Public defence, Processing of Materials, MSc (Tech.) Heikki Lappalainen

Title of the thesis: Life cycle assessment of lithium processing from hard rock and spent battery materials

Thesis defender: Heikki Lappalainen 
Opponent: Assistant professor Robert Istrate, Institute of Environnemental Sciences (CML) – Leiden University, the Netherlands
Custos: Prof. Mari Lundström, Aalto University School of Chemical Engineering

Life cycle assessment of lithium processing from hard-rock and spent battery materials

The rising demand for lithium due to its use in lithium-ion batteries requires increased lithium production from primary sources, such as brines and hard-rocks, as well as from battery recycling. The environmental impacts of different production routes must be evaluated and optimized to mitigate the environmental impacts associated with the green transition. This thesis focuses on evaluating the environmental impacts of primary lithium production from spodumene ore concentrate, as well as from secondary battery recycling. Process simulation-based life cycle assessment is applied to quantify the environmental impacts of different hydrometallurgical processing scenarios.

The results show that the environmental impacts of primary lithium production from spodumene through the recently developed soda leaching process are generally lower than those of the conventional sulfuric acid roasting process. This applies to both target products: lithium hydroxide monohydrate and lithium carbonate. Furthermore, comparison between the two products suggests that the impacts attributed to lithium carbonate are higher than those associated with lithium hydroxide. If lithium carbonate produced through either route – soda leaching or sulfuric acid roasting – is further converted to lithium hydroxide, the environmental impacts of the carbonate routes are further increased in comparison with direct lithium hydroxide production. Of all the primary production scenarios studied, soda leaching with lithium hydroxide as the product shows the lowest environmental impacts. In all processing routes, energy-related streams, such as steam and electricity, generally have a high contribution to most impact categories. Upstream production of chemicals, such as sulfuric acid, soda ash, sodium hydroxide and quicklime, are also among the significant sources of impacts. Lithium produced from battery recycling has a lower environmental burden than production from primary sources.

Process modelling has been suggested as the recommended way to acquire secondary data for life cycle assessments (LCAs) if no primary plant data is available. Nevertheless, some uncertainty is inherent in the methodology as the data obtained from process simulations is limited by the quality of the models. This underlying uncertainty was investigated through sensitivity analyses and further by constructing simplistic process models. The results are partially ambiguous, and do not provide decisive conclusions. Instead, this highlights the need for careful estimation of the reliability of process model-based LCAs, e.g. through comprehensive sensitivity analysis. Nevertheless, process simulation-based LCA was found to provide valuable data for the evaluation of environmental impacts of different process scenarios, especially when they are not too similar to each other.

Keywords: lithium, environmental impacts, life cycle assessment, process modelling, spodumene processing, battery recycling

Thesis available for public display 7 days prior to the defence at Aalto University's public display page.

Contact information: 
heikki.2.lappalainen@aalto.fi 
www.linkedin.com/in/heikki-lappalainen