Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories (2009)

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49 1. Question: Why should an airport prepare a GHG inventory and what are the benefits of having one? Answer: Currently, GHG inventories are voluntary on a national level, but there may be state or local requirements to prepare an inventory. Such local requirements could be to (1.) include the inventory in a climate action plan, (2.) meet a local requirement to register a governmental entity’s emissions in a climate registry, (3.) meet a state NEPA-like disclosure requirement. All other inventories would likely be voluntary. Section 1.4 of the Guidebook discusses the categories of inventories. The benefits of preparing an inventory include: being prepared for future legislation and related requirements, understanding emissions and fuel consumption-related efficiencies, and demonstrating environmental leader- ship. By preparing GHG inventories over time, an air- port can consider trends and compare these inventories against other airport inventories as well as other emission sources. 2. Question: What sources are to be captured in the airport inventory? Answer: The sources to be reflected in an inventory depend on the purpose of the inventory. As discussed in Sections 2.1 to 2.4 of the Guidebook, a climate action inventory generally reflects all sources that operate at an airport, ranging from aircraft to GSE to GAVs, etc. The geographic boundary of the inventory ranges from departing aircraft (the entire flight segment from the airport to its destination) to ground access vehicles for the entire ground movement associated with the air travel (such as the ground travel to arrive at the airport and then return upon completion of the air travel). To enable the inventory to be policy relevant (a term used by various organizations to reflect the influence that an entity can have over the emissions), sources reflected in the inventory should be categorized by ownership and control. Thus, the sources that are owned and controlled by the airport operator should be noted first, followed by the sources owned and controlled by the airport tenants (airlines, fixed-based operators, concessions, etc), fol- lowed by other ground access vehicular access to the airport, referred to as the public category. For inventories prepared for purposes of a sustainability plan or NEPA-like state requirements, the inventories will typically focus on a subset of sources that are affected by the plan or the airport project. These inventories can present emissions using the same approach that is used for climate action plans, but limited to the sources reflected in the plan or project. Alternatively, sources can be reported as Scope 1, 2, or 3, which are shown in Table 2-2 of the Guidebook, relative to the specific sources, as follows: Scope 1/Direct emissions are from sources that are owned or controlled by the reporting entity. For an airport, the Scope 1 emissions would be those associated with ground vehicles owned and operated by the airport, as well as stationary sources. Scope 2/Indirect emissions are those from the generation of purchased electricity consumed by the entity. Scope 3/Indirect and Optional emissions are a con- sequence of the activities of the entity, but occur at sources owned or controlled by another party. Scope 3 would be the largest quantity of emissions at an airport, as they would include aircraft-related emissions, emis- sions from all tenant-related activities (including aircraft operations and the associated ground support activities) as well as the public’s ground travel to and from the airport. Frequently Asked Questions

3. Question: For what emissions is the airport operator responsible? Answer: When evaluating ways to reduce emissions, the airport operator would be responsible for emissions that it owns and controls or over which it has some influence. The emissions that the airport owns and controls are the primary responsibility. This is further explained in Section 2.4. 4. Question: How do I ensure that double counting does not occur with flight segments at other airports? Answer: The approach recommended by this Guidebook strives to avoid double counting for all sources. When computing aircraft emissions, unless the airport operator owns aircraft, such emissions are associated with the tenant category and are considered Scope 3. To avoid double counting among airports, the calculation of air- craft emissions is recommended to represent one of the following two approaches: 1. Fuel dispensed at an airport (Method 1 or 2) or 2. If calculating emissions from each flight, only reflect- ing emissions from departures from the airport in Method 3. In this later approach, aircraft emissions should be assessed by individual legs of a flight, rather than the departure and final destination of multi-leg flights. For instance, a flight that leaves JFK, flying to ORD, then to DEN, and then to SFO, should attribute the flight from JFK to ORD to JFK, the flight from ORD to DEN to ORD, and the flight from DEN to SFO to DEN. Section 3.1 of the Guidebook discusses the methodology associated with all of these methods. 