Energy and Environmental Viability of Select Alternative Jet Fuel Pathways

This paper analyzes alternative jet fuels in terms of how they could change emissions from military and civil aircraft and in terms of the challenges in meeting future energy goals. Estimations of the continental United States (CONUS) conventional jet fuel energy usage for the civil and military aviation fleets were used to inform the magnitude and logistics of where the fuels would be needed. To adequately meet military goals, the U.S. Air Force (USAF) and U.S. Navy (USN) would need to supply roughly 47,500 bpd and 18,800 barrels per day (bpd) of alternative jet fuels by 2016, respectively. The total amount of fuel for both military and civil goals would reach nearly 132,000 bpd within the next decade if tentative goals become actual policy. Quantifications of the emissions affecting surface air quality from CONUS civil, USAF and USN aircraft, as well as 50% and 100% synthetic paraffinic kerosene (SPK) combustion emissions normalized by conventional jet fuels were also provided. Although a 50% blend of SPK has been permitted, additional testing and analysis is needed for approval of higher blend percentages. It was found that NOX emissions from military aircraft tend be lower while primary PM2.5, CO and UHC emissions tend to be higher than their civilian aircraft counterparts. This is indicative of military aircraft being less efficient at lower power settings than civil aircraft during the LTO cycle. Emissions reductions with 50% and 100% SPK use could provide military and civil aviation planners with more options when locating aircraft in nonattainment areas within the CONUS. For some emissions, the introduction of SPK fuels could allow for additional aircraft for the same environmental impact or decreased overall air quality footprint for a particular location. SPK fuels from Fischer-Tropsch Biomass-to-Liquid (BTL) and Hydroprocessed Renewable Jet (HRJ) processes were examined for their ability to meet future alternative fuel and environmental goals. BTL facilities were found to have larger capital costs and HRJ required large land area. Lifecycle analysis (LCA) of greenhouse gas (GHG) emissions for select F-T BTL and HRJ were found to potentially meet or exceed organizational goals in the near term. High yield crops like algae could provide the energy and environmental goals, but additional constraints must be considered, such as water and CO2 requirements; furthermore, these technologies need to be translated from the lab to commercial production. Additional research is required to provide an in-depth geographic analysis of the CONUS commercial and military demand centers and resource constraints to better understand the challenge in meeting future alternative fuel goals.