National Academies Press: OpenBook

Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories (2009)

Chapter: Chapter 2 - Inventory Development Considerations

« Previous: Chapter 1 - Introduction and Background
Page 12
Suggested Citation:"Chapter 2 - Inventory Development Considerations." National Academies of Sciences, Engineering, and Medicine. 2009. Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories. Washington, DC: The National Academies Press. doi: 10.17226/14225.
×
Page 12
Page 13
Suggested Citation:"Chapter 2 - Inventory Development Considerations." National Academies of Sciences, Engineering, and Medicine. 2009. Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories. Washington, DC: The National Academies Press. doi: 10.17226/14225.
×
Page 13
Page 14
Suggested Citation:"Chapter 2 - Inventory Development Considerations." National Academies of Sciences, Engineering, and Medicine. 2009. Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories. Washington, DC: The National Academies Press. doi: 10.17226/14225.
×
Page 14
Page 15
Suggested Citation:"Chapter 2 - Inventory Development Considerations." National Academies of Sciences, Engineering, and Medicine. 2009. Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories. Washington, DC: The National Academies Press. doi: 10.17226/14225.
×
Page 15
Page 16
Suggested Citation:"Chapter 2 - Inventory Development Considerations." National Academies of Sciences, Engineering, and Medicine. 2009. Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories. Washington, DC: The National Academies Press. doi: 10.17226/14225.
×
Page 16
Page 17
Suggested Citation:"Chapter 2 - Inventory Development Considerations." National Academies of Sciences, Engineering, and Medicine. 2009. Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories. Washington, DC: The National Academies Press. doi: 10.17226/14225.
×
Page 17
Page 18
Suggested Citation:"Chapter 2 - Inventory Development Considerations." National Academies of Sciences, Engineering, and Medicine. 2009. Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories. Washington, DC: The National Academies Press. doi: 10.17226/14225.
×
Page 18

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

12 This chapter provides all of the protocol considerations to develop an airport GHG emissions inventory. Each sec- tion in this chapter serves to provide guidance on specific aspects of an inventory (e.g., source categorizations, geo- graphic boundaries, etc.). They essentially provide instruc- tions on how to set-up an inventory. In contrast, Chapter 3 provides all of the calculation methods to complete the in- ventory. An overview of the procedure is shown in Figure 2-1 and is reflected in the ensuing sections. The steps in Figure 2-1 are shown serially in an attempt to methodically explain the process. However, it is expected that these steps may be followed in parallel under many cases to allow more efficient development of an inventory. As invento- ries are being prepared due to local influences, each airport operator should determine the best use of this guidance mate- rial based on their project needs and the data available. cussed in Section 1.4, the following four categories are rea- sons for developing an airport GHG inventory: 1. Climate change initiatives—GHG reduction goals, 2. Environmental management and sustainability programs, 3. Disclosure of project/action effects, and 4. Future regulations. For the first category (climate change initiatives—GHG reduction goals), all sources that generate GHGs and are used or operated at the airport, including those owned by the air- port operator (e.g., infrastructure items), as well as those that are influenced by the airport (e.g., aircraft) should be included in the inventory. This allows a comprehensive accounting of all sources, which is typically desired in a climate action plan. The inventory can be used to identify major sources and track the emissions of these sources over time. As a result, all of the sources listed later in Chapter 3 would ideally be included in an inventory developed for this reason. The next two categories (environmental management and sustainability programs and disclosure of project/action effects) represent subsets of the climate action initiatives in terms of source coverage. In these two categories, only the affected sources are included in the inventory since the pur- pose is to monitor changes in GHG emissions associated with a project or action. For example, in a state NEPA-like inven- tory, such as the previous example of a runway extension, only the sources affected by the extension are included in the inventory. These could include construction equipment to build the extension, aircraft ground movement, and energy for runway lighting. For a sustainability project involving fuel conservation, just the airport infrastructure energy use (possi- bly electricity use) could be assessed depending on the specifics of the project. Often, the goals of such projects are to show differences in emissions caused by the projects. That is, the goals are to determine the differences between action (build) and no-action (no-build) cases to show the adverse or bene- C H A P T E R 2 Inventory Development Considerations Although this Guidebook provides instructions on developing a GHG inventory, each airport opera- tor should determine the most efficient use of the information based on their own needs and data. In large part, this chapter is based on the background infor- mation provided in Appendix E. As such, that appendix should be reviewed for any additional information or clarifications on the guidance provided herein. 2.1 Purpose of the Inventory The first step in the inventory development procedure is to determine the purpose of the inventory. This will aid in defin- ing the breadth of sources to be considered. It is the respon- sibility of the inventory developers to make sure they under- stand the purpose for generating inventories such that they will know which sources to include in the inventory. As dis-

