Equation C-10  shows the calculation of the motor vehicle CO 2e  emissions as a functi on of  vehicle miles traveled. This calculation can be made for each vehicle type or for a composite  vehicle fleet mix.  If vehicle fuel usage is known (via airport records), then the CO$_{2e }$emissions should be calculated  as a function of the fuel-based emission factors (shown in  Table C-3 ,  GHG Emission Factors for  GSE ). These emission factors should then be applied to determine the CO $_{2}$, CH$_{4}$, and N $_{2}$O  emissions (in metric tons), as shown for an example diesel bus  in  Equation C-11 , ( CO$_{2e }$ Emission Calculation of Diesel Bus ).  The following section discusses the methodologies for computing  GHG emissions from  stationary sources. Stationary sources at an airport which emit GHG emissions include boilers,  generators, snowmelters, and fire training facilities. Storage of fuel (i.e., jet fuel, avgas, gasoline,  and diesel) is a potential source of evaporative hydrocarbon emissions, but does not produce the  types of hydrocarbons that contribute directly to climate change.  Typically,  stationary source fuel usage can be obtained from fuel purchase records, storage tank  throughput, or other records. If fuel usage records are not available,  the fuel usage should be  estimated based on the hours of operation and hourly fuel flow rates for each source  from  manufacturer data.  Equation C-11. CO$_{2e }$Emission Calculation of Diesel Bus  CO$_{2 }$(metric tons)  =  Fuel Usage (gallons) x 22.377 pounds CO$_{2 }$per gallon x short ton per 2,000 pound  x 0.907185 metric ton per short ton  CH$_{4 }$(metric tons)  =  Fuel Usage (gallons) x 0.00128 pounds CH$_{4 }$per gallon x short ton per 2,000 pound  x 0.907185 metric ton per short ton  N$_{2}$O (metric tons)  =  Fuel Usage (gallons) x 0.00057 pounds N$_{2}$O per gallon x short ton per 2,000  pound x 0.907185 metric ton per short ton  CO$_{2e }$(in metric tons) = CO$_{2 }$+ CH$_{4 }$x 34 + N$_{2}$O x 298  C.2.5 Stationary Sources  70$_{ }$ Equation C-10. CO$_{2e }$Emission Calculation for Motor Vehicles  CO$_{2 }$(metric tons)  = VMT (miles) x CO$_{2 }$Emission Factor (grams per mile) x 1 short ton/2,000 pound x  0.907185 metric tons/short tons  CH$_{4 }$(metric tons)  = VMT (miles) x CH$_{4 }$Emission Factor (grams per mile) x 1 short ton/2,000 pound x  0.907185 metric tons/short tons  N$_{2}$O (metric tons)  = VMT (miles) x N$_{2}$O Emission Factor (grams per mile) x 1 short ton/2,000 pound x  0.907185 metric tons/short tons  CO$_{2e }$(in metric tons) = CO$_{2 }$+ CH$_{4 }$x 34 + N$_{2}$O x 298  APPENDIX C$_{ }$