The primary factor in the formation of polycyclic aromatic hydrocarbons (PAHs) in diesel engines, which pose environmental and health risks, is the chemical composition of the diesel fuel. Higher-carbon alcohols have emerged as promising oxygenated blending components for compression ignition engines due to their potential to improve combustion and reduce harmful emissions. However, limited data exist regarding their impact on PAH formation and toxicity characteristics. This study investigates the effects of 15% (v/v) n-propanol, n-butanol, and n-pentanol blends with petroleum diesel (D) and waste cooking oil biodiesel (B) on total PAH emissions, PAH dispersion, and toxicity in a diesel engine under steady-state conditions. Total PAH concentrations and individual species distributions were quantified, and toxicity was evaluated using toxicity equivalency factor (TEF) methodology. Results indicate that the addition of higher alcohols significantly reduces total PAH emissions compared to the respective base fuels. A marked decrease in high-molecular-weight (4–6 ring) PAH compounds was observed, suggesting suppression of heavy PAH formation pathways. Toxicity-weighted PAH emissions also decreased with alcohol blending. Furthermore, total PAH concentrations for all tested blends remained below the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL = 0.2 mg/m3) under the examined operating conditions. These findings demonstrate that 15% higher alcohol blends are effective in mitigating PAH emissions without adverse environmental health implications.
Atmanlı et al. (2026) studied this question.