13 2.2.1 Traditional Criteria Pollutant Inventory Boundaries Most airport inventories that exclusively address criteria pollutants reflect emissions of sources within the airport fenceline (exceptions occur for inventories prepared under NEPA or state NEPA equivalents where a project affecting emissions outside the fenceline typically quantifies the emis- sions outside the fenceline), except for aircraft, which are lim- ited to the operations in the landing and takeoff cycle (LTO, generally operations under 3,000 ft). Emissions are typically reported by pollutant and match the source categories listed in the FAA’s Aviation Environmental Design Tool (AEDT)/ Emissions and Dispersion Modeling System (EDMS) (FAAa 2007), as follows: • Aircraft (in the landing and takeoff cycle) and APU, • Ground support equipment (GSE), • Stationary sources, • Parking facilities and roadways (also called ground access vehicles or GAV) • Training fires, and • Construction activities. In preparing traditional criteria pollutant inventories, little consideration is given to who owns the sources or controls these emissions. 2.2.2 Greenhouse Gas Inventory Boundaries During the last decade, the consideration of GHG inven- tories has evolved to contain a step that requires a clear iden- tification of the boundaries of the inventory. USEPA and World Resources Institute (WRI) along with World Business Council for Sustainable Development (WBCSD) guidance suggest that the following be considered when establishing the boundaries (USEPAa 2005 and WRI 2004): • Organizational structure—Is determined as reflected by control through ownership, legal agreements, joint ven- tures, etc. In the case of an airport, most airports are owned and operated by either: (1.) a city department, (2.) a county department, (3.) a state office, or (4.) an authority or port dis- trict. In preparing an inventory, the airport operator should consider how the inventory prepared for airport-related activities would be integrated into a broader organizational ficial environmental cost of the action. Therefore, only the af- fected sources in Chapter 3 would be considered when devel- oping inventories under these two categories. It is up to the inventory developer to fully identify the affected sources for each project. A GHG inventory developed in anticipation of future reg- ulation could require coverage of all sources (as with a climate action initiative) or a subset (as with the environmental man- agement and sustainability programs and disclosure of project/ action effects). This depends on the future regulation(s) for which an inventory developer is preparing. Although the focus is mainly on regulations requiring mandatory reporting of GHG inventories, this Guidebook can also be helpful for other types of regulations that may not explicitly state the need for GHG inventories. The methods for quantifying GHG emis- sions that are presented in this Guidebook should be applica- ble to all of these regulations. 2.2 Identification of the Ownership and Control Boundaries In preparing a GHG inventory, consideration must be given to boundaries of the inventory and the sources reflected in that inventory. Most often, the boundaries begin with issues of ownership and control. Whenever applicable, WRI protocols for source boundary and direct versus indirect emissions guidelines should be followed for consistency. Purpose of the Inventory Identification of the Ownership and Control Boundaries Identification of Sources and Pollutants Ownership and Influence Categorizations Geographic Boundaries Calculate Emissions Calculate CO2 Equivalencies Chapter 2 Chapter 3 Data Availability Reporting Units for Pollutants Figure 2-1. Overall inventory development procedure.