5. Question: Won’t including aircraft emissions for an entire flight (i.e., attributing all of a flight’s emissions to the departure airport) give the wrong impression that the particular airport and jurisdiction is responsible for GHGs other than occurring within the jurisdiction? Answer: Since the attribution of a flight’s emissions is to the departure airport, the emissions are no longer “centered” around the airport as they are for criteria pollutants under the LTO cycle. As a result, this geographic distortion must be understood when policy decisions are made concerning the attribution of emissions to airports. This Guidebook currently follows the IPCC methodology in attributing all of a flight’s emissions to the departure airport, which— when used uniformly—results in the prevention of double counting and consistency with the national EPA inven- tories. Section 2.5 provides further information on this issue. 6. Question: Do I need to account for emissions above the mixing height (e.g., 3,000 ft or 914.4 m)? Answer: Unlike criteria pollutants, GHGs emitted below the mixing height have an affect on global climate change; criteria pollutants emitted under the mixing height gen- erally exert their primary effects locally. Therefore, the approach recommended to compute aircraft emissions reflects the emissions that occur below the mixing height as well as above. Aircraft Method 1 (using fuel-dispensed data) captures the fuel necessary to power aircraft from one airport to another. Method 2 uses the Method 1 quantity, but separates the emissions from below the mix- ing height versus above (with the LTO reflecting emissions below the mixing height). Method 3, as is expected to be provided annually by the FAA, will present emissions in the following three areas: ground, ground to 3,000 ft, and above 3,000 ft. Section 3.1 of the Guidebook discusses the procedures associated with all three methods. 7. Question: Should emissions reductions from recycling be included? Answer: Most airports have employed some form of recycling including passenger-related internal terminal waste, concessions food waste, construction materials and debris, etc. The Guidebook’s Section 3.6 provides methods that would enable the airport to capture the emissions reduction benefits associated with recycling (waste management) activities. 8. Question: Should indirect emissions (e.g., electricity generation off airport property) be accounted for in the inventories? Answer: In general, the answer to this depends on the purpose of the inventory. For climate action plan-type inventories, yes, indirect emissions should be captured. For project-related and sustainability plan inventories, this will depend on the project. Section 3.5.3 of the Guidebook pro- vides an approach to account for electricity, which is con- sidered a Scope 2 emission (see Section 2.2.2), if acquired from local power companies. Most airports purchase electricity from the grid, but those that generate their own electrical power through the consumption of various fossil fuels would report such fuel consumed to generate electricity as Scope 1. WRI and the various registries reflect electrical power acquired as Scope 2 (indirect) emissions. 9. Question: Why is there a difference in approaches for developing inventories for criteria pollutants and GHG gases? Answer: The international regime for computing criteria pollutants (carbon monoxide and ozone precursors) 50

evolved to its current approach, which reflects local emissions (emissions within the mixing height, gener- ally under 3,000-ft elevation) that occur by the main source categories of aircraft, GSE, GAV, and stationary sources. Learning from this approach, the international approach to quantifying GHGs has evolved to reflect similar inven- torying methods, but based on ownership and control. As is reflected in several of the documents supporting this approach, the inventory should relate to the ability of various parties to effect change and reduce emissions associated with the source. This is further discussed in Sections 1.7 and 2.4. Also, unlike criteria pollutants, the effects of GHGs cannot be attributed to a specific location (e.g., an “airport boundary”). As explained in Section 2.5, GHG emissions from aircraft and vehicles influenced by the airport need to be accounted for irrespective of where those emissions occur (e.g., beyond the airport boundary and above the mixing height). 