Energy and Environmental Viability of Select Alternative Jet Fuel Pathways

Abstract

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 NO X emissions from military aircraft tend be lower while primary PM 2.5 , 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 CO 2 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.

The impact of advanced biofuels on aviation emissions and operations in the U.S.

“…Under the original target, 50% of the Air Force's total domestic aviation fuel use was to be met by fuel blends that included alternative fuels that are "greener"-presumably in terms of GHG emissions-than conventional counterparts (U.S. Air Force, 2009). Carter et al (2011) calculate that this target equates to 370 million gallons of renewable fuel per year. Under the revised target, 50% of fuel used for non-contingency operations must be blended with alternative fuel (U.S. Air Force, 2013), but non-contingency is not specified.…”

“…These include high production costs and lack of integration of aviation biofuels into regulatory frameworks (Carter et al, 2011, Carriquiry et al, 2011Gegg et al 2014), limits in scale-up due to feedstock availability (U.S. DOE, 2011, Seber et al, 2014, environmental and socio-economic consequences of large-scale land-use change and competition with food and feed needs (Searchinger et al 2008;Kretschmer et al, 2009;Serra and Zilbermann, 2013), water consumption associated with biomass cultivation (Scown et al, 2011, Staples et al, 2013, and the time required for scaling-up biomass cultivation and conversion facilities (Richard, 2010). This paper deals with the impact of large-scale deployment of advanced aviation biofuels from perennial grasses such as switchgrass or miscanthus using a set of technologies known as advanced fermentation.…”

Life-Cycle Analysis of Alternative Aviation Fuels in GREET

“…The emissions values listed in Tables 10 and 13 are derived from the fuel-burn-weighted averages for the CFM56 and PW308 engines described in TABLE A-2; these averages were applied to the emissions changes from various SPK fuel blends, as shown in Corporan et al 2007;Corporan et al 2009;Corporan et al 2010a,b;Lobo et al 2011;Moses et al 2003;Timko et al 2010). A summary of these SPK fuel combustion emissions values can be found in Carter et al (2011). Note that all SO x emissions are assumed to be a function of fuel composition and that 50 percent and 100 percent SPK corresponds to a 50 percent and 100 percent reduction in fuel sulfur content compared with conventional jet fuel, respectively.…”

Life cycle greenhouse gas analysis of biojet fuels with a technical investigation into their impact on jet engine performance

“…For instance, most studies have adopted transportation (feedstock/fuel product) based emissions related to Conv. Jet fuel for the biofuels as well [9,10,12,15]. When the CO 2 equivalents of GHG emissions is measured as g MJ À1 of fuel (the functional unit of this study), adoption of standardised emission figures neglects the fuel's energy factor thus affecting the fidelity of this study.…”

“…Microalgae SPK [10e13] and Jatropha SPK [14,15] have been conducted earlier. These studies were elaborately focussed on the GHG emission attributable to the life cycle processes of biofuels (renewable diesel and hydrotreated renewable jet fuel).…”