Life cycle greenhouse gas emissions of titanium and zirconium recovery from oil sands tailings

Tailings generated during the extraction of oil sands bitumen contain significant amounts of zirconium and titanium. These untapped resources are stockpiled in tailings ponds. Various processes to recover titanium and zirconium from tailings have been proposed; however, there is limited information on the associated greenhouse gas emissions. In this study, the life cycle GHG emissions of titanium and zirconium recovered from bitumen extraction tailings were assessed. The life cycle stages include oil sands mining and bitumen extraction, as the source of tailings enabling mineral recovery, and mineral concentration and separation processes. Upstream emissions associated with producing consumables and electricity along with the production and combustion of natural gas to provide heat to the process were considered. Emissions avoided by diverting residual diluent from tailings ponds and recovering residual bitumen from the processed tailings were also accounted for. The estimated GHG emissions from mining and bitumen extraction, including reduced emissions from tailing ponds, are 579 kg CO 2 eq/m 3 of produced bitumen, while those associated with mineral recovery are 652 kg CO 2 eq/t of heavy minerals recovered. Different methods to distribute those emissions among the products were explored. Uncertainty analysis was conducted to understand the effect of randomness in the input parameters. About 90 % of the estimates lie between 543.5 and 673.1 kg CO 2 eq/t, before any attribution of GHG emissions. Sensitivity analysis shows that the emission factors associated with natural gas combustion, electricity production, and diluent production have the greatest effect on the estimates.