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Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports (2021)

Chapter: Chapter 4 - Emissions Reduction Strategies

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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
×
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
×
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Suggested Citation:"Chapter 4 - Emissions Reduction Strategies." National Academies of Sciences, Engineering, and Medicine. 2021. Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports. Washington, DC: The National Academies Press. doi: 10.17226/25677.
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34 Emissions Reduction Strategies A core element of an emissions roadmap is a description of strategies the airport plans to use to reach its ultimate emission goals. Chapter 4 provides guidance on how to identify and select these strategies. The chapter is organized in four parts, which are summarized in Figure 12. Note that Sections 4.1 through 4.3 describe methods for reducing emissions and are in order corresponding with how most airports approach emissions planning. Section 4.4 describes how best to select the strategies identified in Sections 4.1 through 4.3. The quick start actions in the box are ideas for initiating the search for strategies. C H A P T E R 4 Quick Start Actions to Help Select Emission Reduction Strategies Use these actions to help select emission reduction strategies. • Focus on the largest emission sources. Begin the search for viable strategies by identifying the largest emissions sources in the GHG inventory (discussed in Chapter 3). At many airports, Scope 2 electricity emissions are the largest, which justifies spending more time and resources on identifying ways to reduce Scope 2 emissions than on other sources. Spend less time identifying strategies to address small emission sources. • Stay organized. For each emission reduction strategy under consideration, keep notes on the potential cost, emission reduction potential, timeline, and personnel needed to ensure success. These items will come in handy when selecting a final set of strategies. Section 4.1: Reduce Scope 1 and Scope 2 Emissions Section 4.2: Offset Emissions Section 4.3: Reduce Scope 3 Emissions Section 4.4: Select Strategies Figure 12. Steps to identify emission reduction strategies.

Emissions Reduction Strategies 35   4.1 Reduce Scope 1 and Scope 2 Emissions This chapter provides guidance on identifying options for emissions reductions for Scope 1 and Scope 2. Because there are far too many potential strategies to include in this guidebook, the following text provides a high-level discussion of six strategies: energy efficiency, heating and cooling technologies, renewable electricity consumption, airport-owned and airport-operated vehicles, waste management, and other (Table 10). For additional information on strategies, Table 11 highlights important resources and reports that provide practical guidance on emission reductions at airports. Two of the more comprehensive resources of strategies for airport GHG emissions reduc- tion are Appendix A of ACRP Report 56 and the sustainable practices library on the Sustainable Aviation Guidance Alliance (SAGA) website. SAGA strategies include broad sustainability efforts in addition to emissions reduction. ACRP Report 56 produced a handbook, a decision- support tool, and a set of 125 emissions reduction strategy factsheets with case examples to support airports in GHG emissions reductions. Though now several years old, many of the Strategy Category Description Energy efficiency • Energy efficiency improvements in airport-owned buildings Heating and cooling technologies • Upgrading of heating and cooling technologies in airport-owned buildings that lower airport energy consumption Renewable electricity consumption • Conversion of electricity to renewable sources, either through on-site renewables or off- site electricity purchases Airport-owned and airport- operated vehicles • Procurement of zero-emission vehicles for airport -owned fleet vehicles • Use of low GHG fuels (e.g., biodiesel, renewable diesel) in airport-owned fleet vehicles • Reduction in discretionary trips Waste management • Implementation of a composting program for food waste, etc. • Implementation of a recycling program Other • Carbon sequestration (e.g., forest carbon management) Table 10. Strategies to address Scope 1 and Scope 2 emissions. • Mitigate then offset. Airports interviewed in the writing of this guidebook stressed the importance of mitigating emissions before offsetting. Interviewees noted that offsets lessen the interest of staff in finding innovative and forward-leaning mitigation strategies. • Review recent audit reports. Airports routinely do energy efficiency or weatherization audits. These audits can provide valuable starting places for emission reduction strategies and often include the costs of the strategy. • Start with the most cost-effective strategies. Early successes that reduce emissions and save money over a short period (e.g., energy-efficient light bulbs) should be the first initiatives undertaken. Starting with the obvious and easily implemented changes builds confidence in senior management and paves the way for more costly or complex strategies later. • Do not let the perfect be the enemy of the good. Finally, think of the roadmap as a living document that can be updated over time. Develop an initial set of strategies with the intent to review and revise those strategies every few years.

36 Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports compiled strategies are still relevant, and each factsheet contains helpful information about financial considerations, implementation considerations, and potential emissions impacts. The research team also reviewed the availability of emissions calculators and several tools, including emissions inventory tools, project-specific emissions evaluation tools, and cost- benefits of emissions reduction strategies that exist to assist airports in emissions planning, as described in Table 12. Resources for other types of institutions may also be useful, particularly for overlapping sectors like buildings or ground transportation. The Carbon Neutral Cities Alliance’s Frame- work for Long-Term Deep Carbon Reduction Planning (2015) and Rocky Mountain Institute’s Carbon-Free City Handbook (2017a) offer outlines and links to in-depth resources for strategies from leading-edge cities striving for zero emissions. Some strategies in these resources are about cities reducing their own emissions, and others are more policy focused to incentivize or mandate change among the broader public. These strategies may also be relevant as air- ports consider ways to cut Scope 3 emissions by guiding tenants and other third-party actors or exploring partnerships with the cities their airports serve. Energy Efficiency Airports in search of emissions reduction strategies with low costs and short payback periods should first consider energy efficiency improvements to their existing facilities. In particular, Resource St ati on ar y so ur ce s Su rf ac e ve hi cl e tr av el W as te m an ag em en t El ec tr ic ity c on su m pti on Ai rc ra ft e m is si on s O th er O ffs et s ACRP Synthesis 21: Airport Energy Efficiency and Cost Reduction (2010).  ACRP Synthesis 42: Integrating Environmental Sustainability into Airport Contracts (2013).        ACRP Report 56: Handbook for Considering Practical Greenhouse Gas Emission Reduction Strategies for Airports (2011).        ACRP Report 78: Airport Ground Support Equipment (GSE): Emission Reduction Strategies, Inventory, and Tutorial (2012).  ACRP Report 158: Deriving Benefits from Alternative Aircraft-Taxi Systems (2016).  Carbon Neutral Cities Alliance. (2015). Framework for Long-Term Deep Carbon Reduction Planning.     Chicago Department of Aviation. (2012). Sustainable Airport Manual.      Federal Aviation Administration. (2018). Technical Guidance for Evaluating Selected Solar Technologies on Airports.   Federal Aviation Administration. (2012). Aviation Greenhouse Gas Emissions Reduction Plan.  IATA. (2013). Technology Roadmap.  Hall, Pavlenko, and Lutsey (2018). Beyond road vehicles: Survey of zero-emission technology options across the transport sector.  Rocky Mountain Institute (2017b). Innovative Funding for Sustainable Aviation Fuel at U.S. Airports.  Rocky Mountain Institute. (2017a ). The Carbon-Free City Handbook.       Sustainable Aviation Guidance Alliance. (2018). Sustainable Practices Library.        Table 11. Resources for strategies to address airport greenhouse gas emissions.

