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49 Frequently Asked Questions 1. Question: Why should an airport prepare a GHG an entity can have over the emissions), sources reflected inventory and what are the benefits of having one? in the inventory should be categorized by ownership and control. Thus, the sources that are owned and controlled Answer: Currently, GHG inventories are voluntary on a by the airport operator should be noted first, followed by national level, but there may be state or local requirements the sources owned and controlled by the airport tenants to prepare an inventory. Such local requirements could (airlines, fixed-based operators, concessions, etc), fol- be to (1.) include the inventory in a climate action plan, lowed by other ground access vehicular access to the (2.) meet a local requirement to register a governmental airport, referred to as the public category. entity's emissions in a climate registry, (3.) meet a state NEPA-like disclosure requirement. All other inventories For inventories prepared for purposes of a sustainability would likely be voluntary. Section 1.4 of the Guidebook plan or NEPA-like state requirements, the inventories discusses the categories of inventories. will typically focus on a subset of sources that are affected by the plan or the airport project. These inventories can The benefits of preparing an inventory include: being present emissions using the same approach that is used prepared for future legislation and related requirements, understanding emissions and fuel consumption-related for climate action plans, but limited to the sources reflected efficiencies, and demonstrating environmental leader- in the plan or project. ship. By preparing GHG inventories over time, an air- Alternatively, sources can be reported as Scope 1, 2, or 3, port can consider trends and compare these inventories which are shown in Table 2-2 of the Guidebook, relative against other airport inventories as well as other emission to the specific sources, as follows: sources. Scope 1/Direct emissions are from sources that are owned 2. Question: What sources are to be captured in the or controlled by the reporting entity. For an airport, the airport inventory? Scope 1 emissions would be those associated with ground vehicles owned and operated by the airport, as well as Answer: The sources to be reflected in an inventory stationary sources. depend on the purpose of the inventory. As discussed in Sections 2.1 to 2.4 of the Guidebook, a climate action Scope 2/Indirect emissions are those from the generation inventory generally reflects all sources that operate at of purchased electricity consumed by the entity. an airport, ranging from aircraft to GSE to GAVs, etc. Scope 3/Indirect and Optional emissions are a con- The geographic boundary of the inventory ranges from sequence of the activities of the entity, but occur at departing aircraft (the entire flight segment from the sources owned or controlled by another party. Scope 3 airport to its destination) to ground access vehicles for would be the largest quantity of emissions at an airport, the entire ground movement associated with the air travel as they would include aircraft-related emissions, emis- (such as the ground travel to arrive at the airport and sions from all tenant-related activities (including aircraft then return upon completion of the air travel). operations and the associated ground support activities) To enable the inventory to be policy relevant (a term as well as the public's ground travel to and from the used by various organizations to reflect the influence that airport.
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50 3. Question: For what emissions is the airport operator 6. Question: Do I need to account for emissions above the responsible? mixing height (e.g., 3,000 ft or 914.4 m)? Answer: When evaluating ways to reduce emissions, the Answer: Unlike criteria pollutants, GHGs emitted below airport operator would be responsible for emissions the mixing height have an affect on global climate change; that it owns and controls or over which it has some criteria pollutants emitted under the mixing height gen- influence. The emissions that the airport owns and controls erally exert their primary effects locally. Therefore, the are the primary responsibility. This is further explained approach recommended to compute aircraft emissions in Section 2.4. reflects the emissions that occur below the mixing height as well as above. Aircraft Method 1 (using fuel-dispensed 4. Question: How do I ensure that double counting does data) captures the fuel necessary to power aircraft from not occur with flight segments at other airports? one airport to another. Method 2 uses the Method 1 quantity, but separates the emissions from below the mix- Answer: The approach recommended by this Guidebook ing height versus above (with the LTO reflecting emissions strives to avoid double counting for all sources. When below the mixing height). Method 3, as is expected to be computing aircraft emissions, unless