The growing demand for greener transport along with progress in vehicle electrification has led to an increased focus on accurate Emission Factors (EFs) for non-exhaust sources like tyres. Tyre wear arises through mechanical and thermal processes, generating Tyre Road Wear Particles (TRWP) composed of rubber polymers, fillers, and road particles. This research aims to establish precise tyre airborne EFs for real-world conditions, emphasizing in an efficient collection system to generate accurate PM10 and PM2.5 EFs from passenger car tyres.
Particle generation replicates typical driving on asphalt road for a wide selection of tyres (different manufacturers, price ranges, fuel economy rating). Factors such as tyre load, speed and vehicle acceleration are also considered to cover various driving characteristics. The collection phase focuses on separating tyre wear particles from potential contaminants, such as brake particles and other road particles, while maintaining high capture efficiency. To achieve this, the collection system is designed and optimized using Computational Fluid Dynamics (CFD) simulations to define the exact positioning, geometry and flow characteristics of the sampling nozzle, maximize particle capture and limit any loss for particles ranging in diameter from 10 nm to 10 μm. An advanced setup, incorporating a full-enclosure around the brake system and cleaning of a closed, controlled test track, is used to further prevent cross-contamination from other particle sources. Advanced instrumentation is used to characterize the collected particles, employing Electrical Low-Pressure Impactors (ELPI) for particle number and size distribution, and gravimetric method and subsequent analyses (ICP-MS, GC-MS, and pyrolysis GC/MS) to quantify metal, organic components, distinguish TRWP from other sources and calculate the PM10 and PM2.5 EFs.
Despite limitations in fully replicating real-world conditions and eliminating contaminants, this work fills critical data gaps, supporting future regulations and more accurate emission inventories representing real-world driving conditions.