Emissions Reduction Strategies 37   airports with older facilities are likely to find ample opportunities to increase energy efficiency. Table 13 is an example of how to organize the costs of energy efficiency strategies in one table to help with selection. Each measure in the table has a different payback period—some pay back very quickly and others take 10 years or more. ACRP Synthesis 21: Airport Energy Efficiency and Cost Reduction documents low-cost energy efficiency practices implemented by airports and includes a comparison of the cost and payback period (Lau, Stromgren, and Green 2010). Airports can also refer to ACRP Report 56 for a list of energy efficiency strategies, such as developing energy performance contracting Year Name Author Description 2012 Handbook for Evaluating Emissions and Costs of APUs and Alternative Systems ESA (2012) This report includes guidance on emissions estimations at airports, as well as an Airport Emissions Estimator Tool. 2017 ACERT Model ACI (2017) ACERT is an Excel-based tool that airports can use to calculate their own GHG emissions inventory. 2017 AEDT Model FAA (2018b) This software system models aircraft performance in space and time to estimate fuel use, emissions, noise, and air quality consequences for scenarios ranging from a single flight at an airport to global levels. 2017 GREET Model Wang et al. (2017) This full life-cycle model evaluates energy and emissions impacts of alternative transportation fuels and vehicle technologies. 2017 AFLEET Tool Burnham (2017) The AFLEET tool facilitates estimating petroleum use, GHG emissions, air pollutant emissions, and cost of ownership of light-duty and heavy-duty vehicles using simple spreadsheet inputs. 2014 MOVES2014b Model EPA (2018) This emissions modeling system estimates emissions for mobile sources at the national, county, and project levels for criteria air pollutants, GHGs, and air toxins. 2017 EMission FACtor (EMFAC)Model CARB (2021) This model is used to assess emissions from on-road vehicles including cars, trucks, and buses in California, and to support CARB’s regulatory and air quality planning efforts. 2018 Electric Vehicle EmissionsCalculator UCS (2018) This calculator compares emissions of plug -in hybrid electric and battery electric vehicles to gasoline-only vehicles, by ZIP code and the make, model, and year of a vehicle. 2016 Petroleum Reduction Planning Tool DOE (2018) This tool assists fleet managers in helping them to plan to reduce fossil fuel use and resulting GHG emissions. Table 12. Sustainability tools to help reduce emissions at airports. Energy Saving Measure Initial Cost Annual Savings Source of Annual Savings Years to Payback Net Present Value (20 Years) Assumptions Efficient lighting $50,000 $25,000 10 megawatt electricity savings, labor savings of $1,000 2 years $305,310 Cost of electricity and liquid fuels increases at 3% per year. Interest rate of 3%. Rebates for measures included. Building wall and ceiling insulation $50,000 $5,000 600 gallons #2 fuel oil reduction, 3,000 cubic feet natural gas, 26 megawatt electricity 10 years $21,062 Window and door sealing $40,000 $4,000 500 gallons of #2 fuel oil, 2,000 cubic feet natural gas, 24 megawatt electricity 10 years $16,849 Table 13. Lifecycle cost analysis for potential energy efficiency strategies.

38 Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports partnerships, improving insulation of the airport building enve- lope, installing LED lighting for runways and taxiways, installing automated building control systems or variable frequency drives, and developing and marketing an energy conservation program for building users. Appendix A of ACRP Report 56 details information about each strategy, including financial considerations, implemen- tation considerations, potential impacts, potential limitations, and case study examples. The Sustainable Airport Manual developed by the Chicago Department of Aviation includes energy efficiency measures as part of its rating system, accompanied by case studies for certain measures. The case study that focuses on energy efficiency efforts at Los Angeles World Airports (LAWA) details that LAWA has upgraded 80% of its building air handling units with variable speed drives and 60% of computer servers to high efficiency servers and has retrofitted buildings with energy-efficient lighting (Chicago Department of Aviation 2012). Heating and Cooling Technologies Heating, cooling, and ventilation can make up a substantial portion of Scope 1 emissions at most airports. In general, an airport should approach heating, cooling, and ventilation improvements by beginning with the end state and progressing toward the source (downstream to upstream). In other words, the first step should be to reduce heating or cooling demand through building envelope improvements. The next step should be to pursue retrofits, from the end points all the way back through the distribution system (e.g., fixing leaky ducting and add- ing zones). The final step would be to retrofit or replace the sources, such as purchasing a new furnace or converting a constant volume to a variable volume system. This sequencing is important for two reasons— the downstream improvements are typically cheaper and have a faster payback and the result of the downstream improvements informs subsequent measures upstream, such as by allowing the purchase of a smaller furnace/boiler. After investing in insulation and other building envelope effi- ciency measures, an airport should consider addressing forced air duct leakage and possibly adding heating zones. It is relatively inex- pensive to limit those losses by sealing leaks and, where feasible, insulating ducts. Zoned heating systems can save energy if parts of an airport building have different temperature requirements and can be closed off from one another. A zoned system can provide a different amount of heat to each zone, depending on its usage. A building can be zoned in several ways. Some multizone systems have only one furnace/boiler and use electrically controlled dampers, which can open or close depending on the heating needs of different zones. Other systems have separate furnaces/boilers for each zone. In the final step of source replacement, airports should consider switching to cogeneration (also known as combined heat and power or CHP), which uses an engine to generate electric- ity and recovers the waste heat for use. Trigeneration (also known as combined cooling, heat and power or CCHP) is the simultaneous production of electricity, heat, and cooling from a single energy source. Similar to CHP, the waste heat by-product that results from electric- ity generation is captured and used for heating or cooling. Cogeneration and trigeneration systems are typically more efficient than purchased electricity or fuel because they use waste Airports Improving Efficiency of Heating and Cooling Nantucket Memorial Airport installed efficient infrared heating units in their garages. SFO is in the process of getting a heat recovery chiller facility, which will help with efficiency and displace natural gas. Toronto Pearson International Airport is installing electric backup boilers for their heating system. These offer the airport a cleaner alternative to its existing natural gas boilers, adds redundancy to the system, and saves the airport money because it can switch to the electric boilers during off-peak hours when electricity is less costly. “The most sustainable energy is the energy you don’t use.” Denise Pronk, Program Manager, Corporate Responsibility, Royal Schiphol Group

