Effect of rapeseed methylester blending on diesel passenger car emissions – Part 1: Regulated pollutants, NO/NOx ratio and particulate emissions

• Tested Euro 4+ vehicles with 3 different exhaust aftertreatment systems.
• Different diesel–biodiesel blends used over 4 different driving modes.
• Limited increases observed in CO2 with the biofuel blends.
• Both NO and NO2 increased with the concentration of biofuel in the blend.
• Biodiesel decreased solid particles number and size in nonDPF equipped vehicle.

This paper summarizes the findings of an experimental study sponsored by the oil companies’ European association for environment, health and safety (CONCAWE) and performed by the Laboratory of Applied Thermodynamics of the Aristotle University (LAT/AUTh) which aimed to address the effect of rapeseed methylester (biodiesel) application on modern diesel passenger car fuel consumption and emissions. As more biodiesel enters the diesel pool, understanding the effects of higher concentration levels is increasingly important. The study was structured so that robust experimental data were generated. A hydrocarbon-only diesel fuel (B0) and three blends of rapeseed oil derived biodiesel at 10%, 30% and 50% v/v were tested. Three Euro 4+ compliant vehicles were used, one equipped with an oxidation catalyst while two others were equipped with different type of Diesel Particulate Filters. The test protocol included the EU certification cycle (NEDC), the more transient Artemis cycles and two steady state modes. Measurements included fuel consumption, regulated pollutants, NO/NOx ratio via fast NOx analyzer and particle number and characterisation. Systematic increases in fuel consumption with increasing biodiesel content were found but only limited differences in CO2 emissions (±2–3%). The presence of biodiesel increased CO emissions over cold start up to 200% and HC up to 170%. NOx emissions increased up to 20% with B50 in some cases with most differentiations lying in the 1–10% range depending on the blend and vehicle. NO emissions followed the same pattern. Biodiesel application led to decreases in PM emissions particularly for the nonDPF vehicle. No safe conclusions were drawn regarding the effect of biodiesel on particle number emissions from DPF equipped vehicles and a trend towards lower solid particle emissions with biodiesel concentration increase is indicated for the non-DPF car. A shift towards lower mobility particle diameters was observed with the increase of biodiesel concentration.