Abstract Recent research has shown that emissions of some criteria pollutants e.g., particulate matter (PM), CO, and SO$_2 from biodiesel are less than those from petrodiesel. However, studies have also indicated that unregulated toxic emissions like carbonyls from biodiesel are higher compared to those from petrodiesel. Also, there is little information concerning the interaction of biodiesel exhaust PM with atmospheric oxidants such as ozone. The oxidation products of ozone/biodiesel PM reaction could have more severe health and environmental impacts than the primary emissions.
An Armfield CM-12 Automotive Diesel Engine operated in an aggressive cycle driving mode was used to generate PM from various biodiesel feedstocks (soybean, canola, and animal fat). The PM emissions were sampled by a variety of instruments: engine exhaust particle sizer, EEPS (TSI Model 3090) for measuring particle size distributions between 5.6 and 560 nm in real-time; electrical low pressure impactor, ELPI (Dekati LTD) for particle mass distributions, size-resolved chemistry and number concentrations between 7 nm and 10 micrometers; Teflon filters for gravimetric mass, and quartz fiber filters (QFF) for chemical analysis of the exhaust PM using gas chromatography mass spectrometry (GCMS). The polar fraction of primary biodiesel exhaust PM (soybean B20) was found to be 60.8% of the non-polar fraction in the elutable organic mass, while the polar fraction of primary diesel exhaust (B00) was 6.8% of the non-polar fraction in the elutable organic mass. These results show that exposure to primary biodiesel exhaust PM may lead to a higher oxidative stress than exposure to primary diesel exhaust PM.
Biodiesel PM was further exposed to different ozone concentrations over a 24-hour period at room temperature to determine and quantify the products of the reactions between ozone and the biodiesel exhaust PM. Carbonyls, carboxylic acids, PAHs, and quinones are the compounds quantified in these experiments.