Emissions Reduction Strategies 39   heat and avoid transmission losses. Canberra International Airport in Australia installed a trigeneration system to provide power for four office buildings, resulting in the reduction of more than 1,000 tons of CO2 emissions and $160,000 per year in energy costs (CDM 2011). Ground-source, or geothermal, systems can be used either to heat water or to heat or cool indoor space. These systems use the ground as a heat source during the winter and a heat sink during the summer because ground temperatures remain relatively constant. Geothermal systems can sig- nificantly reduce the amount of electricity or fuel needed to heat or cool a building, thus reducing associated GHG emissions. Nantucket Memorial Airport installed a geothermal heating and air conditioning system that allowed the airport to replace two oil-burning furnaces and thus decrease GHG emissions. ACRP Report 56 documents additional strategies to consider for clean heating and cooling, including solar desiccant air conditioning systems, on-site biomass energy systems, sewer heat recovery systems, and using natural bodies of water for cooling. Airports are encouraged to review the description and considerations included for each strategy to determine which ones may be feasible for their facilities. Renewable Electricity Consumption Installation of on-site renewable electricity generation is increas- ingly attractive, given the declining costs and added protection against short-term blackouts or long-term utility outages. The most common on-site renewable electricity systems are solar powered, although on-site biomass energy production, building-mounted wind turbines, geothermal heating and cooling systems, or geothermal snow and ice melting systems are also potential options at airports. Finally, waste-to-energy systems and gas produced from local landfills are other ways to recycle waste and produce valuable low-carbon electricity (CDM 2011). Purchase of off-site renewable electricity is another option for lowering Scope 2 emissions. Depending on its location, the airport may be able to buy a green pricing product or green marketing product from the elec- tricity provider. The airport typically pays a small premium in exchange for electricity generated from renewable power resources. The premium covers the increased costs incurred by the power provider (i.e., electric utility, when adding green power to its power generation mix).3 Another option is to develop power purchase agreements (PPAs), either for renewable energy generated on site or in some cases off site (requiring certification and issuance of renewable energy credits or RECs). In 2018, the FAA updated its in-depth guidebook for airport solar development, documenting case studies from the 15 airports that have invested in solar technologies. It also provided guidance on key issues for airports to navigate including glare and reflectivity issues that might cause vision loss to pilots arriving or departing, or to air traffic control personnel. Another issue detailed in the solar guide is that electromagnetic interference with radar systems may create false signals and communications interference (FAA 2018a). Other key sources of guidance for airports on renewable energy strategies include ACRP Report 56, ACRP Research Report 197: Guidebook for Developing a Comprehensive Renew- able Resources Strategy (Shaw et al. 2019), and ACRP Research Report 228: Airport Microgrid Implementation Toolkit (Klauber et al. 2021). 3 In competitive markets, airports can choose to purchase green marketing products from providers other than their local utility. In regulated markets, airports may be able to buy a green pricing product from their local utility. Electricity Grid Mix Considerations When evaluating renewable electricity projects, it is vital to consider the electricity grid mix. If the grid mix includes large amounts of electricity generated by burning coal, then projects improving efficiency or switching to renewable electricity will have an outsized impact compared to if the grid mix were heavily produced through emission-free hydropower. For example, in Montreal where electricity is heavily generated via hydropower and thus nearly emission-free, switching heating and cooling to electricity makes more sense than in areas with a coal- intensive grid.

