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19 CHAPTER 3 Emissions Calculations and Application of CO2 Equivalencies This chapter provides instructions on how to calculate GHG being up to date and specific to each fuel type. For example, emissions and CO2 equivalencies. The sections are arranged emission factors for some of the lesser-used fuels (e.g., ethanol, by source with emissions calculations followed by calcula- biodiesel, etc.) can be found in the same sources that provide tion procedures for creating CO2 equivalencies. Further back- data for gasoline and diesel. ground information on the methods used can be found in The inventory developer is also responsible for determining Appendices C and D. when to use more appropriate (i.e., more specific, as reflected Since the majority of GHG emissions at most airports is in the highest method level) data when available rather than generated by aircraft and GAVs, different methods of evalu- more generalized data (as related to a lower method level). It ation for these specific sources are provided. For aircraft and is not the intention of this Guidebook to suggest a single set GAV, the evaluation focused mainly on three of the six Kyoto of emission factors but to allow the inventory developer to pollutants (CO2, CH4, and N2O), since these sources emit little determine the most appropriate emission factors based on or no amount of the other pollutants (HFC, PFC, and SF6). the needs of the emissions inventory. In large part, this is due to the lack of data for these other pol- lutants. In general, if the data are lacking (or not established) for a pollutant in each source category, that pollutant is not addressed in the respective section. The purpose of the Although guidance is provided on how to cal- culate GHG emissions, the inventory developer is method levels and the structure of this Guidebook is to pro- ultimately responsible for making sure the data vide airport operators with evaluation methods that can be and methods presented herein (or referred to) matched with the resources and data that are most com- are appropriate for the airport. monly available. Generally, the higher the method number, the more detailed the data that are required to undertake the analysis. Most of the emissions calculations for each source are based Although the use of continuous emissions monitoring on estimating or obtaining fuel use (or activity) information (CEM) equipment to more accurately determine emission and then multiplying by the appropriate GHG emission factor, factors might be possible for some sources, this Guidebook as follows: does not directly address their use. CEM use is feasible for some sources (e.g., stationary sources), but the use of mea- Emissions = ( fuel use or activity ) ( emission factor ) sured data is not necessary for airport inventories because the data for significant sources (e.g., aircraft and GAVs) either are Emission factors should be obtained from reliable sources usually available or reasonable approximations of them can such as IPCC, EIA, USEPA, etc. Emission factors from these be made. different sources may vary but the differences will likely be This Guidebook identifies preferred methods for each source small. For consistency, the same data sources and methods to prepare inventories. Recognizing that one size does not should be used, especially if tracking changes over time. Some always fit all, alternate methods are also identified, especially representative emission factors are presented in the following for situations where data are not available to enable use of the sections, but it is the inventory developer's responsibility to preferred method. Table 3-1 summarizes the preferred and make sure all emission factors are appropriate; this includes alternate methods for each source documented in the follow-