Reducing carbon-dioxide emission (CO 2) is one of the most important challenges of today to overcome. A major source of CO 2-emission comes from the usage of internal combustion engines in vehicles to transport people and goods. This emission is directly proportional to fuel consumption. In order to reduce CO 2-emissions, European Union legislations state that by 2015, the fleet averaged CO 2-emissions from a passenger car manufacturer is limited to 130g/ km. Reaching 2020 the limitations are even tougher, a fleet average of only 95g/km is allowed. If a manufacturer fails to meet these requirements, the manufacturer has to pay "excess emissions premiums" for every car registered, basically a penalty-tax if the requirements are not fulfilled. Fuel consumption is even more important for engines used in heavy trucks. These vehicles travel longer annual distances, making fuel cost a significantly larger part of total costs compared to a passenger car. Hence, improvements in fuel economy are highly desired. Improving engine brake efficiency is vital in order to achieve these requirements. Brake efficiency (η b), is the function of four parts: combustion (η c), thermodynamic (η t), gas-exchange (η ge) and mechanical (η m). All of these efficiencies need to be high in order to reach high brake efficiency. Definitions of these efficiencies are presented in Figure 1. Further information and definitions of the variables used in Figure 1 are presented in appendix A.

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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.

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.

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