40 Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports Airport-Owned and Airport-Operated Vehicles Airport-owned or operated cars, trucks, and buses are a major Scope 1 emission source for most airports. These vehicles (and their emissions) fall under the control of the airport and are different from Scope 3-related vehicles such as airline-owned ground support equipment, externally owned ground transportation vehicles (e.g., taxis, limousines, city transit buses), and personal vehicles. At many airports, airport-owned and operated vehicles can number in the hundreds or even thousands and include work trucks, office pool vehicles, emergency service vehicles, security vehicles, and shuttle buses (e.g., between terminals). Options to lower emissions from these vehicles include swapping fuels to a less-carbon intensive fuel (e.g., fleet electrification), reduc- ing the amount of vehicle travel, or shifting to more efficient vehicles (i.e., towards vehicles with lower fuel economy). As described in ACRP Synthesis 85: Alternative Fuels in Airport Fleets (Morrison, Fordham, and Fields 2017), fleet electrification is emerging as the preferred strat- egy in recent years due to the financial savings and elimination of all tailpipe emissions. However, other fuel-swapping strategies are common, including use of renewable natural gas, conventional natural gas, biodiesel, and renewable diesel. During development of the airport emissions roadmap, airport staff should work closely with the fleet manager to answer the following questions: 1. What is the current vehicle composition (i.e., how many sedans, pickup trucks, buses, etc.)? 2. Does the airport-owned or operated fleet have an existing fleet sustainability goal (e.g., 25% of vehicles are electric by 2025)? 3. How many new vehicles are procured and retired each year (thus, informing the potential rate of conversion)? 4. Are there any restrictions that prevent the use of certain fuels (e.g., contractual items, safety codes)? Answers to these questions help inform the potential timing and impact of emission reduc- tions from fleet vehicles. For purposes of the emissions roadmap, a rough estimate on emissions reduction potential may be sufficient. However, prior to actually converting vehicles to a different fuel or power train, fleet managers should conduct a detailed suitability study that examines costs, vehicle options, routes, fueling locations, and operational feasibility. This type of study helps fleet operators prioritize vehicles for replacement, develop a fleet conversion schedule, and understand infrastructure requirements. Waste Management As waste materials decay in landfills or get burned in incinerators, they release GHGs. Airports can adopt waste management tactics to reduce emissions from the waste stream, including recycling, composting, waste reduction efforts, and improvements to wastewater treatment facilities, where applicable. Strategies may include a solid waste management plan, a waste reduction and recycling program, separating and composting food waste, and others that can help reduce methane (CH4) and other GHGs from the waste stream (CDM 2011). As a first step, airports should focus on source reduction and reuse, since generating fewer waste materials reduces emissions associated with waste collection, transportation, and dis- posal. Source reduction and reuse avoid emissions regardless of whether materials would have Airport Fleet Vehicles Airport fleet vehicles occupy a unique niche among all vehicle fleets, with hundreds or even thousands of diverse vehicles. Emissions inventories suggest fleet vehicles are one of the primary sources of emissions at airports. For example, at the Philadelphia (PHL), Los Angeles (LAX), and Minneapolis- St. Paul (MSP) International Airports, fleet vehicles account for 38%, 43%, and 45% of Scope 1 emissions, respectively. Besides helping reduce emissions, alternative fuels can help airports manage fuel costs, reduce petroleum dependence, increase energy security, improve public image, and potentially reduce maintenance efforts.

Emissions Reduction Strategies 41   been processed for disposal or recycling. In addition to materials management, airports with wastewater treatment facilities have opportunities to reduce emissions by converting output gases to usable energy. Airport wastewater treatment systems that have anaerobic digesters to treat de-icing fluids may use the methane generated from the digesters to produce heat or electricity instead of venting the methane to the atmosphere. The Albany Airport in New York has implemented such a system (CDM 2011). Airports can apply this waste-to-energy concept to solid waste materials too. Gatwick Airport constructed an on-site materials recycling facility which increases the airport’s reuse and recycling rate and converts waste to low-carbon energy (Gatwick 2016). In the future, airports may be able to supply their solid waste as jet fuel feed- stock, partnering with companies that apply a Fischer-Tropsch technology to convert this feedstock to jet fuel. Additional information regarding waste management best practices is avail- able in ACRP Synthesis 92: Airport Waste Management and Recycling Practices (Turner 2018), ACRP Report 100 (Cascadia Consulting Group 2014), Recycling, Reuse, and Waste Reduction at Airports—A Synthesis Document (FAA 2013) and Guidance on Airport Recycling, Reuse, and Waste Reduction (FAA 2014). Other Other emissions sources at airports might include construction activities, firefighting training exercises, refrigerant leaks, and others. Even relatively small emission quantities of GHGs like methane and refrigerants have significant outsized climate impacts due to their higher global warming potentials—about 2,000 times higher in the case of common refrigerants—compared to CO2 (CARB 2019b). Construction activities result in GHG emissions through many of the same mechanisms as discussed above: fossil fuel combustion by construction vehicles, process- ing and disposal of construction waste, and lighting and other energy uses. Airports can reduce construction emissions through policies that require the use of low- emission construction vehicles and equipment, recycling and reuse of construction materials, and use of energy efficient lighting during the construction process, for example (CDM 2011). As part of its Chicago O’Hare Modernization Program (OMP), the Chicago Department of Aviation (CDA) implemented tailpipe emissions standards for construction equipment that were later adopted as city-wide policy. CDA incorporated the standards into construction bid documents and established an enforcement mechanism by requiring emissions documentation to be attached to invoices prior to approval. Even though CDA was not mandated to, it required the use of ultra-low sulfur diesel (ULSD) for certain vehicles when the OMP began because air quality was a priority for such a large project. These policies not only reduced GHG emissions and criteria pollutants but also may have bolstered the market for ULSD (Chicago Department of Aviation 2012). Firefighting exercises at airports typically involve firefighters training in a live-fire envi- ronment. These training exercises result in GHG emissions from fire suppression chemicals. Airports are encouraged to work with training staff to optimally plan exercises such that the minimum amount of fuel is used while still providing necessary training. The EPA, in part- nership with four major associations representing the fire protection industry, developed a voluntary code of practice to minimize emissions of two GHGs used as fire protection agents: hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs). The emissions reduction strategies in the code of practice include adopting maintenance practices that reduce leakage as much as technically feasible, limiting discharge for system testing to what is essential for performance requirements or required by regulation, and ensuring that technicians who handle equipment containing HFCs and PFCs are trained to minimize emissions. Hydrochlorofluorocarbons (HCFCs) and HFCs and are two GHGs used in refrigeration and air conditioning systems. HFCs and HCFCs are emitted during operation, repair, and disposal, unless recovered, recycled, and ultimately destroyed (EPA 2016c). Airports can take several

