Fig. 4: Normalization of midpoint results, via the IMPACT WORLD+ v.1.29 method, as percentage change from the value obtained with the global nickel sulfate dataset in ecoinvent, for 1 kg Ni_eq.

The six modelled concentrate processing routes are assessed over all midpoint categories to explore any burden shifting risks from prioritizing sourcing via one pathway versus another and to identify life cycle assessment implications of using one particular dataset versus the existing global ecoinvent dataset. To note here that the smelting and refining dataset for nickel sulfide concentrate in ecoinvent was selected in lieu of the flash smelting dataset, due to its better coverage of emissions to air and water. For midpoint results with percentages of change exceeding 100%, the corresponding value is noted directly on the associated bar. Abbreviations: GWP-l: Climate change, long term (kgCO_2eq), GWP-s: Climate change, short term (kgCO_2eq), FNEU: Fossil and nuclear energy use (MJ deprived), FAP: Freshwater acidification (kgSO_2eq), FETP: Freshwater ecotoxicity (CTUe), FEP: Freshwater eutrophication (kgPO₄, P-lim_eq), HTP-c: Human toxicity cancer (CTUh), HTP-nc: Human toxicity non cancer (CTUh), IR: Ionizing radiations (Bq C-14_eq), LU-o: Land occupation, biodiversity (m² arable land eq .yr), LU-t: Land transformation, biodiversity (m² arable land_eq), MEP: Marine eutrophication (kg N, N-lim_eq), MRU: Mineral resources use (kg deprived), ODP: Ozone Layer Depletion (kg CFC-11_eq), PMF: Particulate matter formation (kg PM2.5_eq), POF: Photochemical oxidant formation (kg NMVOC_eq), TAP: Terrestrial acidification (kg SO_2eq), WU: Water scarcity (m³ world_eq).