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4 As communities in the United States come to terms with the local and global impacts of green- house gas (GHG) emissions on the environment, the climate, and public health, the importance of identifying feasible and practical measures for reducing these emissions becomes greater. According to the Fourth National Climate Assessment, Volume II: Impacts, Risks, and Adapta- tion in the United States (USGCRP, 2018), the efforts of government agencies, private industry, and local communities to reduce GHG emissions have intensified and expanded but âdo not yet approach the scale considered necessary to avoid substantial damages to the economy, envi- ronment, and human health over the coming decades.â Published every four years by the U.S. Global Change Research Program (USGCRP), this congressionally mandated report also finds that, in addition to directly lowering GHG emissions, âmitigation . . . presents opportunities for additional benefits that are often more immediate and localized, such as improving local air quality and economies through investments in infrastructureâ (USGCRP, 2018). Airports, both nationally and abroad, are uniquely positioned to implement and advance these GHG reduction-related actions and practices: â¢ As the crossroads of air transportation, airports are complex spaces that provide critical tech- nical and operational support to aircraft, airlines, and their associated infrastructure. â¢ As the access point to air travel for billions of passengers around the world, airports provide an immense array of logistical services necessary for moving people and their goods on and off airplanes. â¢ As a focal point for the operations of local government, airports offer a unique opportunity to communicate leadership in public policy to the public in a highly visible place. â¢ And, as increasingly social spaces, airports are developing auxiliary services and adding more revenue-generating amenities to accommodate and attract the traveling public. This dynamic confluence of transport, commerce, and hospitality requires significant and reliable energy to operate safely and to run smoothly. GHG emissions resulting from these extensive energy demands are a significant and material source of overall emissions. However, this broad range of airport energy demands also provides an array of opportunities for determin- ing best practices for reducing GHG emissions. Whether by replacing fossil fuels with alternative power sources or by developing carbon offsetting programs or economic initiatives for GHG reduction measures, airports offer a specific setting in which the merger of improved technolo- gies, operational procedures, funding support, and public awareness can catalyze the successful implementation of GHG emission reduction practices. This synthesis examines a wide variety of GHG reduction practices implemented at U.S. airports that can help achieve this balance. Using ACRP Report 56: Handbook for Considering Practical Greenhouse Gas Emission Reduction Strategies for Airports (Lemaster and Vigilante, 2011) as a baseline, this synthesis describes the specific outcomes and practical considerations C H A P T E R 1 Introduction
Introduction 5 of establishing GHG reduction initiatives at a diverse range of airports across the United States. By specifically detailing 17 case examples of practices identified in ACRP Report 56 and by con- sidering a broad spectrum of additional data regarding GHG reduction strategies put into place following the publication of ACRP Report 56 in 2011, this report attempts to provide timely, realistic, and useful data for U.S. airports currently considering similar initiatives. 1.1 Airport Greenhouse Gas Emission Sources The Intergovernmental Panel on Climate Change (IPCC) estimates that 2% of global anthropogenic carbon emissions come from aircraft, with total emissions in 2017 estimated at 897 million tonnes (International Air Transport Association, 2018). In 2017, airline traffic at U.S. airports reached an all-time high of 965 million scheduled passengers, a 3.4% increase over the previous record high reached in 2016 (Bureau of Transportation Statistics, 2018). While this growth reflects the demand for aviation, the consequential increases in energy use and fuel consumption have direct implications for GHG emission levels. Global aviation has demonstrated that passenger growth and GHG emission rates can be decoupled, as evidenced by a growth in passenger numbers at an average rate of 7.5% over the past two years compared with GHG emissions growth of approximately 