Oxidized Biodiesel Fuel Composition and Associated Tailpipe Ultrafine Particle Emissions

A number of basic chemical tests are currently used to quantify the oxidative stability of neat biodiesel fuel, but little information exists on how the organic chemical composition of biodiesel changes with oxidation of the fuel’s fatty acid methyl esters (FAMEs). These changes in fuel composition are expected to have important effects on the tailpipe emissions associated with use of biodiesel in real-world fuel blends. This study will (1) determine the chemical composition of B100 and real-world Bxx biodiesel fuel blends by detailed organic gas chromatography-mass spectrometry (GC-MS) analysis at different stages of oxidation and compare the GC-MS results to the American Society for Testing and Materials (ASTM) methods for acid value (AV) and peroxide value (PV) to gain better understanding of the oxidation pathways of FAMEs; and (2) conduct emissions tests on oxidized and unoxidized biodiesel fuels and compare their particle-phase emissions. This study aims to identify the differential oxidation pathways for biodiesel prepared from virgin soybean feedstock to that of recycled waste vegetable oil given that feedstock choice and processing are significant parts of the fuel’s lifecycle analysis.