Aviation has the capacity to drive changes in atmospheric composition, and therefore climate and air quality, increasing human mortality through increases in cases in cardiopulmonary disease. Non-CO2 aviation emissions are estimated to have a considerable effect on the climate, and with rapid growth in the aviation sector their associated impacts could increase. There is much uncertainty surrounding the climatic impact of aviation-induced ozone and aerosols, in part due to broad range of emissions species emitted, which are not always reported in aviation emissions inventories.
This thesis assesses the impact of aviation on atmospheric trace gas and aerosol concentrations, climate, air quality and human health effects for year 2000 civil aviation. These impacts are estimated through: (i) the development of an extended aviation emissions inventory, inclusive of speciated hydrocarbons; (ii) assessing the atmospheric and climatic impact from aviation based on an extend aviation emissions inventory, a comparison of these impacts with a reduced emissions aviation emissions inventory, along with a sensitivity study for emissions species included; (iii) assessing the impact of aviation on human health effects when variations in fuel sulfur content (FSC) are applied along with resulting impacts on radiative effects, and; (iv) the atmospheric, climatic, air quality and human health impacts of the use of alternative fuels in aviation.
An aviation emissions inventory was developed to represent aviation-borne non-CO2 emissions: nitrogen oxides, carbon oxide, speciated hydrocarbons, sulfur dioxide, black carbon and organic carbon emissions while taking in to account the geometric mean diameter of carbonaceous particles released. Aviation non-CO2 emissions are assessed to result in a radiative effect of –13.29 mW m-2 [assessed from the ozone (O3DRE) and aerosol (aDRE) direct radiative effects, and aerosol cloud albedo effect (aCAE)], primarily driven by a cooling aCAE. In comparison an emissions inventory which only considers aviation nitrogen dioxide and black carbon emissions results in a radiative effect of –8.19 mW m-2 primarily driven by reductions in the cooling aCAE assessed.
It is found that air pollution from aviation reaches ground level, as such modifying surface PM2.5 (particulate matter within the 2.5 μm size range) which results in increased human exposure. Standard aviation is estimated to result in 3597 mortalities a-1. Variations in FSC from 0–6000 ppm aviation’s human health effects range from 2950–9057 mortalities a-1. These variations in FSC result in an aviation non-CO2 radiative effect ranging from –6.08 mW m-2 to –75.48 mW m-2. It is found that variations in aviation FSC elicit a near-linear relationship between aviation-induced mortality and non-CO2 radiative effect. Additional investigations in the vertical release of aviation-borne sulfur dioxide emissions show that it possible to reduce aviation-induced mortality and increase aviation-induced cooling by adjusting the FSC of fuel used at different altitudes.
An investigation of the use of Fischer-Tropsch (FT) and fatty acid methyl ester (FAME) fuels (FT50, FT100, FAME20 and FAME40 fuel blends) within aviation found that aviation-induced nitrogen dioxide and ozone concentrations were reduced in tandem with associated ozone radiative effects. Additionally due relative reductions between sulfur dioxide and carbonaceous aerosol emissions FT fuel blends were estimated to produce negative aDREs, while FAME fuel blends gave a positive aDRE. In all cases FT and FAME fuel blends decreased the aCAE induced cooling effect from aviation. FT50 is the only fuel blend currently specified for use in today’s civil aviation fleet. This fuel blend is simulated to reduce aviation’s non-CO2 emissions cooling radiative effect to –10.89 mW m-2 and reduce aviation-induced mortality by 460 mortalities a-1. Through the sustainable development of FT fuels from bio-sourced feedstocks this fuel blend has the potential to reduce aviation’s climatic impact and human health effects (when reductions in aviation’s net CO2 emissions are considered in tandem).