14 inventory (i.e., the airport division’s inventory of a city- owned airport relative to other activities of a city). • Operational boundary—Once an entity has determined its organizational boundaries in terms of the operations that it owns and controls, it then sets its operational bound- aries. This involves identifying the emissions associated with its operations and categorizing them either as Scope 1 (direct), Scope 2 (indirect), or Scope 3 (indirect and optional) emissions. – Scope 1/direct emissions are from sources that are owned and controlled by the reporting entity (e.g., on-airport emissions from combustion in owned and controlled boilers, furnaces, vehicles, etc.). For an airport, the Scope 1 emissions would be those associated with fuel powering vehicles owned and operated by the airport entity, as well as stationary sources owned and operated by that entity. For instance, an airport owns snow re- moval equipment and ground vehicles that burn fuel to service the airport, as well as the airport heating system or generators that may burn heating oil. – Scope 2/indirect emissions are those from the genera- tion of purchased electricity consumed by the entity. This would represent the electricity acquired to power air- port facilities. Tenant-purchased electricity would not be Scope 2, but Scope 3. – Scope 3/indirect and optional emissions are a conse- quence of the activities of the entity, but occur at sources owned and controlled by another party. Scope 3 would be the largest quantity of emissions at an airport, be- cause they would include aircraft-related emissions, emissions 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. Indirect and direct emissions as advocated by USEPA are similar to the Scope 1 and Scope 2 emissions noted by WRI, whereas WRI Scope 3 emissions are the emissions that USEPA considers optional. For the remainder of this docu- ment, the terms Scope 1, Scope 2, and Scope 3 are used to simplify the discussion. ICLEI has prepared draft guidance to international local governments concerning the preparation of GHG inventories (ICLEIb 2008). Within the ICLEI guidance, in addition to or- ganizational structure and operational boundary, there is a third element to be considered in inventories: geopolitical boundaries. The geopolitical boundaries ensure that the in- ventory reflects the accounting of emissions in a way that is “policy relevant,” meaning that the inventory is structured to reflect sources that can be affected through policies of the local government. In this way, the ICLEI guidance differenti- ates between the following two types of inventories: It should be noted that the adoption of the community- scale approach and the use of the Scope 1, 2, and 3 definitions reflect, in part, a desire to stay consistent with these protocols from ICLEI and WRI. Although the Guidebook has adopted these approaches, airport inventories could potentially be developed in other ways (e.g., focusing on just the airport- owned sources, no categorization of sources, etc.). The inven- tory developer should be cognizant of these other possibilities to properly address concerns that may be raised regarding the approaches recommended in this Guidebook. • Government operations analysis considers Scope 1, 2, and 3, where Scope 3 only includes emissions over which the government exerts significant control or influence. In this case, generally only the emissions from sources owned and controlled by the airport governmental entity would be re- flected. Thus, aircraft sources would be omitted, unless the airport governmental entity owns and operates aircraft, as is sometimes the case of State Aviation Divisions. • Community-scale analysis also considers Scope 1, 2, and 3 but seeks to reflect geopolitical boundaries. In the airport context, this inventory could reflect the inclusion of airport tenant activities that would include airline and aircraft op- erations. In the community context, ICLEI provides guid- ance for the inclusion of an airport’s emissions if the air- port is not physically located within the city boundaries, where many residents of the city use the airport. The preferred method for airports recommended by this Guidebook is the preparation of inventories that reflect the community-scale analysis when preparing inventories for climate action plans. This is recommended to ensure consis- tency among airports, as the inventories for some airports are likely to be prepared by entities that participate in ICLEI or choose to register their emissions. Alternatively, if data are not available to enable the community-scale approach, the government operations analysis could be undertaken, with the inventory noting the deficiencies in available data. This Guidebook recommends that the traditional criteria pollutant format when applied to GHGs be recast using ownership and control reporting, where possible, for the NEPA-like evalua- tions and sustainability projects so as to enable GHG pollutants and criteria pollutants to be documented using a common format. Such a reformatting would not require additional analysis, and would enable a direct comparison between climate action plans and NEPA-like/sustainability project evaluations. If possible, an airport GHG inventory should follow ICLEI’s community-scale analysis reflecting the emis- sions by both airport- and tenant-owned sources.

