Dissipation of tungsten and environmental release of nanoparticles from tire studs: A Swedish case study
Journal article, 2019
Tire studs, with pins made of cemented tungsten carbide with cobalt (WC-Co), are used in many countries during winter. Tungsten, the main content of the pins, is geochemically scarce and a critical raw material. In addition, analytical studies have identified WC-Co nanoparticles in the environment, which are worn off during the use of studded tires. The aims of this study are to assess (i) the dissipation rate and functional recycling related to the use of tungsten in tire studs as well as (ii) the magnitude of the WC-Co nanoparticle release in Sweden. Tungsten mass flows related to WC-Co in tire studs were estimated throughout the product chain, from mining to waste management, using material flow analysis. This study shows that 100% of the tungsten in Swedish tire studs is presently dissipated (67% as release during use) and there is no functional recycling. This can be compared with the estimated average global dissipation rate of >60% and functional recycling rate of 10-25% after use for tungsten. Recovery of tungsten during waste management and alternative solutions to WC-Co in tire studs are discussed as possible remedies. Furthermore, the estimated release of nano-sized WC-Co particles is in the same order of magnitude as the modeled release of some engineered nanomaterials in Sweden and higher than for e.g. nano-silver.
Material flow analysis