EFFECTS OF BIODIESEL BLENDING ON EXHAUST EMISSIONS

Abstract

Rising fuel costs and energy demands, combined with growing concern over health related and environmental concerns, have led to increased interest in the use of biodiesel. Biodiesel can be utilized as a direct replacement for conventional petroleum diesel or mixed with it to create blended fuels. This latter practice is quite common, as many existing engines are only certified for use with fuels containing a maximum of 5-20% biodiesel. Fuel blending results in the production of a fuel with chemical makeup and combustion properties that may differ significantly from either original source. Understanding the effects of this blending process on engine exhaust composition is an important component of assessing the suitability of these fuels for use in on- and off-road diesel engines. Research shows that the use of biodiesel made from various feedstocks can reduce the emission of total hydrocarbons (THC), carbon monoxide (CO), and particulate matter (PM), but there is often some increase in nitrogen oxides (NOX) emissions. Since the composition of this biodiesel may vary depending on the specific feedstock used, it is important to determine the relationship between fuel composition and the resulting emissions of regulated and particle-bound air pollutants during combustion. The goal of this study is to assess the effect of increased biodiesel concentration, and the resulting changes in fuel properties on criteria pollutants and particle-bound metal emissions from three off-road diesel engine emissions, which include a lawn mower, a diesel generator, and a switching locomotive. The dissertation is comprised of three sections. In the first section, the lawn mower and the diesel generator were powered by used cooking oil based biodiesel blending, while the emissions profiles for CO2, CO, NOX, THC and PM-bound chemicals were measured. The results show that both the engine and fuel properties affected the NOX and THC emissions, which decreased with increasing biodiesel percentage in the test fuels from both engines. In the second section, up to B20 blends of two kinds of biodiesel (soybean and tallow) were used successfully for extended periods of time in currently-operating locomotives without engine modifications. Biodiesel generally had a lower heating value and less THC emissions. There was no apparent trend for NOX emissions. In the last section, a rapid-assessment method using LA-ICP-MS method was developed to directly analyze the particle-bound metal for diesel and biodiesel particulates at two running conditions.