Table C-2. APU Fuel Usage Rates  Equation C-6. Fuel Usage for APU  Fuel Usage (gallons)  =  Fuel Flow Rate (pounds per hour) x Operating Time (minutes) x number of  operations x 1 hour per 60 minutes / 6.84 pounds per gallon  Equation C-6  ( Fuel Usage for APU ) shows the calculation for computing APU fuel usage  in  gallons.  Once the APU fuel usage (in gallons) is determined, the emission factor for Jet A – startup mode  in  Table C-1  ( GHG Emission Factors for Aircraft Fuel ) should be used to determine the CO$_{2}$,  CH$_{4}$, and N$_{2}$O emissions, which should then be adjusted to account for GWP using  Equation C­ 5  ( CO$_{2e }$ Emission Calculation for Turbine Aircraft during Startup )  with a result of  CO$_{2e }$ (in  metric tons).  The following section discusses the methodologies for computing  GHG emissions associated  with GSE.  GSE include aircraft tugs, baggage tugs, fuel trucks, food trucks, cargo trailers, water  trucks, lavatory trucks, cabin service, belt loaders, and cargo loaders.  Some airports collect GSE fuel usage data within its recordkeeping system (often through a fuel  consortium or fixed based operator). These records provide the most accurate accounting of GSE  fuel usage. However, a t some airports, fuel use  records are not available or reliable. For these  conditions, GSE fuel usage should be estimated based on the fuel flow rates (in grams 67$_{ }$ C.2.3 Ground Support Equipment  Description  Fuel Usage  (pounds/hour)  APU PW901A  863  APU ST-6  440  APU T-62T-27 (100 HP)  102  APU T-62T-47C1  235  APU TSCP 700 (142 HP)  463  APU TSCP700-4B (142 HP)  463  APU WR27-1  140  APU GTCP 165-9(135 HP)  100  APU GTCP 165-1A(128 HP)  95.1  APU GTCP 331-250  106  APU 85-180(177 HP)  132  APU T62T27(65 HP)  48.3  Source: FAA’s EDMS, 2013.  APPENDIX C$_{ }$