Can torrefaction be a suitable method of enhancing shredder fines recycling?

Effective recycling of metallic waste and end-of-life vehicles (ELVs) is of crucial importance. Currently used separation and sorting techniques result in the formation of fine residue (usually below 10-20 mm) called shredder fines. Shredder fines contain the so-called 'fluff' (i.e., foam, wood and textile fibres) with metal particles entangled in it. This 'fluff' interferes with sorting techniques and thus reduces the metal recycling rate. For this reason, presently, shredder fines are primarily landfilled, which is not covered by the greater objective of the circular economy; therefore, the need for their recycling emerged. Low-temperature pyrolysis (torrefaction) increases the 'fluff' fragility and thus liberates the metal particles without their substantial oxidation, thereby enabling their recycling. For that reason, in this article, shredder fines torrefaction was performed at the temperature range of 250-450 °C. The process products were comprehensively characterised using, among others, MicroGC (non-condensables), GC/MS (condensables), and ICP-SFMS (char). The possible application of the torrefied shredder fines after the metal sorting was discussed as well. Torrefaction was identified as a promising way of shredder fines recycling, and the torrefied shredder fines after metals sorting have the potential to be used as an ingredient of a raw material mix for cement kilns.