5% during the same period (GreenAir, 2018). This has been accomplished through the advancement of technologies, broader funding initiatives and incentives, and the creation of innovative tools and programs. However, for the aviation industry to meet both the demand for increased air travel and the demand to reduce its carbon footprint, a greater efficiency in emissions per passenger will be necessary and the success of carbon offsetting and the wider adoption of sustainable aviation fuels will need to be realized. Airports are also growing to accommodate the increased demand for airport travel by expand- ing their infrastructure and facilitating passenger movement from their ground transportation mode to the aircraft. As the key link between planes, passengers, cargo, ground transportation, and a multitude of land-based services, airports must adapt to this growth by increasing their capacity while simultaneously limiting their environmental impacts (Scavuzzi, 2017). Yet a survey of 11 U.S. airports that prepared GHG inventories indicates that airports control less than 10% of aviation emissions, with the predominance produced by aircraft operation and passengers transiting to and from the airport (Cooper et al., 2015). Airport GHG emissions are caused by the use of fossil fuel for electricity and heating, gasoline and diesel fuel for airport ground transportation vehicles and ground support equipment (GSE), and jet fuel for take-off and landing cycles of aircraft and for auxiliary power units (APUs) that power aircraft at the gate, as well as other sources (FAA, 2017). Greenhouse gases emitted at airports include CO2 (carbon dioxide), CH4 (methane), NOx (nitrogen oxides), SO2 (sulfur dioxide), and fluorinated gases, which make up the largest share of GHGs. Airport GHG emission sources can be categorized by source and location. The GHG protocol defines emissions as direct or indirect, and it classifies emission sources into three categories: â¢ Scope 1: direct emissions from airport-owned or -controlled sources â¢ Scope 2: indirect emissions from purchased electricity, heat, or steam â¢ Scope 3: indirect emissions from other sources related to the activities of the airport The Airport Carbon Accreditation Program, a carbon benchmarking and reporting frame- work developed by Airports Council International (ACI) specifically for airports, uses the inter- nationally accepted GHG protocol to categorize GHG emissions. Figure 1-1 illustrates airport emission sources and the applicable scope for each. Table 1-1 provides the same information but in list format. The numbers in Table 1-1 identify the sources illustrated in Figure 1-1.
6 Airport Greenhouse Gas Reduction Efforts Airport emissions can also be categorized by location as terminal, airside, and landside. Figure 1-2 shows the distinctive locations of these categories. Although airports vary significantly in their overall energy use because of their function and the complexity of their spaces and operational characteristics, airport terminals are among the largest of all energy consuming buildings (Ahn and Cho, 2015). Terminals are large buildings that require a significant amount of electricity to power the lights, security systems, screens and visual displays, baggage systems, elevators and escalators, office spaces, and individual tenant needs (Baxter, Srisaeng, and Wild, 2018). Building energy use constitutes 10%â15% of an air- portâs annual budget, and lighting can account for up to 40% of an airport terminalâs electricity use (Lau, Stromgren, and Green, 2010). With large, open terminal spaces and passageways, and passengers and staff constantly moving through doors that open to outside air, temperature control is a continued energy draw. Airside energy use is dominated by aircraft and ground support equipment. Airside aircraft emissions that are accounted for in an airportâs GHG inventory are produced during landing and take-off (with a jurisdictional boundary of 3,000 feet above ground level), as well as during taxiing to and from the terminal; emissions produced from gate activities are also included in an airportâs GHG inventory. At airports that do not provide gate electrification equipment, aircraft also operate their APU while at the gate between arrival and departure. Where gate electrifica- tion equipment is available, electricity demand from the airside is increased. Similarly, GSE, such as baggage tugs and belt loaders, is conventionally powered by diesel engines, although many Source: Airport Carbon Accreditation, 2019. Figure 1-1. Source of airport emissions and applicable scope category.