the airport operator provided annually by the FAA, will present emissions in owns aircraft, such emissions are associated with the the following three areas: ground, ground to 3,000 ft, and tenant category and are considered Scope 3. To avoid above 3,000 ft. Section 3.1 of the Guidebook discusses the double counting among airports, the calculation of air- procedures associated with all three methods. craft emissions is recommended to represent one of the following two approaches: 7. Question: Should emissions reductions from recycling 1. Fuel dispensed at an airport (Method 1 or 2) or be included? Answer: Most airports have employed some form of 2. If calculating emissions from each flight, only reflect- recycling including passenger-related internal terminal ing emissions from departures from the airport in waste, concessions food waste, construction materials Method 3. and debris, etc. The Guidebook's Section 3.6 provides In this later approach, aircraft emissions should be assessed methods that would enable the airport to capture the by individual legs of a flight, rather than the departure and emissions reduction benefits associated with recycling final destination of multi-leg flights. For instance, a flight (waste management) activities. that leaves JFK, flying to ORD, then to DEN, and then to SFO, should attribute the flight from JFK to ORD to JFK, 8. Question: Should indirect emissions (e.g., electricity the flight from ORD to DEN to ORD, and the flight from generation off airport property) be accounted for in the DEN to SFO to DEN. Section 3.1 of the Guidebook discusses inventories? the methodology associated with all of these methods. Answer: In general, the answer to this depends on the purpose of the inventory. For climate action plan-type 5. Question: Won't including aircraft emissions for an inventories, yes, indirect emissions should be captured. For entire flight (i.e., attributing all of a flight's emissions project-related and sustainability plan inventories, this will to the departure airport) give the wrong impression depend on the project. Section 3.5.3 of the Guidebook pro- that the particular airport and jurisdiction is responsible vides an approach to account for electricity, which is con- for GHGs other than occurring within the jurisdiction? sidered a Scope 2 emission (see Section 2.2.2), if acquired Answer: Since the attribution of a flight's emissions is to the from local power companies. Most airports purchase departure airport, the emissions are no longer "centered" electricity from the grid, but those that generate their around the airport as they are for criteria pollutants under own electrical power through the consumption of various the LTO cycle. As a result, this geographic distortion must fossil fuels would report such fuel consumed to generate be understood when policy decisions are made concerning electricity as Scope 1. WRI and the various registries reflect the attribution of emissions to airports. This Guidebook electrical power acquired as Scope 2 (indirect) emissions. currently follows the IPCC methodology in attributing all 9. Question: Why is there a difference in approaches for of a flight's emissions to the departure airport, which-- developing inventories for criteria pollutants and GHG when used uniformly--results in the prevention of double gases? counting and consistency with the national EPA inven- tories. Section 2.5 provides further information on this Answer: The international regime for computing criteria issue. pollutants (carbon monoxide and ozone precursors)
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51 evolved to its current approach, which reflects local a CO2 equivalent (CO2e) is to be generated, reflecting the emissions (emissions within the mixing height, gener- potential effect that non-CO2 pollutants have on climate ally under 3,000-ft elevation) that occur by the main change, through the use of Global Warming Potentials source categories of aircraft, GSE, GAV, and stationary (GWPs). As indicated in Section 3.8, the IPCC Fourth sources. Assessment Report GWPs are suggested, but GWPs from older IPCC reports (e.g., Second Assessment Report) may Learning from this approach, the international approach be used for consistency with previous inventories and/or to quantifying GHGs has evolved to reflect similar inven- other protocols. Appendix D contains a discussion of torying methods, but based on ownership and control. RFI, GWPs, and other metrics. As is reflected in several of the documents supporting this approach, the inventory should relate to the ability of 12. Question: The Guidebook recommends calculations for various parties to effect change and reduce emissions all sources. What should I do if data are not available associated with the source. This is further discussed in for a specific source? Sections 1.7 and 2.4. Also, unlike criteria pollutants, the effects of GHGs cannot be attributed to a specific location Answer: The Guidebook identifies a preferred method for (e.g., an "airport boundary"). As explained in Section 2.5, the quantification of emissions for each source category. GHG emissions from aircraft and vehicles influenced by It was recognized that not all airports may have data at this the airport need to be accounted for irrespective of where level of detail, and thus, alternative methods are identi- those emissions occur (e.g., beyond the airport boundary fied, some of which require lesser quantities of data. The and above the mixing height). Guidebook recommends using the highest level of data available for each source so as to aid in identifying key 10. Question: How do the results of this Guidebook compare (major) sources. with the online carbon calculators for air travel? 