Environmental impact of pyrolysis of mixed WEEE plastics part 2: Life cycle assessment.

Waste electrical and electronic equipment (WEEE) contains up to 25% plastics. Extraction of higher quality fractions for recycling leaves a mix of plastic types contaminated with other materials, requiring the least environmentally harmful disposal route. Data from trials of pyrolysis, described in part 1 of this paper set, were used in a life cycle assessment of the treatment of WEEE plastics. Various levels of recycling of the sorted fraction were considered, and pyrolysis was compared with incineration (with energy recovery) and landfill for disposal of the remainder. Increased recycling gave reduced environmental impact in almost all categories considered, although inefficient recycling decreased that benefit. Significant differences between pyrolysis, incineration and landfill were seen in climate change impacts, carbon sent to landfill, resources saved, and radiation. There was no overall "best" option. Landfill had the least short-term impact on climate change so could be a temporary means of sequestering carbon. Incineration left almost no carbon to landfill, but produced the most greenhouse gases. Pyrolysis or incineration saved most resources, with the balance depending on the source of electricity replaced by incineration. Pyrolysis emerged as a strong compromise candidate since the gases and oils produced could be used as fuels and so provided significant resource saving without high impact on climate change or landfill space.