Introduction 7 Scope 1 (Airport â Direct) Scope 2 (Airport â Indirect) Scope 3 (Other â Indirect) 01 - Vehicles/ground support equipment belonging to the airport 07 - Off-site electricity generation from: 08 - Aircraft landing 02 - On-site waste management A. Heating 09 - Aircraft taking off 03 - On-site waste water management B. Cooling 10 - Aircraft ground movements 04 - On-site power generation C. Lighting 11 - Auxiliary power units 05 - Firefighting exercises 12 - Third-party vehicles/ ground support equipment 06 - Boilers, furnaces 13 - Passenger travel to and from the airport 14 - Staff commute 15 - Off-site waste management 16 - Off-site water management 17 - Staff business travel Source: Airport Carbon Accreditation, 2019. Table 1-1. Sources of GHG emissions at airports. Source: Landrum & Brown et al., 2010. Figure 1-2. Airport emission locations.
8 Airport Greenhouse Gas Reduction Efforts airports are installing vehicle charging equipment that allows airlines to consider programming replacement of older diesel units with electric-powered ones. Other vehicles that operate on the airside, including aircraft tugs and fuel delivery vehicles, are currently fueled by diesel. The airport fleet operating airside may be fossil-fuel powered but there is the potential to convert some units to hybrid or electric in the future. In addition, electricity is required for radar and navigational aids (NAVAIDS), communications, and airfield lighting to ensure the safe and efficient operation of an airfield. Like airside energy, landside energy is also dominated by vehicle use; however, landside infra- structures do account for some of the electricity demand. A wide variety of off-airport vehicles (e.g., personal cars/trucks, taxi/rideshare, shuttle buses, and limousines) transport passengers to the airport to meet their flights. Transit by electrically powered subway and light rail or diesel trains and buses may be available. Airports may operate shuttle buses and conventional buses, powered by gas or diesel, to move passengers between terminals or to move passengers to and from remote parking areas. However, airports may also operate newer bus models that use alternative fuels such as compressed natural gas and electricity. In addition, parking garages and surface parking areas require electricity for lighting and administrator operations. Table 1-2, adapted from ACRP Report 11: Guidebook on Preparing Airport Greenhouse Gas Emissions Inven- tories (Kim et al., 2009), provides a sample airport emissions inventory. Regardless of the source, GHG emissions are a focal point for local and global environ- mental advocates. As airports address key community issuesâfor example, addressing aircraft noise through mitigation programs such as new flight patterns, the acquisition of buffer zones, and sound-proofing of affected residencesâGHG impacts from aviation have become a local priority. There is increasing pressure to consider not only whether activities meet regulatory standards but also whether they are socially acceptable (i.e., whether they have earned a social license to operate). These evolving perspectives reiterate the importance of airport engagement with local communities on a variety of projects, including the beneficial work implemented to improve local air quality and reduce GHGs. Further research indicates that airports can effectively communicate their efforts to stake- holders who are ever more aware of the potential impacts of energy consumption on the envi- ronment. âIn recent years, airport managers have made huge efforts to harmonize airport operation with environmental sustainability by minimizing the environmental impact, with energy conservation and energy efficiency as one of their pillarsâ (Baxter et al., 2018). New tech- nologies, supporting programs, and funding agencies are creating measurable and standardized pathways to reducing energy use, fuel consumption, and GHG emissions from terminal, airside, and landside airport operations. 1.2 ACRP Report 56: Handbook for Considering Practical Greenhouse Gas Emission Reduction Strategies for Airports Published in 2011, ACRP Report 56: Handbook for Considering Practical Greenhouse Gas Emis- sion Reduction Strategies for Airports (Lemaster and Vigilante, 2011) serves as a starting point for assessing lessons learned from airport greenhouse gas reduction efforts. ACRP Report 56 represents a comprehensive reference for airport operators to use to identify, evaluate, prioritize, and implement practical, low-cost GHG reduction strategies. Among the resources it contains is a list of 125 practices, grouped into various categories, and a decision- making tool called AirportGEAR that can help airport operators select and prioritize strategies given their local climate and operational conditions.
