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Title of the thesis: Environmental impacts of processing secondary cobalt raw materials

Thesis defender: Riina Aromaa-Stubb
Opponent: Prof. Johan Berg Pettersen, Norwegian University of Science and Technology, Norway
Custos: Prof. Mari Lundström, Aalto University School of Chemical Engineering

The move from fossil fuels to greener technologies increases the need and demand for many metals. One of these is cobalt which is used in lithium-ion batteries, but also in more traditional applications such as hardmetal and catalysts. Currently cobalt is produced nearly entirely from primary resources and production is highly concentrated geographically. The primary production of cobalt has also been associated with environmental concerns. Increasing the supply of cobalt from secondary raw materials has been considered an option to decrease environmental impacts and help diversify the supply. However, also secondary production of cobalt has environmental impacts, and the aim of this thesis was to study the impacts associated with cobalt recycling from hardmetal and cobalt catalysts.

The environmental impacts were studied by using simulation-based life cycle assessment (LCA) in which the studies processes were simulated based on process data from literature. The methodology allows for investigation of also processes still in the development stage since the process simulation can be used to build an inventory that described both the direct emissions of the process as well as the consumption of used chemicals and utilities. The thesis studied both industrially used processes and processes still in development. In nearly all scenarios the environmental impacts of the recycling processes were smaller than those of equivalent primary production which encourages increasing the use of recycled cobalt in the production of new cobalt products.

The data produced by process simulation is considered secondary data in LCA, meaning that there is a higher uncertainty associated with it compared to primary data on mass and energy balances measured directly from a plant. The thesis studied therefore also how different sensitivity and uncertainty analyses affect how the uncertainty in the simulated data shows up in the conclusions and recommendations made based on the LCA results. For the most part, the difference between the analysis methods was small. However, particularly related to the direct emissions, not including the uncertainty related to process simulation parameters underestimated the effect the uncertainty had on the results.

Keywords: process simulation, environmental impacts, hardmetal recycling, catalyst recycling

Thesis available for public display 7 days prior to the defence at . 

Contact information: 
riina.aromaa-stubb@aalto.fi