Understanding How Blending Different Ratios of Renewable Fuels with Diesel Impacts the Toxicity of Exhaust Particulates to Human Health

The urgent need to decarbonise transport has increased the utilisation of renewable fuels blended with current hydrocarbons. Heavy duty vehicle electrification solutions are yet to be realised and therefore the reliance on diesel engines may still be present for decades to come. Currently, the diesel supplied to fuel stations across the UK is a 7% blended biodiesel, whilst in South Korea a 5% blend is utilised. Biodiesel is produced from renewable sources, for example, crops, waste residue, oils and biomass. Particulates from diesel combustion are known to be toxic due to the presence of polycyclic aromatic hydrocarbons (PAHs), however there is very limited understanding of blending oxygenated fuels on the toxicity of the particulates produced. PAHs are aromatic structures that can be metabolised into chemicals which can disrupt DNA replication and potentially influence cancer mechanisms if inhaled in high quantities. Soyabean methyl-ester (SME) was blended at lower ratios, e.g., 5%, 10%, 15% and combusted in a light duty direct injection diesel engine to investigate and collect particulate emissions. Gas-Chromatography Mass-Spectroscopy (GC-MS) was used to characterise and identify PAH content of the collected particulate samples. Results showed that the lower blend fuels produced a greater amount of large ring PAHs, which correlated with a higher toxic effect in experiments undertaken using in-vitro cell models with collected soot samples. This toxic effect was of greater significance than that observed from combustion of either 100% fossil diesel (FD) or 100% SME biodiesel. The toxic effects found highlight the need to better understand impacts of renewable fuel utilisation on human health.