Studies have been conducted in France and Spain for (1) the validation of sampling methods to achieve representative samples of end‐of‐life tyre (ELT) materials and (2) the comparison and validation of test methods to quantify their biomass content. Both studies conclude that the 14C techniques are the most reliable techniques for determining the biomass content of end‐of‐life tyres. Indeed, thermogravimetry and pyrolysis‐GC/MS do not lead to results consistent with the theoretical content of biogenic materials present in tyres, and results in both cases differ considerably from the known natural rubber content of the reference samples studied using thermogravimetric analysis. Furthermore, in the two last techniques, natural isoprene cannot be distinguished from synthetic isoprene. Results obtained with radiocarbon analysis based on 14C contents could be used as reference values of the biomass content of the ELTs: in the ranges of 18–22% for passenger car tyres and 29–34% for truck tyres, in line with actual natural rubber and other components content. Additionally, the presence of textile fibres and stearic acid, which are known sources of biomass in the tyre, cannot be evaluated by thermogravimetry and pyrolysis‐GC/MS techniques.
Part of the book: Biomass Volume Estimation and Valorization for Energy