2.3 Identification of Sources and Pollutants As suggested previously, the sources to be included in an airport GHG inventory will depend on the purpose of the inventory. If the purpose is a climate action plan, then— typically—all sources under the ownership and control of the airport operator are identified, as well as those owned by ten- ants. This is in keeping with the community approach from ICLEI’s boundary guidance. For NEPA-like project evalua- tions and sustainability projects, the airport operator typi- cally has the flexibility to narrow the sources inventoried to those affected by the project. The starting point for identifying the affected airport sources is to first list all six sources that have traditionally been cited for criteria gases and are consistent with the sources listed in the FAA’s AEDT/EDMS (FAAa 2007): (1.) aircraft (in the LTO cycle) and APU, (2.) GSE, (3.) stationary sources, (4.) parking facilities and roadways (also represented by GAV), (5.) train- ing fires, and (6.) construction activities. Each of these sources should be considered relative to the party who owns/controls the source. For example, airport operators would be likely to focus on airport-owned GSE, stationary sources, fire training, and construction. Only if an airport operator owns and controls aircraft would aircraft and APU emissions be associated with the airport operator. Rather, aircraft emissions generally would be associated with tenants, along with APUs, GSE, tenant-based GAVs, etc. Although this list is comprehensive overall, it is not spe- cific to every source at an airport. For example, the station- ary sources category covers a wide range of specific sources (e.g., boiler/heater, maintenance activities, engine tests, etc.) that could be listed individually depending on the needs of the airport operator or project. Further, for purposes of a GHG inventory, the stationary sources would also include ac- counting for electrical use (also called facility power). To pro- vide consistency to both the criteria pollutant inventories and airport GHG inventories, the Guidebook recommends that the above six categories be preserved. Airports would have the flexibility to include more specific sources under those cate- gories as exemplified in Table 2-1. Two additional cate- gories—waste management (recycling) and other (a catch-all category for emissions unique to an airport)—are included in Table 2-1 that are not generally found in criteria pollutant inventories. Once the sources are identified, the availability of data and resources will need to be assessed to determine the pol- lutants to be accounted for in the inventory. Based on guid- ance provided by WRI and IPCC, as well as experience airport operators have gained from developing GHG inventories, it is recommended that the following levels of pollutant cate- gories be used as a guide: • Level 1 inventory that only considers CO2; • Level 2 inventory (recommended) that considers six Kyoto pollutants (CO2, CH4, N2O, SF6, HFC, and PFC)—primary pollutants; and • Level 3 inventory that considers all pollutants including the six Kyoto pollutants, precursors and any others exerting a GHG effect. At a minimum, CO2 emissions (Level 1) must be quanti- fied to form a GHG inventory. If resources and data allow, all attempts should be made to quantify the Kyoto pollutants (the primary pollutants) called out in Level 2. Although six pollutants are noted, it is likely that a Level 2 inventory would be dominated by CO2 with lesser levels of CH4 and N2O. In part because of data availability and understanding of these emissions, the focus for Level 2 is usually on these three pol- lutants. This level is consistent with GHG inventory protocols identified by IPCC, WRI, ICLEI, and TCR. As such, a Level 2 inventory is the recommended level for an airport inven- tory. Level 3 is an alternate, and includes both precursors and 15 Source Category Specific Source Ground (reflecting taxi-idle, delay) Ground to 3,000 ft (reflecting takeoff, climbout, and approach) Above 3,000 ft Aircraft and APU Aircraft engine tests GSE Emissions may be reported in aggregate, but data collection requires knowledge of different types of GSE used by airport operators (snow removal, maintenance equipment, etc.) versus tenants (baggage tractors, belt loaders, cabin service trucks, etc.) Vehicles transporting passengers (private autos, taxis, vans, shuttles, rental cars, etc.), and vehicles using airport parking Vehicles transporting airport and tenant employees, including vehicles in employee parking lots Vehicles transporting cargo Parking Facilities and Roadways (GAV) Airport-owned vehicles Airport facility boilers, heaters, and generators Fuels used by food concessions Maintenance activities Stationary Sources/Facility Power Electrical consumption Training Fires Fuel usage for planned training activities Construction Vehicles consuming fuels during the construction process Waste Management Waste recycled, waste landfilled, etc. Other All other sources such as local on- airport companies with industrial processes, farming activities, etc. Table 2-1. Example of inventory categories showing specific sources.