42 Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports steps to minimize the release of these GHGs, including utilizing natural refrigerants where possible, installing intelligent fault diagnosis systems to detect leaks, using vapor compression heat pumps, and installing microchannel components and heat exchangers to reduce the number of refrigerants used. Guidance for each of these strategies can be found in ACRP Report 56. 4.2 Offset Emissions A carbon offset program “reduces, avoids, or sequesters GHGs in order to compensate for emissions occurring elsewhere” (Ritte 2011). These programs can be made up of myriad project types, from supporting forestry expansion to renewable energy. Often there are markets where enti- ties can trade accredited offsets, essentially allowing them to purchase the right to say they reduced emissions without actually having undertaken the emissions reduction project. Being accredited is the official acknowledgement that 1 ton of CO2 emissions were displaced. Some regulating bodies use offsets as a way to regulate carbon emissions (as opposed to a flat tax on carbon, or other approaches). One such example of this is CORSIA (discussed in Section 1.2), which has established voluntary goals for 2021–2026 and mandatory offset minimums for 2027–2035 (ICCT 2017). Airports can adopt carbon offset projects voluntarily or in response to compliance measures. Compliance-based carbon reduction programs, such as the Regional Greenhouse Gas Initia- tive (RGGI) in North America, are regulated by mandatory international, national, or regional entities to require participants to reduce or offset CO2 emissions ACRP Report 57: The Carbon Market: A Primer for Airports (Ritter, Bertelsen, and Hazeman 2011). Demand for compliance- based carbon offsets is created by a regulatory instrument (CORE 2019). Carbon offset market participation and demand can be also driven voluntarily by national, regional, organizational, or individual interest in CO2 emissions reductions, though there are no rules or regulations established for voluntary offset trading (CORE 2019). ACA is one of several organizations that acknowledge airports that reduce their emissions of carbon. In December 2018, the organization published Issue 1 of the Offsetting Guidance Document to provide airport users with a concise overview of the global carbon offsetting management accreditation program, guidance on offsetting options, key offsetting quality criteria and recommendations, and practical and applicable support (ACA 2018b). The docu- ment includes term definitions, examples of carbon offset project types, and GHG mitigation actions ranked by level of confidence, procurement guidelines, a list of independently verified offset programs, and more. Although there is a cost to becoming ACA-certified, airports can use the resources and framework without obtaining the official certification. This can be a great way to get started and realize some of the benefits of zero- or low-emissions planning for any airports that are financially or otherwise resource constrained. According to the ACA offsetting guidance, several criteria may be used to evaluate the quality of a carbon offset program (ACA 2018b). The criteria can be separated into mandatory and optional categories. Mandatory criteria include additionality (i.e., the emissions reduc- tions would not have occurred in the absence of the offset) and permanence (i.e., the offset is not reversible). Most offset programs are geared toward airline emissions rather than airport emissions. Airports interviewed for this guidebook typically purchase offsets from local organi- zations so airport funds stay within the jurisdiction. Other major offset programs are described below, some of which are only for offsetting airline travel. Certified Emissions Reduction A certified emissions reduction (CER) is a certificate issued by the United Nations to member nations for preventing 1 ton of CO2 emissions. United Nations Clean Development Mechanism

Emissions Reduction Strategies 43   (CDM) allows Annex I Parties, countries with developed or tradi- tional economies, to purchase or trade CERs to help them achieve emissions reduction targets under the Kyoto Protocol while support- ing sustainable development in developing countries. For projects to be CDM-accredited and eligible for CERs, they must create real, measurable, and long-term benefits to climate change mitigation and produce additional emissions reductions that would not have other- wise occurred. Companies can also purchase CERs to contribute toward their own emissions reduction targets under mandatory emissions trading schemes, such as the European Union Emissions Trading Scheme, or voluntary schemes. Proprietary Verified Emissions Reduction Unlike CERs and EUAs, verified emissions reductions (VERs) are exchanged in the voluntary market, which function outside and in parallel of the regulatory market. VERs can be created under CDM or under other standards (e.g., Gold Standard, Voluntary Carbon Standard, VER+) operating in the voluntary market. CERs can be accepted in both the regulatory and voluntary market, but VERs are accepted only in the voluntary market. Although the voluntary market is smaller and does not have established rules and regulations, its lower development and transaction costs enable entities to experiment with new methodologies and technologies under small projects. The Good Traveler The Good Traveler is a nonprofit, established by and for airports, which allows passengers to mitigate the environmental impact of their flight through the purchase of a carbon offset. Through the purchase of a $2.00 Certified Carbon Offset, a passenger offsets the carbon released in 1,000 miles of flying (or 400 miles of driving). Funds generated through The Good Traveler support projects that offset carbon, including renewable energy, landfill carbon capture and reuse, and waste composting, among others. 4.3 Reduce Scope 3 Emissions Scope 3 emissions are those under the control of tenants, passengers, employees, or other organizations at the airports and are typically the largest (by far) category of emissions at an airport. Addressing Scope 3 emissions can be challenging for a number of reasons. First, it can be unclear which entity is responsible for the emissions. Additionally, emission reduction programs require coordination and cooperation with third parties and/or tenants, which becomes more arduous as the number of partners increase. Partners may not be aligned toward the same social goals as the airport and may see any effort to reduce Scope 3 as an infringement. Despite the various challenges, airports are increasingly finding creative and novel approaches for addressing Scope 3 emissions. In many cases where an airport cannot directly mandate emis- sion reductions, it can encourage the reductions through positive reinforcement and awards. Simply being prepared and available to assist when tenants want to pursue an emissions reduc- tion strategy can be an option, which is how SFO is approaching SAF. Similarly, some airports have sought to educate tenants by paying for consultants or energy analysts to come and offer free evaluations to show the tenants how they could save money from efficiency measures that reduce emissions. Another possible strategy is to reduce administrative and logistical barriers Offsets and Revenue Diversion FAA considers use of airport revenue for costs associated with airport carbon accreditation programs, including the voluntary purchase of carbon offsets, within the boundaries of permitted operational costs as discussed in the Revenue Use Policy (64 Fed. Reg. 7696, February 16, 1999). When these costs are directly and substantially related to the airport, (i.e., the carbon offsets purchased are based on the carbon generated by the airport) the benefit of the offset accrues directly to the airport sponsor.

