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33 uses the same models and data. Therefore, it is recommended CO2 emissions = (1 h ) (10, 000 g CO2 h ) that USEPA's NONROAD2005 (or CARB's OFFROAD2007 = 10, 000 g CO2 . This equates to for airports in California) be used to determine emission fac- 0.01 metric ton when using a conversion tors for representative equipment as shown in Figure 3-15 factor of 0.000001 metric ton g.. (USEPAc 2005 and CARBa 2007). To use emission factors from this model, the airport oper- Emission factors for CH4 and N2O are provided by both the ator is required to identify the specific construction vehicles USEPA's Climate Leaders and IPCC for various non-highway that would be deployed on the construction, as well as the an- mobile sources (e.g., small utility, large utility, etc.). The nual hours of use, equipment horsepower, and load factor. emission factors can be found in the Climate Leaders mobile This information is further described in the user's manuals source inventory guidance document (USEPAa 2008) and for the models. Volume 2, Chapter 3 of the IPCC 2006 inventory guidance In modeling these emission factors, reasonable approxi- (IPCC 2006). Since the IPCC data represent international de- mations may need to be made based on the data available in faults, the USEPA's data are preferred. It is up to the inventory NONROAD and knowledge of the local construction vehicle developer to determine the appropriateness of this informa- mix. The inventory developer needs to make this determina- tion in estimating emissions for construction equipment. tion based on knowledge of the specific equipment used at the For construction equipment that has air conditioning, the airport. Alternatively, emission factors could potentially be IPCC provides a method to derive emissions for HFC and obtained directly from the manufacturers. Although this PFC based on default parameters related to mobile air condi- would be a time-consuming effort, it would provide im- tioning. The IPCC methods can be found in Volume 3, Chap- proved emissions estimates. Potentially, manufacturer spec- ter 7 of the IPCC 2006 guidelines (IPCC 2006). Both the ification sheets could also provide useful information in USEPA Climate Leaders (USEPAc 2008) and TCR (TCRa matching a construction vehicle to an appropriate equipment 2008) provide simplified explanations and emission factors type in NONROAD. based on the same information from IPCC. Once the emission factors are known, activity information The overall method is based on material balancing of the needs to be estimated. Since emission factors from NON- emissions, taking into account the charging, operating, and ROAD are provided in grams per break horsepower-hour, disposal of refrigerants. The USEPA Climate Leader's simpli- suitable load factors would need to be used. If the loading fied view of the emission factors and related parameters is pre- data are not available, assumptions could be made based on sented in Table 2 of their Refrigeration and Air Conditioning the inventory developer's experience. emissions guidance document (USEPAc 2008). The inventory The following provides an example calculation assuming developer will need to determine if this method is warranted 1 h activity for one piece of construction equipment: and the corresponding data are appropriate for the airport. For the other pollutants in Level 3 (beyond the six Kyoto pollutants), NONROAD2005 (USEPAc 2005) or similar mod- els like OFFROAD2007 (CARBa 2007) can be used to predict NONROAD2005 emission factors. The pollutants include various gases and or Other Models PM. Emissions of H2O and SOx can potentially be estimated using fuel composition data with mass balance as indicated in Appendix C. Construction Emission Equipment Factors Activity Data 3.9 Other Airport Sources The preceding sections identify the common sources of GHG emissions at an airport. Since every airport is different, Calculate it is likely that there are unique sources operating at an airport that are not captured in the preceding sections. Therefore, the Guidebook recommends that the inventory developer con- Construction sider the principles noted in the previous sections in devel- Activity GHG Emissions oping a methodology to capture the emissions from other sources (i.e., making logical choices of using appropriate Figure 3-15. Overview of GHG emission factors and applying them to the associated activity emissions calculations for data for each source). The methodology should be clearly doc- construction activities. umented in the text that accompanies the resulting inventory.