16 any other pollutants (e.g., other halogenated compounds). Level 3 is geared toward satisfying scientific needs for a com- prehensive accounting of all GHG effects while recognizing that Levels 1 and 2 generally capture the bulk of GHG emis- sions. Background information on all of these pollutants can be found in Appendices B through D. Reporting at either Levels 2 or 3 would allow the highest assessment of an airport’s carbon footprint and would be the most beneficial to the scientific community. Levels 1 and 2 are likely to be the most frequently prepared inventory levels. In- ventory Level 3 would be the most detailed and also the most costly for the airport operator to prepare. Levels 2 and 3 serve as loose guidelines since it would also be beneficial to report a set of pollutants (in addition to CO2) that partially cover these levels. For example, an airport may choose to report CO2, CH4, and N2O but not have the data and/or resources to report the halogenated compounds (SF6, HFC, and PFC) in Level 2. In this case, the reporting could be characterized as a partial Level 2. Similarly, partial reporting can be done for Level 3 or a combination of Level 2 and 3 (e.g., reporting CO2, CH4, and N2O which are common to Levels 2 and 3, while also reporting NOx from Level 3). irrespective of the purpose of the inventory. For example, whether an inventory is developed for a registry or as part of a NEPA-like study, the preferred approach should always include this ownership and control layer, as it provides clarity in identifying the party/parties that can control those emissions. Table 2-2 shows an example of the categorization layer (i.e., “owning entity”) in the first two columns (owning entity and source). A third column is provided for informa- tion purposes to relate these sources to the previously iden- tified Scopes 1, 2, and 3. At an airport, the following three categories relate to ownership and control: • Airport operator owned and controlled, • Tenant owned and controlled (tenants include airlines, gov- ernment, concessionaires, aircraft operators, fixed-based operators, etc.), and • Public owned and controlled. For those inventories that will be used to guide and mea- sure the success of an emission reduction program, this layer provides sufficient transparency of the evolution of emissions over time to the public. As an option, additional layers could be added to point out the level of influence that non-owning entities have on certain sources. Such additions are at the dis- cretion of the airport operator. As explained in Appendix E, entities that do not own but exert influence on sources can (and often should) be acknowledged for the emissions (or reduc- tions of emissions) from these sources. As indicated previously, the allocation of emissions based on influence is outside the scope of this Guidebook. Therefore, although we note that the influence can be acknowledged, there is currently no guid- ance available to help quantify the allocations. The underlying implication regarding this subject is that airports can have varying degrees of influence over sources they do not own. In general, all airport tenants are affected by the assets owned and controlled by the airport operator in some way, even if loosely through airport policies. As such, the airport operator may influence each source at the airport to varying degrees, and may also be able to claim recognition/ credit for emissions reductions from those sources as well (again, to varying degrees). In keeping with the guidance provided by WRI and as adopted by a variety of other organizations, as an option, categorization layers for the direct and indirect nature of emissions and their sources (classified as Scope 1, 2, or 3) also could be included. If the inventory is reported to TCR, this categorizing layer would provide consistency with the registry since it also uses these categories. To help efficiently use airport resources, a screening process could be employed to identify the major sources. An ownership and control categorization layer should be developed for all inventories, irrespec- tive of the purpose of the inventory. Level 1 (only CO2 emissions) is the minimum for a GHG inventory, but Level 2 or higher is preferred. As part of the data collection and resource issues, a screening process could be employed to determine the significant sources. This would be useful for many airports that have limited re- sources and need guidance to determine which sources to ex- clude. The protocols from both IPCC and WRI promote the use of such approaches. Although WRI does not promote quanti- tative criteria at this time, IPCC suggests a 95% cutoff point such that sources accounting for 95% of emissions should be sufficient to report in an inventory (IPCC 2006). The 95% level can be determined from examining prior inventories. CCAR (2008) also employs the 95% criterion, referring to 5% as “de minimis.” This is also supported by TCR (TCRa 2008). How- ever, if data are available, and the effort to report the remaining 5% is reasonable, airport operators should consider including these de minimis sources in the inventory for completeness. 2.4 Ownership and Influence Categorizations All airport GHG emissions inventories should have an ownership/control categorization layer. This should be done

