. Data processing by our kinetic model showed that the formation of oxygen complexes C(O) was the determining step for de novo synthesis of PCDD/F. Indeed, the calculated reaction time at which the PCDD/F concentration was at a maximum (850 min) was greater than that calculated for the oxygen complexes C(O) (435 min). Moreover, the experimental carbon conversion efficiency for PCDD/F production (0.0032% at 600 min maximum) was in a very good agreement with the theoretical conversion (0.0041%).

In the recent past we reported the investigation of different devulcanization processes of a ground tire rubber (GTR) such as supercritical fluid, ultrasonic and biological technologies. Each of these techniques had been previously optimized, focusing on the experimental combination of parameters providing the best devulcanization conditions. The present study aims to extensively compare the optimal conditions of these three different techniques for the devulcanization of a GTR. In particular the GTR and the devulcanizates by each technique were blended into raw natural rubber at a concentration of 10 phr. The rheological and mechanical properties of their vulcanizates were investigated and compared to find out the rubber providing the highest compatibility for compounding and revulcanization. In addition, a comparison of these results was made with the ones of raw natural rubber compound and vulcanizate.