Oral Presentation Society of Environmental Toxicology and Chemistry Australasia 2023

Understanding the chemicals in recycled rubber products from end-of-life tyres (#88)

Divina Navarro 1 , Anna Heitz 2 , Cynthia Joll 2 , Mike Williams 1 , Greg Davis 3 , Naomi J Boxall 3
  1. Environment, CSIRO, Waite, South Australia, Australia
  2. School of Molecular and Life Sciences, Curtin University , Bentley, WA, Australia
  3. Environment, CSIRO, Floreat, WA, Australia

Export of tyres is banned from Australia, creating pressure and opportunity for reuse and circular economy for rubber materials. Globally, chemicals found in tyres such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-quinone; 6PPD-Q) and hexa(methoxymethyl)-melamine (HMMM) have been identified as emerging chemicals of concern through growing ecotoxicological evidence, and this may impact potential reuse applications of recovered materials. However, the identification and assessment of hazards and risks related to the materials recovered from end-of-life (EOL) tyres on Australia’s unique environment and biodiversity are limited. Targeted analysis of a commercially available rubber product from recycled EOL tyres was undertaken to generate preliminary data related to the chemical composition of the product. Results indicated that the recycled rubber product was homogenous and contained many discrete organic and inorganic chemicals and mixtures. As expected, the sample preparation and extraction methods chosen for analysis likely influenced the type and concentration of chemicals detected and quantified in samples. Analytical results indicated that total recoverable hydrocarbons (TRH) could not be fully quantified or characterised by targeted analysis and that less targeted (or non-target) analysis of samples could provide better resolution of the chemical composition of the recycled rubber product as well as identify the unknown chemicals associated with these secondary materials. Sample representativeness was explored using metals as an indicator, and despite samples being classed as homogenous, individual metals, such as potassium and calcium, were variable. The individual variability of some metals indicated that increasing sample frequency and analysing replicate samples should be considered to minimise intrinsic sample variability and ensure the generation of high-quality data. Chemicals that occur in our broader waste streams should be better defined, and this study goes some way to building the foundational data required to support decision-making and enable resource recovery and circularity for rubber materials in Australia.