Introduction 9 User Source/Category Scope CO2 Metric Tons/Year % of Source in User Category % of Total Airport Operator Owned/Controlled Stationary facilities â purchased facility power 2 30,000 51.7% 1.2% Stationary facilities â natural gas 1 10,000 17.2% 0.4% Ground support equipment/airport fleet 1 3,000 5.2% 0.1% Ground access vehicles (public vehicles on airport roads) 3 15,000 25.9% 0.6% TOTAL Airport Owned/Controlled 58,000 100% 2.3% Airline, Aircraft Operator, or Tenant Owned/Controlled Aircraft 3 Ground 3 140,000 6.2% 5.5% Ground to 3,000 ft 3 207,000 9.2% 8.1% Above 3,000 ft 3 1,890,000 84.1% 74.1% Aircraft Total 3 2,237,000 99.5% 87.7% Ground support equipment 3 6,540 0.3% 0.3% Ground access vehicles 3 1,270 0.1% 0.1% Stationary sources/facility power 3 3,000 0.1% 0.1% TOTAL Airline, Aircraft Operator, Tenant 2,247,810 100% 88.2% Public Owned/Controlled Public vehicles 3 175,000 71.72% 6.9% Taxis 3 34,000 13.93% 1.3% Vans/shuttles 3 23,000 9.3% 0.9% Light rail 3 Unknown na na Cargo trucks 3 12,000 4.92% 0.5% Total Public Owned/Controlled 3 244,000 100% 9.6% TOTAL 2,549,810 100% Waste Recycling 3 (852) GRAND TOTAL 2,548.958 Source: Kim et al., 2009. Note: na = not applicable. Table 1-2. Sample climate action plan emissions inventory.
10 Airport Greenhouse Gas Reduction Efforts A key point in ACRP Report 56 is the importance of establishing goals. Each airport operator investigating GHG reduction strategies is likely to have different priorities and emission reduction goals that will affect the process for selecting strategies. It is critical to establish clear goals early on so that planning and implementation can regularly be measured against the initial goals. The practices listed in ACRP Report 56 are organized under 12 categoriesâthe following 13 categories include the original 12 (with slight modifications for use in this synthesis) and a category added for use in this synthesis: â¢ Airfield Design and Operations (AF) â¢ Business Planning (BP) â¢ Construction (CN) â¢ Carbon Sequestration (CS) â¢ Carbon Offsets (CO) [New category added as part of this synthesis] â¢ Energy Management (EM) â¢ Ground Service Equipment (GS) â¢ Ground Transportation (GT) â¢ Materials and Embedded Energy (ME) â¢ Operations and Maintenance (OM) â¢ Performance Measurement (PM) â¢ Renewable Electricity and Fuels (RE/F) [Modified category for this synthesis] â¢ Refrigerants (RF) ACRP Report 56 also provides fact sheets on each of the practices that include a description, information on financing and implementation, and case studies. Some of this information is relevant to understanding lessons learned, and it has been included in this synthesis in Chap- ter 3, Case Examples. ACRP Report 56 remains a comprehensive resource for airport operators in understanding GHG emission reduction strategies, although changes in technology and costs of implementation suggest that an update would be warranted. As a supplement to ACRP Report 56, additional ACRP reports have been published that provide a more in-depth study of GHG reduction practices. These supplemental publications include the following: Greenhouse Gas Emissions â¢ ACRP Report 11: Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories, 2009 Energy Efficiency â¢ ACRP Synthesis 21: Airport Energy Efficiency and Cost Reduction, 2010 â¢ ACRP Web-Only Document 27: Methodology to Develop the Airport Terminal Building Energy Use Intensity Benchmarking Tool, 2016 LED Lighting â¢ ACRP Synthesis 35: Issues with Use of Airfield LED Light Fixtures, 2012 â¢ ACRP Report 148: LED Airfield Lighting System Operation and Maintenance, 2015 Ground Support Equipment â¢ ACRP Report 78: Airport Ground Support Equipment: Emission Reduction Strategies, Inventory, and Tutorial, 2012 â¢ ACRP Report 149: Improving Ground Support Equipment Operational Data for Airport Emissions Modeling, 2015
Introduction 11 Renewable Energy â¢ ACRP Synthesis 28: Investigating Safety Impacts of Energy Technologies on Airports and Aviation, 2010 â¢ ACRP Report 108: Guidebook for Energy Facilities Compatibility with Airports and Airspace, 2014 â¢ ACRP Report 141: Renewable Energy as an Airport Revenue Source, 2015 â¢ ACRP Report 151: Developing a Business Case for Renewable Energy at Airports, 2016 â¢ ACRP Synthesis 91: Microgrids and Their Application for Airports and Public Transit, 2018 Ground Transportation â¢ ACRP Synthesis 54: Electric Vehicle Charging Stations at Airport Parking Facilities, 2014 â¢ ACRP Synthesis 84: Transportation Network Companies: Challenges and Opportunities for Airport Operators, 2017 â¢ ACRP Synthesis 85: Alternative Fuels in Airport Fleets, 2017 Financing â¢ ACRP Synthesis 1: Innovative Finance and Alternative Sources of Revenue for Airports, 2007 â¢ ACRP Report 35: Planning for Off-Site Airport Terminals, 2010 â¢ ACRP Report 121: Innovative Revenue StrategiesâAn Airport Guide, 2016 â¢ ACRP Project 02-77: Revolving Funds for Sustainability Projects at Airports (report expected 2019) 1.3 Industry Progress to Date Airports are calculating their emissions and making commitments to reduce emissions on a per passenger basis (Airport Carbon Accreditation, n.d.). They are motivated by a variety of drivers, including the following: â¢ Reducing long-term operational costs by replacing older equipment that is costlier to main- tain and consumes more fuel with new technology â¢ Improving customer experience by using technology to increase convenience and reduce congestion while at the same time constraining emissions â¢ Maximizing opportunities associated with financial incentives, such as energy rebates, to reduce the upfront costs of cleaner-burning technology â¢ Increasing facility resilience to climate change by investing in new energy generation and storage equipment that can sustain airport operations even when the grid is down â¢ Achieving public policy commitments and coordinating with other government agencies in those efforts â¢ Demonstrating industry leadership by competing with other airports to push the limits of GHG strategy development â¢ Responding to stakeholder concerns and advancing relationships with interested parties including nearby communities by sharing information on planning and implementation â¢ Building a sustainability brand and expanding the airportâs influence beyond its own sources Turning these drivers into actual projects requires action by airport staff with knowledge, persistence, and creativity. The champions of these projects vary by airport and project; how- ever, buy-in from organizational and community leaders is critical to their success and enables projects to overcome the fundamental concerns of technological failure and cost overruns. Strong leadership allows small projects to grow and to develop into a more expansive vision for the airport.
12 Airport Greenhouse Gas Reduction Efforts Airports do not work in isolation to reduce emissions. Often they collaborate with local government to develop municipal or county climate plans; lessons learned are then shared with other departments within the local government, such as public works, that may be grappling with similar challenges. In one specific instance detailed in a case example for this report, air- port staff worked with wastewater treatment plant staff to learn how to prepare a solar feasibil- ity study, which resulted in the development of a major GHG reduction project. In addition, airports constantly receive information from tenants, customers, and colleagues in the industry about new technology and different ways of doing things. Some U.S. airports, such as Dallas-Fort Worth International (DFW) and San Diego Inter- national (SAN), have attained or are proposing to attain carbon neutralityâdemonstrating just how far airports can move toward GHG reduction. The strategies used by these airports are manifested in the GHG reduction practices identified in ACRP Report 56. Practices such as tech- nology adoption, funding, and program development have catalyzed airport progress in GHG reduction efforts, as summarized in Section 1.3.1. 1.3.1 Advancement of New Technologies â¢ Sustainable aviation fuels (SAFs), which result in up to an 80% reduction of CO2 emis- sions across their lifecycle, are being produced and used in commercial flights every day. As of November 2018, more than 150,000 commercial flights using SAFs have been performed (International Air Transport Association, 2019). â¢ Electrification of ground vehicle fleets, both on the airside and the landside, has been widely adopted. As of 2016, at least 22 airports have worked with their airline partners to convert to electric ground support equipment (eGSE) (National Renewable Energy Laboratory, 2017). At Seattle-Tacoma International Airport (SEA), the conversion of ground support equipment (GSE) from fossil fuel to electric power is projected to save $2.8 million in airline fuel costs and 10,000 tons of greenhouse gas emissionsâthe equivalent of taking 1,900 cars off the road (Port of Seattle, 2014). United reports that through the end of 2018, it has converted 27% (4,318 pieces) of its GSE fleet to electric at approximately 120 airports (A. Robinson, personal communication, Feb. 4, 2019). â¢ Solar photovoltaic: As of 2016, more than 70 U.S. airports have developed solar photo- voltaic (PV) projects to generate emissions-free electricity. By replacing fossil-fuel fired electricity, solar PV has offset a total of 74 million metric tons of CO2 in the United States (Solar Energies Industry Association, n.d.). Airports are increasingly turning to solar to meet their electricity needs, with an annual increase in airport-based solar projects of 7.5% between 2012 and 2016 (Barrett, DeVita, Kenfield, Jacobsen, and Bannard, 2016). â¢ Heating demand reductions: As identified in ACRP Report 56, one of the most effective approaches to reducing GHG emissions at airports is reducing energy demands for heat- ing. Some of the most innovative programs currently harnessing this technology have been installed at small and medium-sized airports. These projects demonstrate the measurable progress of solar thermal and other renewable thermal technologies, as evidenced by a decrease of 85% in heating-related GHGs at Boise International Airport (BOI). 1.3.2 Funding Initiatives and Incentives â¢ The FAAâs Voluntary Airport Low Emissions (VALE) Program is the primary program advancing airport air quality improvements. Created in 2004, the program supports emis- sion reduction projects at airports located in the United Statesâ most polluted areas. Air- ports located in these EPA-designated nonattainment zones are eligible to apply for VALE grants to implement emission reduction projects. Funding can be used for gate electrification,
Introduction 13 electric ground support equipment, alternatively fueled vehicles, renewable thermal projects that directly offset emissions from building heating systems, and other airport air quality improvements. The funding is discretionary, meaning it does not limit the airportsâ funding for typical airport improvements (also referred to as entitlement funds). Annual VALE fund- ing is presented in Figure 1-3. â¢ The Zero Emission Vehicle (ZEV) Program, created through the FAA Modernization and Reform Act of 2012, allocates competitive grant funding to airports to purchase new vehicles that do not produce emissions. Eligibility is limited to electric vehicles, although other tech- nology, such as hydrogen fuel cells, could be eligible in the future. Annual allocation of ZEV grants is detailed in Figure 1-3. â¢ Energy efficiency grants: The 2012 Modernization and Reform Act gave airports the author- ity to use Airport Improvement Program (AIP) entitlement funds for energy efficiency proj- ects. Funding can be used for energy audits, energy efficiency projects, and renewable energy. Since 2012, the FAA has also approved LED runway lights for AIP funding and issued an Engineering Brief on solar LED runway lights. After completing a pilot program for funding airport sustainability master plans, the FAA also approved AIP funds for airports to prepare sustainability plans as part of their long-term planning. Many sustainability plans include GHG inventories that can lead to GHG reduction measures. â¢ Rebates and tax incentives: Economic incentives continue to include federal and state rebates and tax incentives for certain energy efficiency measures. At the same time, economic incen- tives are expanding to become key strategies for airports to decrease Scope 3 emissions (indirect emissions from nonairport sources related to activities at the airport). Airports are rewarding tenants and service companies for meeting mutually agreed-on GHG reduction standards; for example, ridesharing and transportation network companies pay lower fees when they achieve increased fuel efficiency. These creative programs produce mutually beneficial incen- tives that can be incorporated into an overall GHG emission reduction matrix (San Diego International Airport, 2018). â¢ Carbon offsets are actions or activities (such as the planting of trees or carbon sequestra- tion) that compensate for the emission of carbon dioxide or other greenhouse gases into the atmosphere. Offsets can be purchased through various programs. In aviation, offsetting for air travel is almost exclusively the only option for compensating emissions because air- craft currently only operate on fossil fuels. The International Civil Aviation Organization Note: VALE = voluntary airport low emissions; ZEV = zero emission vehicle. $0 $5,000,000 $10,000,000 $15,000,000 $20,000,000 $25,000,000 $30,000,000 $35,000,000 2013 2014 2015 2016 2017 2018 VALE ZEV Figure 1-3. FAA airport emission reduction funding.
