Particle-bound PAH emissions from a waste glycerine-derived fuel blend in a typical automotive diesel engine

Abstract

Polynuclear or polycyclic aromatic hydrocarbons (PAH) are known to be one of the most dangerous types of compounds of their class due to their carcinogenic potential. Some atmospheric PAH are measured and regulated to quantify the air quality. However, in order to better understand the presence of these compounds in the atmosphere it is crucial to study the PAH emissions sources. In this work, we analyze the particulate-bound PAH emissions, as well as their carcinogenic potential, from a typical baseline diesel engine using a promising alternative fuel obtained from the glycerol surplus in the biodiesel production industry. This advanced biofuel (Mo.bio) is a ternary mixture of residual glycerine-derived fuel (FAGE), a conventional fatty acid methyl ester (FAME) and a diesel fuel. Two operating conditions representative of the conflicting scenarios when studying polluting emissions (speeds of 50 km/h and 70 km/h typical of urban and extra-urban driving conditions) are used. In addition, with the purpose of deepening the understanding of the behavior of this new fuel, tests are carried out modifying the Exhaust Gas Recirculation (EGR) ratio. The PAH samples are collected before the aftertreatment systems in order to assess the possible formation of PAH with this type of fuel and to evaluate the options of the aftertreatment devices. Sampling is carried out using fiber-glass filters, extracting the trapped PAH using Soxhlet method. The analytical procedure (liquid chromatography with fluorescence detection) allows to appreciate differences between the different fuels and modes of operation, observing higher emissions of benzo[a]pyrene (BaP) and dibenz[a,h]anthracene (DahA) for the diesel fuel than for the mixture containing residual glycerine-derived fuel. Therefore, it is concluded that the fossil fuel has a larger carcinogenic potential in these conditions, and that the Mo.Bio fuel may possibly expand the EGR ratio range without increasing the requirement of the particle filter.