Influence of Oxidized Biodiesel Blends on Regulated and Unregulated Emissions from a Diesel Passenger Car

This paper investigates the effects of biodiesel blends on regulated and unregulated emissions from a Euro 4 diesel passenger car, fitted with a diesel oxidation catalyst and a diesel particle fitter(DPF). Emission and fuel consumption measurements were conducted for the New European Driving Cycle (NEDC) and the Artemis driving cycles. Criteria pollutants, along with carbonyl, polycyclic aromatic hydrocarbon (PAH) and nitrate PAH and oxygenate PAH emissions, were measured and recorded. A soy-based biodiesel and an oxidized biodiesel, obtained from used frying oils, were blended with an ultra low sulfur diesel at proportions of 20, 30, and 50% by volume. The results showed that the DPF had the ability to significantly reduce particulate matter (PM) emissions over all driving conditions. Carbon monoxide (CO) and hydrocarbon (HC) emissions were also reduced with biodiesel; however, a notable increase in nitrogen oxide (NOx) emissions was observed with biodiesel blends. Carbon dioxide (CO2) emissions and fuel consumption followed similar patterns and increased with biodiesel. The influence of fuel type and properties was particularly noticeable on the unregulated pollutants. The use of the oxidized biodiesel blends led to significant increases in carbonyl emissions, especially in compounds which are associated with potential health risks such as formaldehyde, acetaldehyde, and acrolein. Sharp increases in most PAH compounds and especially those which are known for their toxic and carcinogenic potency were observed with the oxidized blends. The presence of polymerization products and cyclic acids were the main factors that influenced the PAH emissions profile.