44 Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports to support emissions reduction (such as installing electric vehicle chargers). A specific example of a Scope 3 emission reduction program at Hong Kong International Airport is shown in the box and Figure 13. Airport Policy Measures Airports can implement policies to encourage airlines and other tenants to adopt cleaner technologies and practices. For example, airport contracts for design and construction, conces- sions and tenant lease agreements, and janitorial service contracts are an opportunity to drive airport environmental practices. ACRP Synthesis 42: Integrating Environmental Sustainability into Airport Contracts provides an overview of contract-based emissions reduction options (Haseman 2013). Green leases, as defined in Green Lease Guide: A Guide for Landlords and Tenants to Collaborate on Energy Efficiency and Sustainable Practices by Building Owners and Managers Association International, allow tenants and airports to come to an agreement that shares the cost of any improvements, allowing both parties to benefit by seeing reduced operating costs (Jossi 2018). Green leases with tenants are described in Section 5.3. Airport Authority Hong Kong Data Tracking and Sharing Platform In seeking to reduce emissions not directly under its control, the Hong Kong International Airport faces the challenge of having 73,000 workers who are not under the direct authority of the airport. Furthermore, the airport has a large amount of non-aeronautical activity on the airport—40% of emissions are from airport operations and 60% are large on-airport business partners. To help address these challenges, in 2011, Airport Authority Hong Kong (AAHK) built a carbon audit system that enables it to track, understand, set a reduction target, and report on “airport-wide” emissions of 53 airport business partners (ABPs) (Figure 13). Each company has its own password-protected space on the platform, and AAHK discloses only the collective performance of the whole airport community. AAHK provides the software for free and offers free training. Participating ABPs upload their data every 6 months. According to airport staff, this system builds trust with the partners and encourages reductions in Scope 3 emissions. Figure 13. Airport Authority Hong Kong data tracking and sharing platform.

Emissions Reduction Strategies 45   A memorandum of agreement (MOA) can be received more favor- ably by tenants than a green lease (see Section 5.3). MOAs are often viewed as business contracts by tenant legal departments, who are not always receptive to including emissions goals. When considering how to encourage tenants to reduce emissions, airports can enter into an MOA, allowing tenants greater flexibility on timing and amend- ments. This option may be especially attractive in a weak economic environment when tenants value extra flexibility outside of a lease agreement. Ground Support Equipment ACRP Report 78: Airport Ground Support Equipment (GSE): Emissions Reduction Strategies, Inventory, and Tutorial documents the various types of ground support equipment (GSE), functions, suppliers, and ultimately strategies to reduce emissions from these vehicles (CMD Federal Programs Corporation 2012). Emissions from GSE can cre- ate more localized air quality impacts so these have been a concern of airport stakeholders and are subject to federal and state emissions regulations. One set of strategies includes terminal gate electrification projects, such as replacing diesel-powered air conditioning units with fixed pre-conditioned air (PCA) systems or minimizing diesel-powered ground power units (GPUs) and aircraft start units (ASU) use at the gate through providing 400 Hz electrical systems. Other strategies encourage converting GSE to alternative-fuel vehicles and reducing extensive idling common for some airports. Airports could undertake strategies to encourage or mandate cleaner GSE operations by airlines or other tenants, including through use of emissions fees and tenant lease agreements, though challenges are often associated with implementing such strategies. Airports should be aware of space or infrastructure constraints that affect implementing GSE emissions reduction strategies. For example, some airports are space-constrained on the ramp and find it challenging to install enough chargers to fully electrify the GSE operation. Equipment typically must charge overnight and remain parked near the chargers. Highly congested airports such as Seattle-Tacoma may especially need to consider these constraints. Energy supply can also be an issue for older facilities, requiring the local utility to potentially upgrade substations feeding the airport. In recent years, there has been an increase in the viability of electrification of GSE, sometimes referred to as eGSE, due to the lowered emissions from electricity supplies in most areas of the United States as well as the improvement of electric vehicle technology and reduction in costs. Ground Access Vehicles Ground access vehicles (GAVs) refer to landside ground transportation at an airport and include vehicles used by and for airline passengers, airport employees, airline or airport tenants, and freight delivery—as discussed in ACRP Research Report 180: Guidebook for Quantifying Airport Ground Access Vehicle Activity for Emissions Modeling (Kenney 2017). These vehicles can include private vehicles, rental cars, taxis, transportation network companies (TNCs), door-to-door vans, hotel shuttles, public transport, service and delivery vehicles, and air cargo vehicles. Strategies to reduce emissions from GAVs include improved public transit, walking, and bicycle connections; consolidated rental car facilities; incentives for employees Airports Reducing GSE Emissions Through the “EV100” initiative, Hong Kong International Airport (AAHK) is one of many airports beginning to implement electrified GSE. In 2018, AAHK had 240 pieces of electric GSE equipment and is continuing to expand this electrified fleet. Indira Ghandi International Airport is employing TaxiBots—electric semi-robotic, pilot- controlled towing tractors—in an effort to reduce emissions from GSE while taxiing planes to the runway.

