title: Aircraft emissions of methane and nitrous oxide during the alternative aviation fuel experiment.
abstract: Given the predicted growth of aviation and the recent developments of alternative aviation fuels, quantifying methane (CH(4)) and nitrous oxide (N(2)O) emission ratios for various aircraft engines and fuels can help constrain projected impacts of aviation on the Earth's radiative balance. Fuel-based emission indices for CH(4) and N(2)O were quantified from CFM56-2C1 engines aboard the NASA DC-8 aircraft during the first Alternative Aviation Fuel Experiment (AAFEX-I) in 2009. The measurements of JP-8 fuel combustion products indicate that at low thrust engine states (idle and taxi, or 4% and 7% maximum rated thrusts, respectively) the engines emit both CH(4) and N(2)O at a mean ± 1σ rate of 170 ± 160 mg CH(4) (kg Fuel)(-1) and 110 ± 50 mg N(2)O (kg Fuel)(-1), respectively. At higher thrust levels corresponding to greater fuel flow and higher engine temperatures, CH(4) concentrations in engine exhaust were lower than ambient concentrations. Average emission indices for JP-8 fuel combusted at engine thrusts between 30% and 100% of maximum rating were -54 ± 33 mg CH(4) (kg Fuel)(-1) and 32 ± 18 mg N(2)O (kg Fuel)(-1), where the negative sign indicates consumption of atmospheric CH(4) in the engine. Emission factors for the synthetic Fischer-Tropsch fuels were statistically indistinguishable from those for JP-8.
authors: School of Engineering and Applied Sciences and Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St., Cambridge, Massachusetts 02138, USA. gsantoni@gmail.com
authors: Gregory W
authors: GW
authors: Santoni
authors: Ben H
authors: BH
authors: Lee
authors: Ezra C
authors: EC
authors: Wood
authors: Scott C
authors: SC
authors: Herndon
authors: Richard C
authors: RC
authors: Miake-Lye
authors: Steven C
authors: SC
authors: Wofsy
authors: J Barry
authors: JB
authors: McManus
authors: David D
authors: DD
authors: Nelson
authors: Mark S
authors: MS
authors: Zahniser
mesh_terms: D000401:Aircraft; D002245:Carbon Dioxide / Q000032:analysis; D003198:Computer Simulation; D006813:Humidity; D006838:Hydrocarbons / Q000032:analysis*; D008697:Methane / Q000032:analysis*; D009609:Nitrous Oxide / Q000032:analysis*; D013696:Temperature; D013997:Time Factors; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D006838:Hydrocarbons; C098607:JP8 aviation fuel; D001335:Vehicle Emissions; D002245:Carbon Dioxide; D009609:Nitrous Oxide; D008697:Methane