14 Airport Greenhouse Gas Reduction Efforts (ICAO) has created the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), a policy mechanism establishing goals for emissions reduction and an offsetting program to achieve those reductions for ICAO member states and the associated inter- national aviation activities. Passengers can also purchase offsets from programs developed by airlines and other businesses and organizations. Airline offset programs are available from United, Delta, Alaska, and JetBlue (A. Robinson, personal communication, Feb. 4, 2019). The Good Traveler Program, created by SAN and administered by the Rocky Mountain Insti- tute (RMI), is an airport-led program that makes offsets available to customers. 1.3.3 Tools and Programs Several powerful tools have been developed to help airports assess their GHGs and implement effective projects. â¢ The airport carbon and emissions reporting tool (ACERT) was developed in 2013 to pro- vide airports with a simple spreadsheet tool to calculate airport GHG emissions. It specifies emissions by scope type as defined by the GHG protocol and is compatible with reporting procedures contained in the Airport Carbon Accreditation Program. As it was developed by ACI, it is currently available to ACI members. â¢ The solar glare hazard analysis tool (SGHAT) was developed by the Sandia National Labora- tories in 2013 to help airport sponsors evaluate the potential glare effects of solar PV projects on airport sensitive receptors, ensuring that solar projects are safe and compatible with avia- tion activities. As a result of the development of SGHAT and the formulation of the FAAâs Solar Policy, many airport solar projects are more confident about the review process and the compatibility of specific sites and designs with aviation activities. â¢ The airport carbon accreditation framework was first adopted by U.S. airports in 2014, when SEA became the first airport in North America to receive accreditation. Currently, 26 U.S. air- ports have received accreditation from mapping to reduction and optimization to neutrality (Airport Carbon Accreditation, n.d.). â¢ The Good Traveler Program provides evidence of industry progress since its founding by SAN to provide passengers with a direct opportunity to offset their air travel GHG emissions and fund a local emission reduction project. Ten additional airports have since joined the program as partners (Rocky Mountain Institute, 2018). â¢ The Sustainable Aviation Guidance Alliance (SAGA) allows for the pooling of information via online databases and the reporting of industry progress by documenting applied prac- tices in real time. Established more than a decade ago, SAGA catalogs airport-specific sus- tainability initiatives to create consistent, comprehensive, and consensus-based resources that advance industry efforts to reduce GHG emissions (Sustainable Aviation Guidance Alliance, 2018). â¢ Many U.S. airports are working with their government colleagues at the state, county, or municipal levels through existing climate action programs including the Climate Mayors, Americaâs Pledge, and We Are Still In. As evidenced by the case examples included in this report, many projects are implemented as part of a state or cityâs Climate Action Plan, or as a direct result of locally driven air quality or environmental policies. Of the 17 case exam- ples featured in this report, 11 include mayors who are signatories to the Climate Protection Initiative, demonstrating the distinct and compelling role that local governance often plays in GHG emissions reductions at airports (We Are Still In, n.d.). Further resources including creative financing, airport grant recipients, and technical and regulatory information are summarized in Appendix A.