46 Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports to take public transit, walk, or bicycle to work; incentives for passen- gers, taxis, limousines, TNCs, or employees arriving in zero emission vehicles; conversion of vehicles like airport shuttles to alternative fuel vehicles; and avoiding construction of new parking capacity (Chicago Department of Aviation 2012). Airports can also encour- age private ground transportation operators to implement strategies to decrease the number of empty rides, or trips without passengers, that drivers take. ACRP Synthesis 89: Clean Vehicles, Fuels, and Prac- tices for Airport Private Ground Transportation Providers provides more detailed guidance on several of these policy options (Kolpakov, Sipiora, Huss 2018). One example of a creative program addressing GAV emissions is at Amsterdam Airport Schiphol. The airport targeted taxi electrification as a key goal and by 2018 was served with 167 Tesla Model S taxis. The airport has heard positive reviews from customers about the comfort and from the operators because of reduced maintenance costs. Addi- tionally, although the airport has little influence on community transit agencies, it managed to sway decision-makers and help obtain a zero-emission requirement for the community buses. As of 2018, these adjacent communities operate 100 electric buses. The airport believes that having adopted its own electric buses early on helped prove the viability of electric buses to adjacent communities. Aircraft Emissions Strategies The single largest source of emissions at airports is aircraft. Aircraft design and airline opera- tional improvements have dramatically reduced fuel burn since the introduction of jet engines over 50 years ago. On a per-passenger basis, emissions are more than 80% lower than in the 1960s. However, total GHG emissions from aircraft are growing due to demand. The following discusses three broad categories of mitigation options for aircraft emissions: Taxiing, Landing, Takeoff; Sustainable Aviation Fuel; and Aircraft Technology. Taxiing, Landing, Takeoff Though airports do not have direct control of aircraft usage, they can influence industry emissions in several ways. FAA estimates that approximately 5% of aircraft emissions occur while aircrafts are on the ground or operating below 3,000 feet (FAA 2015). Strategies to reduce aircraft emissions during these phases include reducing takeoff and climb thrust, increasing efficiency during airport taxiing such as through reducing engine use, improving operational efficiency through programs like the FAA’s Next Generation Air Transportation System (NextGen), and replacing main engines for taxiing with systems such as alternative aircraft-taxiing sys- tems or equipment similar to aircraft pushback tractors. Single-engine taxi is the most prevalent approach to reducing taxiing emissions. A review of alternative taxiing systems highlighted the potential for several technology and efficiency strategies to reduce GHGs and criteria pollutants, particularly electrified technologies, yet also noted that the operational and fiscal challenges airlines and airports may face in implementing such strategies (Fordam et al. 2016). The technologies studied include dispatch taxiing (e.g., using existing aircraft pushback tractor technology), semi-robotic dispatch taxiing (i.e., similar to a San Diego International Airport’s Shuttle, Taxi, and TNC Emissions Reduction Program San Diego International Airport began with requiring emissions reductions from taxi and shuttle fleets accessing the airport in 2012. The fleets report on a monthly basis (with the make and model of vehicle, and other information) and emissions intensities are calculated. In subsequent years, TNCs have become part of the program too. In 2018, all TNCs were meeting the goal. General Aviation Leadership on Scope 3 Los Angeles Van Nuys Airport, a general aviation facility, has numerous projects to lower Scope 3 emissions. For example, the airport has six tenant solar projects underway. Additionally, in 2019, the airport became the first general aviation airport to supply sustainable alternative jet fuel to aircraft operators (LAWA 2019).

Emissions Reduction Strategies 47   pushback tractor but using a hybrid external large tractor developed specifically for taxiing), nose-wheel-mounted alternative aircraft-taxiing systems, and main landing gear alternative aircraft-taxiing systems. In the long run, airports can also incorporate more efficient design into airfield and runway layout to reduce congestion and delays (CDM 2011). Sustainable Aviation Fuel The aviation industry has jointly made a commitment to reduce GHGs through efficiency measures and voluntarily submitted to a carbon market to allow for carbon neutral growth starting in 2020 through CORSIA. The aviation industry is targeting a 50% reduction in GHGs by 2050 relative to 2005 levels. Use of sustainable aviation fuel (SAF) is an attractive strategy for reducing these emissions. Drop-in SAF can be used safely in commercial aircraft without modification and produced sustainably with renewable feedstock, including used cooking oil, tallow, energy crops, agricul- tural and forestry residues, and municipal waste (Rocky Mountain Institute 2017). For many SAFs, the fuel is burned with substantial reductions in criteria pollutants such as PM and SOx as well as modest reductions in unburned hydrocarbons. In recent years there have been several advances toward commercially viable SAF, including the inauguration of the first commercial- scale SAF refinery in the United States, the enabling of credits for SAF under government incen- tive programs at the federal (RFS2) and state (LCFS) levels, and the approval of five different fuel production pathways through the ASTM D7566 specification of synthetic turbine fuels. Though interest is growing among airports and airlines to move beyond just demonstration projects to incorporation into daily operations, several related barriers have kept SAF from penetrating the market. These barriers include low production volume, high prices compared to conventional jet fuel, and infrastructure costs for transporting and blending. One production pathway depends on fats, oils, and greases (i.e., lipids), but a potential challenge is their limited supply. This energy source is likely to become more expensive in the future as supply remains stable yet demand grows, and therefore lipid prices may increase. There is currently an insufficient supply of SAF to significantly reduce industry emissions. However, several biofuel producers are working to ramp up production. As of 2018, several production facilities were under construction. According to CAAFI, planned increase in the production of SAF is modest but meaningful and a vital step toward the viability of the fuel. This increase in production is expected to further open capital markets. The Port of Seattle has set a goal to power every flight fueled at Seattle-Tacoma International Airport (SEA) with at least a 10% blend of SAF by 2028 (Port of Seattle 2019). In 2016, the airport commissioned a study to assess the feasibility of fueling infrastructure sufficient to reach that goal, which would enable receipt, blending, storage, and delivery of an 80% jet fuel, 20% biofuel blend. The study highlighted the complex supply chain and infrastructure challenges associated with biofuels as well as the importance of partnerships to enable aircraft emissions reduction strategies. Aircraft Technology In 2013, the International Air Transport Association (IATA) released a Technology Roadmap to identify possible technological improvements to the engine and the airframe (such as aero- dynamics, lightweight materials and structures, equipment systems) to support meeting the goal set by IATA, global associations of aerospace manufacturers, airports, and other partners of reducing aviation emissions by 50% by 2050 (IATA 2013). Through modeling, researchers estimated that existing technological improvements could increase fuel efficiency by 30% for the aircraft generation after 2020, but that more advanced technologies would be necessary to meet

