Comparative Life Cycle Assessment of Hardmetal Chemical Recycling Routes

Secondary hardmetal is a large part of the supply for new hardmetal products, yet the environmental impacts of hardmetal recycling remain unknown to a large degree. The goal of this study was to evaluate the gate-to-gate impacts of tungsten and cobalt recovery by chemical recycling. The LCI data was obtained from process simulations and the environmental impact categories were calculated using GaBi software. The simulations were used to study process performance and to investigate the effect of process parameter variation on the environmental impact indicators. Compared to primary production, chemical recycling decreased impacts by more than 50% in all investigated impact categories. The global warming potential for treating 1 metric ton of hardmetal scrap by standard chemical recycling to APT and Co(OH)2 was 6121 kg CO2-eq., freshwater consumption 142 m3, eutrophication potential 2.3 kg P-eq., ozone depletion potential 0.0030 kg CFC-11-eq., acidification potential 91 kg SO2-eq., and photochemical ozone formation potential 11 kg NOx-eq. Process hotspots depended on the impact category of interest, but in most cases included oxidation of the scrap material and APT production. Major contributors to environmental impacts included electricity consumption, leaching chemicals, and heating required by the oxidation.