Impact of fossil fuel alternatives on internal combustion engine emissions

The increasing demand for alternatives to fossil fuels has raised important questions to scientists and policy makers about changes in emissions from large scale use of biofuels in internal combustion and the associated impacts human health and climate change. The purpose of this dissertation is to assess the impacts of fossil fuel alternatives on emissions of internal combustion engines.;The impact of petroleum and biofuel blends on the particulate matter and non-regulated gases emissions from a non-road heavy-duty diesel vehicle that was not equipped with exhaust after-treatment devices was examined. The emission rates of organic species in the particle-phase and gas-phase were collected from diluted exhaust, and then analyzed to obtain their detailed chemical speciation. From this analysis it was also found that blending petroleum diesel with biodiesel fuels results in reductions of elemental carbon aerosol and increases in organic carbon aerosol emissions. From the analysis of gas phase organic species, it was found that blending petroleum diesel with biodiesel fuels results in significant reductions in emissions of hazardous air pollutants. Since black carbon aerosols are strongly associated with climate change forcing, it was concluded that through the strategic use of biodiesel, is possible to achieve significant reductions in black carbon emissions from diesel-powered vehicles.;From the study of the effects of ambient temperature changes and fuel type on particle number emissions from light-duty spark-ignition vehicles operating on conventional gasoline, blends of gasoline and ethanol, and compressed natural gas, it was found that slight temperature changes do not clearly impact particle number emissions, independent of the fuel type. On the other hand, blending conventional gasoline with ethanol results in important reductions in particle number emissions, once the fuel blend contains more than 65% of ethanol.;Based on the importance of developing consistent black carbon emission inventories, from the study of the effect of dilution on optical black carbon measurements from internal combustion engine sources it was found that dilution plays an important role in the mixing state and aging of carbonaceous aerosol, thus affecting aerosol light absorption characteristics and consequently black carbon optical measurements from internal combustion sources.