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Renewable diesel fuels have the potential to reduce net CO2 emissions, and simultaneously decrease particulate matter (PM) emissions. This study characterized engine-out PM emissions and PM-induced reactive oxygen species (ROS) formation potential. Emissions from a modern heavy-duty diesel engine without external aftertreatment devices, and fueled with petroleum diesel, hydrotreated vegetable oil (HVO) or rapeseed methyl ester (RME) biodiesel were studied. Exhaust gas recirculation (EGR) allowed us to probe the effect of air intake O2 concentration, and thereby combustion temperature, on emissions and ROS formation potential. An increasing level of EGR (decreasing O2 concentration) resulted in a general increase of equivalent black carbon (eBC) emissions and decrease of NOx emissions. At a medium level of EGR (13% intake O2), eBC emissions were reduced for HVO and RME by 30 and 54% respectively compared to petroleum diesel. In general, substantially lower emissions of polycyclic aromatic hydrocarbons (PAHs), including nitro and oxy-PAHs, were observed for RME compared to both HVO and diesel. At low-temperature combustion (LTC, O2 < 10%), CO and hydrocarbon gas emissions increased and an increased fraction of refractory organic carbon and PAHs were found in the particle phase. These altered soot properties have implications for the design of aftertreatment systems and diesel PM measurements with optical techniques. The ROS formation potential per mass of particles increased with increasing engine O2 concentration intake. We hypothesize that this is because soot surface properties evolve with the combustion temperature and become more active as the soot matures into refractory BC, and secondly as the soot surface becomes altered by surface oxidation. At 13% intake O2, the ROS-producing ability was high and of similar magnitude per mass for all fuels. When normalizing by energy output, the lowered emissions for the renewable fuels led to a reduced ROS formation potential.

Toxicity of engine out emissions from primary and secondary aerosols has been a major cause of concern for human health and environmental impact. This study aims to evaluate comparative toxicity of nanoparticles emitted from a modern common rail direct injection engine (CRDI) fuelled with biodiesel blend (B20) vis-à-vis mineral diesel. The toxicity and potential health hazards of exhaust particles were assessed using various parameters such as nanoparticle size and number distribution, surface area distribution, elemental and organic carbon content and polycyclic aromatic hydrocarbons adsorbed onto the particle surfaces, followed by toxic equivalent factor assessment. It was found that biodiesel particulate toxicity was considerably lower in comparison to mineral diesel.

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Background: Diesel exhaust is carcinogenic and exposure to diesel particles cause health effects. We investigated the toxicity of diesel exhaust particles designed to have varying physicochemical properties in order to attribute health effects to specific particle characteristics. Particles from three fuel types were compared at 13% engine intake O 2 concentration: MK1 ultra low sulfur diesel (DEP13) and the two renewable diesel fuels hydrotreated vegetable oil (HVO13) and rapeseed methyl ester (RME13). Additionally, diesel particles from MK1 ultra low sulfur diesel were generated at 9.7% (DEP9.7) and 17% (DEP17) intake O 2 concentration. We evaluated physicochemical properties and histopathological, inflammatory and genotoxic responses on day 1, 28, and 90 after single intratracheal instillation in mice compared to reference diesel particles and carbon black.

A comparative morphological analysis was performed on the exhaust particles emitted from a common rail direct injection (CRDI) sports utility vehicle (SUV) engine for primary and aged particulates. In this study, soot particles were collected from the CRDI engine fuelled with mineral diesel and 20% biodiesel blend (B20). The engine was operated at a constant speed of 1800 rpm for five different loads (0%, 25%, 50%, 75%, 100% rated load) for primary and aged particulate collection. Primary particulate samples were collected on pre-conditioned quartz filter papers from the exhaust stream after partial dilution. For collection of aged particles, the diluted exhaust was passed through a customized photochemical chamber with 2 hour retention time. This allowed photochemical reactions to proceed in presence of ultraviolet light leading to particulate aging in simulated daylight conditions and particulates were collected downstream of the photochemical chamber. Particulate laden filters were observed by scanning electron microscopy (SEM). It was observed that B20 emitted significantly lower primary particulates in comparison to mineral diesel for all the loads. B20 emitted lower particulates at lower load conditions for aged samples. At higher engine loads (75% and 100%), this reduction in aged particulates for B20 compared to mineral diesel was quite significant.

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