Prospective life cycle assessment of hydrometallurgical cobalt processes for the battery value chain

The environmental impact of electrification has been debated due to the considerable increase in consumption of metals such as cobalt, nickel, manganese, and lithium. Although cobalt can be partly substituted in electric vehicle batteries with metals such as nickel, it remains a critical metal for energy transition and its demand is projected to increase. The sustainable supply of cobalt is dependent on the diversification of sources, including both mining and recycling. The goal of this study was to assess the impacts of emerging primary cobalt and lithium-ion battery recycling processes using a simulation-based life cycle assessment approach, which enables the modeling of prospective scenarios in high detail.  In this thesis, life cycle inventory data was obtained by simulating the selected flowsheets with HSC Sim software, and the impacts were calculated using GaBi. Scenario, contribution, and sensitivity analyses were used to aid interpretation of the results. Overall, six primary cobalt and four lithium-ion battery recycling scenarios were simulated based on several preliminary simulations that were used to guide flowsheet development. To be potentially industrially relevant, all scenarios utilize hydrometallurgical processing in sulfuric acid solutions.  According to the results, higher grade feeds result in lower impacts during hydrometallurgical processing, and optimizing the leaching conditions may effectively decrease the impacts. Although maximizing cobalt recovery is recommended for primary cobalt, it was observed for lithium-ion battery recycling processes that some valuable losses may be justifiable if this means that milder conditions can be applied. The results also suggest that solvent extraction chemicals may contribute more significantly to the environmental impacts than previously thought, and there is a critical need for primary life cycle inventory data from extractant manufacturers.  Simulation-based life cycle assessment was used to assess the impacts of the hydrometallurgical processing of cobalt-bearing raw materials in this research, but it is a suitable method for the evaluation of a wider array of raw materials and processes. The strength of the methodology lies in the ability to create high resolution inventories from limited experimental or literature data. However, it requires both metallurgical and life cycle assessment expertise to correctly justify assumptions and interpret the results for informed decision-making. This thesis presents the effect of some of the assumptions and process parameters in the impacts of hydrometallurgical processing and suggests improvements to further develop the studied processes.