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Source: FAA’s EDMS, 2013. 

Equation C-6 ( Fuel Usage for APU ) shows the calculation for computing APU fuel usage in gallons. 

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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). 

## C.2.3 Ground Support Equipment 

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 