Unlike the health effects associated with criteria gases, GHG effects are global in nature and, hence, it does not matter where those emissions occur— ALL of the emissions must be accounted for. 17 As an option, the WRI scope categories could be specified to allow a better understanding of the direct and indirect nature of the emissions. 2.5 Geographic Boundaries Since the effect of GHG emissions is global in nature, there are no “airport boundaries” in a true geographic sense as there are for criteria pollutants. The emissions from airport sources identified in Section 2.4 should be accounted for irre- spective of where they occur. This means that in addition to accounting for emissions that occur on airport property (e.g., GSE, stationary sources, etc.), emissions from sources owned or influenced by the airport should also be included whether or not they occur on airport property or near the airport (e.g., as is the case for autos traveling to and from the airport). Judgment is required for some sources as to the extent of the airport’s level of influence for purposes of achiev- ing a policy-relevant inventory. All of the sources listed in Sec- tion 2.4, however, are considered to be either controlled or in- fluenced by the airport. Designating sources by ownership and control is recommended to further assist with the inventory. Owning/Controlling Entity Source Scope Aircraft (only aircraft owned by the airport operator; a few airport operators fly aircraft that they own ) Scope 1 APU Scope 1 GSE Scope 1 GAV Scope 1 Stationary Sources Scope 1 (electricity consum ed in Scope 2) Fire Training Scope 1 Construction Scope 1 Waste Recy cling Scope 3 Airport Operator Other Scope 1/2/3 Aircraft Scope 3 APU Scope 3 GSE Scope 3 GAV Scope 3 Stationary Sources Scope 3 Construction Scope 3 Waste Recy cling Scope 3 Tenant (includes airlines, governm ent, concessionaires, aircraft operators, fixed-based operators, etc.) Other Scope 3 Public GAV Scope 3 Table 2-2. Example of ownership categorization layer. For aircraft, it is recommended that emissions from the full flight (gate-to-gate) should be accounted for if sufficient in- formation is available. Volume 2, Chapter 3 of the IPCC (2006) guidelines indicate that aircraft GHG emissions should be attributed to the departure country. This Guidebook recog- nizes that many approaches are available—ranging from not including aircraft in the inventory to including both the arrival and departure-related emissions in each airport’s inventory. However, in keeping with the IPCC international protocol, this Guidebook recommends that each flight’s emissions be attributed to the departure airport only. If all airports take this approach, this will provide consistency with each airport’s inventory, avoid double counting, and allow individual air- port inventories to be compared with, or aggregated to, larger scale inventories such as state inventories or USEPA’s na- tional inventory. This approach is the preferred approach for aircraft, because—if uniformly applied—it avoids double counting. Where possible, aircraft emissions should be assessed by individual legs of a flight rather than the departure and final destination of multi-leg flights. For instance, emissions from a flight that leaves JFK to fly to ORD, then to DEN, and then to SFO, should be attributed as shown below and in Figure 2-2. • Emissions of flight from JFK to ORD should be attributed to JFK, • Emissions of flight from ORD to DEN should be attrib- uted to ORD, and • Emissions of flight from DEN to SFO should be attributed to DEN.

