Pyrolysis of waste electrical and electronic equipment (WEEE) for recovering metals and energy: Previous achievements and current approaches

The amount of collected Waste Electrical and Electronic Equipment (WEEE) in Europe is growing about 7 wt.-% per year (2007-2012). It contains a number of economically relevant base, precious and high-tech metals. However, only a limited number of these metals can be recovered by currently applied recycling processes. Especially high-tech metals like gallium, germanium and tantalum get lost during the treatment of WEEE. The pyrolysis technology allows an accumulation of these metals from WEEEfractions without oxidation as well as the generation of high calorific gases and liquids for energetic utilization. This paper provides a literature based review of lab and medium-scale investigations on pyrolysis processes of different WEEE-fractions like printed wiring boards (PWB) or plastics to outline opportunities and challenges for recovering critical metals from WEEE via pyrolysis. The key procedural challenges are dehalogenation, avoidance of highly-toxic emissions (mainly PBDD/F) as well as preparation and accumulation of metals for recycling processes.