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21 and emissions associated with all modes of flight includ- CO2 Emissions = ( 20,000 gal ) ( 21.095 lbs CO2 gal ) ing cruise. = 421, 900 lbs CO2 Section 2.3 of this report discussed three levels of evaluation To convert pounds to metric tons, the total pounds of CO2 relative to various pollutants. For aircraft, sources of prepar- should be multiplied by 0.0004536 metric tons/lb. Thus, ing a Level 1 inventory (CO2 only) or Level 2 inventory (all six Kyoto pollutants) were identified. As information for many 421,900 lbs CO2 0.0004536 metric tons lb criteria pollutants is generally not available for all phases of = 191.4 metric tons CO2 aircraft flight, a complete Level 3 analysis is not possible. It is important to note that some fuel sales are reported in 3.1.1 Aircraft Method 1 pounds of fuel sold and not in gallons. Depending on local conditions, 1 gal of Jet A fuel generally weights 6.84 lbs, but This method relies on the use of aircraft fuel sales data with Avgas (100LL) generally weighs 6.0 lbs/gal. These conversions appropriate emission factors to calculate emissions. Aircraft are recommended to ensure calculation consistency. fuel sales refers to the gallons or pounds of fuel dispensed at Similar to CO2 calculation, emissions of CH4 and N2O can an airport, sometimes called aircraft fuel uplift (uplifted to be calculated using the following generic emission factors aircraft). Although this is the overall method, as shown in Figure 3-1, two GHG quantification approaches are described provided by the USEPA's Climate Leaders (USEPAa 2005), exemplifying the use of different conversion factors. The which have been adopted by TCR: choice of these two methods depends on how the fuel sales data are reported. These data may be obtained from several Jet fuel = 0.27 g CH4/gal fuel, organizations, including the airport properties division, the Aviation gasoline = 7.04 g CH4/gal fuel, fuel consortium, airport fixed-based operators, etc. If they Jet fuel = 0.21 g N2O/gal fuel, and cannot provide the data directly, it is likely that they will be Aviation gasoline = 0.11 g N2O/gal fuel. able to specify the appropriate contact. For this calculation, the inventory developer must obtain Thus, for the 20,000 gal of Jet A fuel in the preceding ex- total fuel sales data, which is typically available from the fuel ample, 5,400 g of CH4 (20,000 gal 0.27 g/gal = 5,400 g) providers at an airport. This information can then be con- and 4,200 g of N2O (20,000 gal 0.21 g/gal = 4,200 g) would verted to CO2 emissions using typical emission factors such be emitted. as the following: The quantity in grams can be converted to metric tons by multiplying the grams by 0.000001 metric ton/g. Thus, in Jet A fuel = 21.095 lbs CO2 per gallon Jet A (EIA 2008) and the example, 0.0054 ton of CH4 and 0.0042 ton of N2O would Avgas = 18.355 lbs CO2 per gallon of Avgas (EIA 2008). be emitted. The use of fuel sales data will prevent double counting at The following provides a sample calculation assuming each airport since only the fuel used at an airport (i.e., for 20,000 gallons of Jet A fuel consumption: departure) will be used to represent GHG emissions at that airport. None of the methods recommended herein account for fuel tankering as such data are not publicly available. Emission Factors Fuel tankering is the practice of purchasing more fuel than Airport Fuel and Other Data as Sales Data necessary to fly an aircraft from one airport to the next. In Necessary general, it represents an economic strategy to take advantage of lower fuel costs in certain regions. Depending on where the tankering is conducted (i.e., based on fuel prices at dif- Calculate ferent locations), a GHG inventory could either under- or overestimate aircraft GHG emissions from departure flights at an airport when using fuel sales data. An issue to be considered in using fuel sales data is whether Total Aircraft GHG the inventory should or needs to identify the effects of vari- Emissions ous policies such as fuel taxes. For an airport located in city X (Airport X), if a notable number of flights tanker fuel, the Figure 3-1. Overview of emissions quantified using fuel sales could be understated rel- Aircraft Method 1. ative to the fuel required to power flight for Airport X. Thus,