As an option, the flights (and hence, emissions) can be further categorized into domestic and international flights, as follows: • A domestic flight is from a U.S. airport to another U.S. airport. • An international flight is from a U.S. airport to a non-U.S. airport; for non-U.S. airports, an international flight is from a non-U.S. airport to a U.S. airport. It should be noted that when all of a flight’s emissions are attributed to the departure airport, it results in a geograph- ically distorting effect—the location of the point of actual emissions do not align with the geographic location of the air- port as they do with the traditional assessment of criteria pol- lutants within the LTO cycle. Also, the total departure flight emissions attributed to an airport could be different than the total emissions derived from summing half the emissions from arriving flights and half the emissions from departing flights. Notwithstanding the technical difficulties (e.g., poten- tial for overlaps with other airport inventories) associated with such an approach, this could at least geographically “center” the emissions at the airport. These issues need to be carefully considered, especially as policies are made regarding attribu- tion of GHG emissions to airports. Similar concerns can also be raised for GAVs, construction equipment, etc., that oper- ate outside of the airport property. For publicly owned and controlled GAV travel, emissions resulting from full round-trips should be captured. An exam- ple of a round-trip would be for a passenger who travels from his/her home to the airport, and upon completion of the air travel, returns home. Thus, for GAVs, the emissions from ori- gin to the airport and the return segment should be quanti- fied even if a passenger was dropped off at the airport. This could also apply to airport operator and tenant employees who travel to or from the airport, as well as the movement of con- struction equipment. Ideally, multipurpose trips (e.g., involv- ing travel to a store before returning to the origin) should only account for the direct distance from the origin to the airport and vice versa. Such side trips should not be included in the in- ventory as they are not a part of the purpose for the airport trip. However, if the side trips are already embedded as part of the data available (e.g., total VMT data), it may be difficult—and resource intensive—to attempt to remove the side-trip contri- butions. Therefore, side trips could be left in the data and prop- erly documented to reflect this, especially since the overall effect on the inventory will likely be small. 2.6 Data Availability As with any new evaluation process, an airport operator may not have data collected in a format and depth necessary to undertake some of the preferred approaches to quantify- ing emissions from a specific source. Alternatively, less de- tailed data may be available requiring the use of alternative quantification approaches. Additionally, many airports may not have any data concerning a specific source, particularly those associated with a tenant. The Guidebook recommends that the documentation accompanying the inventory clearly identify the data that were available (and their source), how the data were used, and any issues associated with that data. Such documentation should strive for the greatest clarity and ability to replicate the results outside of the report. Depend- ing on data availability, airport operators may not be able to perform any quantification of emissions for certain sources. All such cases should be clearly documented. 2.7 Reporting Units for Pollutants GHG emissions are typically reported in metric tons. How- ever, depending on the units of the source data (e.g., emission factors), emissions calculations can directly result in either English (e.g., lbs) or metric (e.g., g, kg) units. These should all be converted to a common unit, preferably the metric ton. Using this common unit allows easy reviews and compar- isons with other inventories. The following conversions may be useful in preparing an inventory: • 1 lb = 0.0004536 metric ton, • 1 g = .000001 metric ton, • 1 kg = 0.001 metric ton, • 1 Mg = 1 metric ton, • 1 Gg = 1,000 metric tons, and • 1 Tg = 1,000,000 metric tons. 18 DEN Emissions ORD Emissions JFK Emissions JFK ORD DENSFO Figure 2-2. Attribution of aircraft emissions to the departure airport based on single flight legs. All of the emissions from aircraft flights are allo- cated to the departure airport.

Next: Chapter 3 - Emissions Calculations and Application of CO2 Equivalencies »
Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB’s Airport Cooperative Research Program (ACRP) Report 11: Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories explores a framework for identifying and quantifying specific components of airport contributions to greenhouse gas emissions (GHG). The report is designed to help airport operators and others to prepare an airport-specific inventory of greenhouse gas emissions.

Appendices A through F to ACRP Report 11 were published online as ACRP Web-Only Document 2. The appendices titles are as follows:

Appendix A-Reasons for Developing GHG Inventories

Appendix B-Emissions and Sources

Appendix C-Methods for Calculating GHG Emissions

Appendix D-Methods for Calculating CO2 Equivalencies

Appendix E-Inventory Development Protocols

Appendix F-Approaches Used in Airport Inventories Prepared to Date

An ACRP Impacts on Practice related to ACRP Report 11 is available.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!