10. Question: How do the results of this Guidebook compare with the online carbon calculators for air travel? Answer: A number of evaluations have been conducted by various parties; some of these are publicly available on Internet sites. As many of these reviews have shown, a user may get one result with one online calculator and a different result with another. These calculators are pri- marily designed to provide the user the emissions from one person’s air travel, principally associated with aircraft usage. In contrast, the inventory produced using this Guidebook is designed to capture all of the emissions from sources at an airport (not just single flights), with aircraft likely to be the dominant source. The results of an airport inventory are not easily compared with those of an online calculator unless the airport inven- tory can identify the average flight distance of flights at an airport. 11. Question: Why do online carbon calculators use a Radiative Forcing Index (RFI) and how do these relate to the methods in the Guidebook? Answer: Several online calculators employ an RFI to account for many of the unknowns about the effects of aircraft emissions on climate change and some incorrectly use the RFI. The Guidebook does not recommend the use of an RFI for airport-related GHG inventories. Rather, similar to protocols for other industries, this Guidebook recommends that at a minimum, Level 1 inventories be prepared to show CO2 emissions. For the standard Level 2 inventories, reflecting emissions of the six Kyoto GHGs, a CO2 equivalent (CO2e) is to be generated, reflecting the potential effect that non-CO2 pollutants have on climate change, through the use of Global Warming Potentials (GWPs). As indicated in Section 3.8, the IPCC Fourth Assessment Report GWPs are suggested, but GWPs from older IPCC reports (e.g., Second Assessment Report) may be used for consistency with previous inventories and/or other protocols. Appendix D contains a discussion of RFI, GWPs, and other metrics. 12. Question: The Guidebook recommends calculations for all sources. What should I do if data are not available for a specific source? Answer: The Guidebook identifies a preferred method for the quantification of emissions for each source category. It was recognized that not all airports may have data at this level of detail, and thus, alternative methods are identi- fied, some of which require lesser quantities of data. The Guidebook recommends using the highest level of data available for each source so as to aid in identifying key (major) sources. 13. Question: Is it acceptable to use the preferred methods for certain sources and alternative methods for other sources? Answer: Yes. The Guidebook recommends using the high- est level of data available for each source so as to aid in identifying key (major) sources. Each data source and the methods that are used should be clearly documented by the developers of the inventory. 14. Question: Should multiple formats be used to report the airport inventory? Answer: This depends on the purpose of the inventory. The Guidebook recommends that the documentation specifying the inventory note the methods and sources that are commensurate with the reporting format. Some airports may wish to report their emissions in a simple format whereas others may wish to use multiple formats. For instance, if an airport chooses to report their inven- tory to TCR, the format for this registry must be used. However, to aid the airport in understanding and moni- toring its emissions, the airport may choose to have an alternative planning format. 15. Question: For aircraft emissions, the FAA AEDT/SAGE data source presents current (historical) emissions. How should I estimate future aircraft emissions? Answer: Airports can estimate future emissions in a num- ber of ways. First, Aircraft Methods 1 and 2 are available to 51

airports for use if forecasts of fuel dispensed are available. Many airports increase existing fuel-dispensed quantities in proportion to the change in aircraft operations over time. Some airports have aviation activity forecasts that would enable use of Method 2 for future years. Although Methods 1 and 2 are not preferred, they are acceptable alternative methods. 16. Question: For aircraft emissions, the FAA AEDT/SAGE data source presents emissions assuming the mixing height is 3,000 ft. At my airport, the mixing height is not 3,000 ft. Does this matter? And if so, where? Answer: No. The FAA source is provided to enable all airports to have access to a common source of aircraft emissions using the IPCC Tier 3 method, referred to in the Guidebook as the preferred Aircraft Method 3. The fact that the mixing height is different from the 3,000-ft height does not affect the GHG inventories since the total AEDT/SAGE GHG data (above and below 3,000 ft) for an airport still represents the total GHG emissions from aircraft. In evaluating criteria pollutants, some airports use the local mixing height in their modeling as recommended by USEPA and state air agencies. Therefore, should an airport choose to generate a Level 2 or Level 3 pollutant evaluation reflecting criteria pollutants using a different mixing height, these airports should note the different as- sumptions in the documentation. This would not affect the total emissions for aircraft, but would affect the subset of total emissions reported for “ground to 3,000 ft” and “above 3,000 ft.” 52