13. Question: Is it acceptable to use the preferred methods Answer: A number of evaluations have been conducted for certain sources and alternative methods for other by various parties; some of these are publicly available on sources? Internet sites. As many of these reviews have shown, a user may get one result with one online calculator and a Answer: Yes. The Guidebook recommends using the high- different result with another. These calculators are pri- est level of data available for each source so as to aid in marily designed to provide the user the emissions from identifying key (major) sources. Each data source and the one person's air travel, principally associated with aircraft methods that are used should be clearly documented by usage. In contrast, the inventory produced using this the developers of the inventory. Guidebook is designed to capture all of the emissions from sources at an airport (not just single flights), with 14. Question: Should multiple formats be used to report aircraft likely to be the dominant source. The results the airport inventory? of an airport inventory are not easily compared with Answer: This depends on the purpose of the inventory. those of an online calculator unless the airport inven- The Guidebook recommends that the documentation tory can identify the average flight distance of flights at specifying the inventory note the methods and sources an airport. that are commensurate with the reporting format. Some airports may wish to report their emissions in a simple 11. Question: Why do online carbon calculators use a format whereas others may wish to use multiple formats. Radiative Forcing Index (RFI) and how do these relate For instance, if an airport chooses to report their inven- to the methods in the Guidebook? tory to TCR, the format for this registry must be used. However, to aid the airport in understanding and moni- Answer: Several online calculators employ an RFI to toring its emissions, the airport may choose to have an account for many of the unknowns about the effects of alternative planning format. aircraft emissions on climate change and some incorrectly use the RFI. The Guidebook does not recommend the use 15. Question: For aircraft emissions, the FAA AEDT/SAGE of an RFI for airport-related GHG inventories. Rather, data source presents current (historical) emissions. How similar to protocols for other industries, this Guidebook should I estimate future aircraft emissions? recommends that at a minimum, Level 1 inventories be prepared to show CO2 emissions. For the standard Level 2 Answer: Airports can estimate future emissions in a num- inventories, reflecting emissions of the six Kyoto GHGs, ber of ways. First, Aircraft Methods 1 and 2 are available to
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52 airports for use if forecasts of fuel dispensed are available. the Guidebook as the preferred Aircraft Method 3. The Many airports increase existing fuel-dispensed quantities fact that the mixing height is different from the 3,000-ft in proportion to the change in aircraft operations over height does not affect the GHG inventories since the total time. Some airports have aviation activity forecasts that AEDT/SAGE GHG data (above and below 3,000 ft) for would enable use of Method 2 for future years. Although an airport still represents the total GHG emissions from Methods 1 and 2 are not preferred, they are acceptable aircraft. In evaluating criteria pollutants, some airports use alternative methods. the local mixing height in their modeling as recommended by USEPA and state air agencies. Therefore, should an 16. Question: For aircraft emissions, the FAA AEDT/SAGE airport choose to generate a Level 2 or Level 3 pollutant data source presents emissions assuming the mixing evaluation reflecting criteria pollutants using a different height is 3,000 ft. At my airport, the mixing height is mixing height, these airports should note the different as- not 3,000 ft. Does this matter? And if so, where? sumptions in the documentation. This would not affect Answer: No. The FAA source is provided to enable all the total emissions for aircraft, but would affect the subset airports to have access to a common source of aircraft of total emissions reported for "ground to 3,000 ft" and emissions using the IPCC Tier 3 method, referred to in "above 3,000 ft."