Environmental, Resource and Health Impacts of Hard Materials

Licentiate thesis, 2018

The importance of hard materials for society is illustrated by the fact that entire historical time periods have been named after the predominant hard material used at that time. In the latest century, the introduction of the hard material cemented tungsten carbide with cobalt (WC-Co) has contributed to the economic growth we have seen and this material is crucial for the manufacturing industry of today. At the same time, knowledge about its environmental, resource and net environmental impacts is limited and a number of important knowledge gaps exist. Chinese WC-Co production has been assessed in detail, but not production outside China. Resource impacts in terms of dissipation and recycling rates exist for tungsten in general but not for specific products containing tungsten. In addition, whether the use of WC-Co in products contribute to net improvements in environmental, resource and health impacts have not been assessed. This study applies the methods of life cycle assessment (LCA) and material flow analysis (MFA) in order to address these knowledge gaps. Environmental impacts of a typical non-Chinese WC-Co production have been assessed using LCA, while resource and net human health impacts are assessed for the WC-Co-containing product tire studs specifically using MFA and LCA, respectively. Results show that a few inputs and outputs dominate the life cycle environmental impacts of the non-Chinese WC-Co production and that recycling greatly reduces these impacts. The MFA study on tire studs showed that tungsten dissipation rate is notably higher than for the average tungsten product (98% vs >60%) and that the functional recycling of tire studs is effectively non-existent. Furthermore, results from the LCA study showed that the purpose of the tire studs to save lives and prevent injuries in traffic is not justified, since negative life cycle human health impacts (mainly from use phase emissions and occupational accidents in artisanal cobalt mining) outweigh the use phase-benefits of reduced accidents. A number of alternatives to WC-Co has been suggested in literature. However, the substitution potential varies due to often higher costs and reduced performance. Further research, applying a life cycle perspective, on the environmental, resource and human health impacts of such alternatives is recommended.