48 Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports the 50% by 2050 goal. The roadmap also discusses emerging but not yet commercialized tech- nologies, such as new wing designs to enable reduced weight, formation flight, battery-powered aircraft, and aircraft fuel from solar energy. Through FAA’s Continuous Lower Energy, Emissions, and Noise (CLEEN) program and NASA’s Environmentally Responsible Aviation (ERA) program, the U.S. government has been investing in research and development in collaboration with airlines to improve aviation design and, at least initially, to meet the Obama administration’s goal of achieving carbon neutral growth in U.S. aviation by 2020. CLEEN had a target to reduce fuel burn by 25% by 2015 and ERA to reduce fuel burn by 50% by 2020. Electric aircraft can offer carbon-free air travel, zero criteria pollutant emissions, reduced noise, reduced operating costs, less frequent aircraft maintenance, avoidance of safety and sup- ply chain issues associated with liquid fuels, and possible revenue generation from charging fees. Manufacturers such as Airbus have been working to develop electric aircraft models that could serve short haul flights as well as a newer concept for intra-urban air taxis. Norway is aiming to electrify all short-haul flights by 2040. Avinor, which owns and operates most of Norway’s airports, commissioned a feasibility study that concluded that battery-powered electric aircraft could serve more than 20 short routes in Norway as of the date of this publication and will be able to accommodate flights of more than 500 kilometers, or 300 miles, by 2028–2030 (Reimers 2018). 4.4 Select Strategies Unlike Sections 4.1, 4.2, and 4.3, which focus on GHG mitigation strategies, this section presents methods for visualizing, comparing, and ultimately selecting the set of strategies to be included in the roadmap. This process is an art, not a science. Each airport will have unique con- siderations when selecting its strategies. The visualization methods below are meant to help with this selection process. Although time-intensive, producing one or more of these visualizations leads to more fruitful discussions with senior management and could become central graphics in the roadmap. Figure 14 is an example of a wedge stabilization chart that shows the contribution to emissions reduction of each strategy over time. The top edge of the graphic extending up and to the right Energy Efficient Light 2020 2025 2030 2035 2040 60 0, 00 0 Building Retrofit Fleet Vehicle Electrification Solar MicrogridRemaining Emissions To ta l A irp or t E m iss io ns (T on s C O 2) Figure 14. Wedge stabilization chart.

Emissions Reduction Strategies 49   represents the path of emissions in a Reference or Business-as-Usual scenario. Each strategy contributes to a reduction from that upper line. In the figure, by 2035 the remaining emissions are zero. A wedge stabilization chart is a useful tool for visualizing the various impacts that strategies have on current GHG emissions. Figure 15 is an example of a waterfall chart which shows how multiple emissions mitiga- tion strategies reduce emissions to the level of an emissions goal. Waterfall charts show similar insights as wedge stabilization diagrams, except they do not show emissions reductions over time and are capable of greater detail in showing various emissions reduction categories (e.g., the stacked columns provide an extra layer of detail). Another method for showing or comparing various emissions reduction strategies is a mar- ginal abatement cost (MAC) curve. MAC curves are useful tools for presenting carbon emis- sions reduction costs per ton of emissions mitigated. MAC curves, such as the example in Figure 16, are comprised of discrete “blocks” that represent an individual carbon abatement measure. Blocks are organized by the marginal economic cost of emissions abatement ($/tCO2). The widths of each block reflect the amount of potential carbon emissions abatement (tCO2). The graph is ordered left to right from the lowest cost to the highest cost opportunities. Those opportunities that appear below the horizontal axis offer the potential for financial savings even after the upfront costs of capturing them have been factored in. A final method for visually comparing two or more emissions mitigation strategies is through a qualitative diagram that compares strategies across different objectives. Table 14 is an example of a comparison chart that uses Harvey balls to convey the relative score. Similarly, heat maps or simple up/down/left/right arrows help quickly turn a table with numeric values into a visually appealing diagram for the reader. Electricity Stationary Services Waste Management Surface Vehicles Other Offsets 500,000 400,000 300,000 200,000 2020 Efficient Lightbulbs Building Retrofit Fleet Electrification Solar Microgrid Offsets Residual Emissions Emission Goal To ta l A irp or t E m iss io ns (T on s C O 2) Figure 15. Waterfall chart.

50 Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports Figure 16. Marginal abatement cost curve. Excellent Good Satisfactory Poor Unacceptable Evaluation Criteria Energy Efficient Light Bulbs Building Retrofit Fleet Vehicle Electrification Solar Microgrid GHG Reduction Total $ per Ton of GHG Mitigated Total Cost of Ownership Ability to Reduce Criteria Pollutants Technology Readiness Minimal Infrastructure Requirement Administrative Burden Training Burden Table 14. Qualitative evaluation using Harvey balls.

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Airports worldwide are setting aggressive zero- or low-emissions targets. To meet these targets, airports are deploying new strategies, adopting innovative financing mechanisms, and harnessing the collective influence of voluntary emissions and reporting programs. In tandem, new and affordable zero- or low-emissions technologies are rapidly becoming available at airports.

The TRB Airport Cooperative Research Program's pre-publication draft of ACRP Research Report 220: Guidebook for Developing a Zero- or Low-Emissions Roadmap at Airports covers all steps of roadmap development, from start to finish, using conceptual diagrams, examples, best practices, and links to external tools and resources. While the main focus of this Guidebook is airport‐controlled greenhouse gas (GHG) emissions, it provides discussion about airport‐influenced emissions from airlines, concessionaires, and passengers.

Whereas other guidebooks and reference material provide airports with information on emissions mitigation and management (for example, the Federal Aviation Administration’s Airport Carbon Emissions Reduction, ACRP Report 11: Guidebook on Preparing Airport Greenhouse Gas Emissions Inventories, and the Airport Council International’s Guidance Manual: Airport Greenhouse Gas Emissions Management), this Guidebook articulates steps for creating an airport‐specific emissions roadmap.

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