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The use of alternative fuels and among them the biofuels of 1st generation - fatty acid methyl esters FAME's and pure plants oils - for propulsion of IC engines is an important objective in several countries in order to save the fossil fuels and to limit the CO₂ production. The properties of bio-fuels and bio-blend-fuels can vary and this has an impact on the operation and emissions of diesel engines and on the modern exhaust aftertreatment systems. The present paper represents the most important results obtained with RME at AFHB, EMPA and EC-JRC. Most of the activities were performed in the network project BioExDi (Biofuels, Exhaust Systems Diesel) in collaboration between industry and research institutes.

All internal combustion piston engines emit solid nanoparticles. Some are soot particles resulting from incomplete combustion of fuels, or lube oil. Some particles are metal compounds, most probably metal oxides. A major source of metal compound particles is engine abrasion. The lube oil transports these abraded particles into the combustion zone. There they are partially vaporized and ultrafine oxide particles formed through nucleation [1]. Other sources are the metallic additives to the lube oil, metallic additives in the fuel, and debris from the catalytic coatings in the exhaust-gas emission control devices. The formation process results in extremely fine particles, typically smaller than 50 nm. Thus they intrude through the alveolar membranes directly into the human organism. The consequent health risk necessitates a careful investigation of these emissions and effective curtailment.

Particulate matter (PM) captured in diesel particulate filters (DPF) consists of: (a) soot, the product of incomplete combustion of the fuel and (b) ash, produced by combustion of lubricating oil plus minor amounts of metal components in the fuel. Among the various types of DPFs, most efficient are the so-called wall flow filters, where the exhaust gas is forced to pass through porous walls of adjacent channels, which are plugged alternately at their opposite ends. Accumulation of PM in DPFs leads to increasing pressure drop across the filter. Since increased PM load in the filter and thus increased pressure drop across the filter deteriorates the engine performance, the filter load of the DPF has to be periodically removed during a process referred to as regeneration. During the regeneration process, soot PM captured in the DPF is expected to be oxidized. The temperature needed for oxidation of PM is usually exceeding ca. 550°C.

Macroscopic studies and scanning electron microscope (SEM), as well as transmission electron microscope (TEM) research were carried out to investigate the nature and properties of particulate matter (PM) deposited in three diesel particulate filters (DPFs) operating with different fuels: 100% rapeseed methyl ester (RME100), a blend of 20% RME and 80% diesel (RME20), as well as 100% diesel (RME0). The DPFs were catalytically coated with V₂O₅/TiO₂. The PM deposits were either extracted from sectioned DPFs or studied "in situ," as deposited. In the RME100-DPF, the lowest soot and highest ash depositions are found. The higher amount of ash in RME100-DPF, as well as the higher participation of the element Ca in the ash from this filter, indicates that in addition to lubricating oil, the RME fuel contributes also to ash formation. Ash is found accumulating in the plugged inlet channels only in RME100 and as a few tens of μm-thick layer on the channel walls of all three filters.

Due to increasing concern about health effects of fine and ultra-fine particles (nanoparticles) from combustion engines, the diesel particle filter technology (DPF) *) was extensively introduced to heavy duty and passenger cars in the last years. In this respect, a very important parameter is the irreversible plugging of the DPF with non-combustible ashes. The quality of lubrication oil, especially the ash content has a certain influence on regeneration intervals of diesel particle filters. In the present study, the effects of different lubrication oils on particle mass and nano-particle size distribution were investigated. The test engine was a modern diesel engine without particle filter system. A main goal was to find out, how different lubrication oils influence the particulate emissions and the contribution of oil to total particle emissions. Moreover, first results of a tracing study will be discussed.