Non-CO₂ environmental impacts of transportation fuel use and production
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics.
Steven R. H. Barrett, Ian A. Waitz and Ronald G. Prinn.
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Transportation represents one of the largest contributors to anthropogenic air pollution and global climate change. This thesis aims to quantify three specific environmental impacts from transportation fuel combustion and production: 1) Health impacts from transportation combustion emissions in the United States. A multiscale air quality model is applied to assess health impacts from PM 2.5 and ozone concentrations attributable to different transportation modes and other sectors in the U.S. Road transportation is found to be the largest contributor for both pollutant-related mortalities, causing overall 58,000 (90% Cl: 22,800 107,100) early deaths per year. Shipping accounts for 8,800 (90% Cl: 3,700 - 16,100) premature mortalities per year, and rail transportation for 5,000 (90% Cl: 1,900 - 9,300) early deaths. Aviation emissions are responsible for 2,500 (90% Cl: 1,400 - 3,700) early deaths per year in the U.S. 2) Climate effects of albedo changes due to biofuel production. An augmented lifecycle framework is developed to quantify the effects of albedo variations induced by biomass cultivation, and applied to eleven land-use change (LUC) scenarios. Two scenarios are found to have a warming effect, the largest of which is for replacement of desert land with salicornia cultivation. This corresponds to 222 gCO₂e/MJ, equivalent to 3890% and 247% of the lifecycle greenhouse gas (GHG) emissions of fuels derived from salicornia and crude oil, respectively. Nine LUC scenarios exhibit a cooling effect, the largest of which is for the replacement of tropical rainforest with soybean cultivation. This corresponds to -161 gCO₂e/MJ, or -28% and -178% of the lifecycle GHG emissions of fuels derived from soybean and crude oil. 3) Climate impacts from changes in radiative forcing (RF) generated by contrails and contrail cirrus in the scenario of a widespread use of alternative jet fuels in the U.S. The Contrail Evolution and Radiation Model (CERM) is developed to simulate contrail and contrail cirrus cover, properties and radiative forcing over the United States. The results show that the use of alternative jet fuels in the U.S. generates 8% more contrails with respect to conventional jet fuels, due to the enhanced engine water vapor emissions. Contrails from alternative fuels are optically thinner (-35% in optical depth), and formed by larger and fewer ice crystals (+58% in diameter and -73% in number concentration), due to the lower emissions. These differences are responsible for a lower albedo (-36%) from contrails forming as a consequence of alternative fuels emissions. The cooling impact of having optically thinner contrails and is contrasted by the warming effects of having contrails less reflective of the incoming sunlight and in larger number, thus determining a small difference (+0.6%) in the net RF by contrails and contrail cirrus in case of alternative fuels use with respect to conventional jet use. CERM simulations are also performed to quantify for the first time impacts on contrails and contrail cirrus radiative impacts of both combustor technology and ambient conditions, in terms of available concentrations ice nuclei (IN). The results of this thesis offer new insights into the environmental impacts of transportation. The air quality and climate impacts of this sector can be potentially reduced by fostering the use of alternative fuels, but only when previously overlooked effects (such as changes in surface albedo for biofuel production, or ambient concentrations of ice nuclei affecting contrail properties) are taken into account.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2015.Cataloged from PDF version of thesis.Includes bibliographical references (pages 154-165).
DepartmentMassachusetts Institute of Technology. Department of Aeronautics and Astronautics.
Massachusetts Institute of Technology
Aeronautics and Astronautics.