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Suggested Citation:"Chapter 2 - Key Project Findings." National Academies of Sciences, Engineering, and Medicine. 2011. Handbook for Analyzing the Costs and Benefits of Alternative Aviation Turbine Engine Fuels at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14531.
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Suggested Citation:"Chapter 2 - Key Project Findings." National Academies of Sciences, Engineering, and Medicine. 2011. Handbook for Analyzing the Costs and Benefits of Alternative Aviation Turbine Engine Fuels at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14531.
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Suggested Citation:"Chapter 2 - Key Project Findings." National Academies of Sciences, Engineering, and Medicine. 2011. Handbook for Analyzing the Costs and Benefits of Alternative Aviation Turbine Engine Fuels at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14531.
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Suggested Citation:"Chapter 2 - Key Project Findings." National Academies of Sciences, Engineering, and Medicine. 2011. Handbook for Analyzing the Costs and Benefits of Alternative Aviation Turbine Engine Fuels at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14531.
×
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Suggested Citation:"Chapter 2 - Key Project Findings." National Academies of Sciences, Engineering, and Medicine. 2011. Handbook for Analyzing the Costs and Benefits of Alternative Aviation Turbine Engine Fuels at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14531.
×
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Suggested Citation:"Chapter 2 - Key Project Findings." National Academies of Sciences, Engineering, and Medicine. 2011. Handbook for Analyzing the Costs and Benefits of Alternative Aviation Turbine Engine Fuels at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14531.
×
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Suggested Citation:"Chapter 2 - Key Project Findings." National Academies of Sciences, Engineering, and Medicine. 2011. Handbook for Analyzing the Costs and Benefits of Alternative Aviation Turbine Engine Fuels at Airports. Washington, DC: The National Academies Press. doi: 10.17226/14531.
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6Over the course of the work, the project team reviewed the available information on alternative jet fuels, their effects on different engine types, airport fuel delivery processes, and the needs of the airport community. The information gained from the literature search allowed for targeted questions to be presented to the airport operators during their interviews. This chapter describes the key outcomes from the literature search and airport surveys. A thorough literature review was performed as the founda- tion of this project. The team was able to leverage the extensive work conducted by MIT researchers in support of PARTNER Projects 17 and 28. The reports from these activities provided the basis of the literature review since they provided a compre- hensive analysis of near-term feasibility of many potential fuels as well as an examination of the life-cycle GHG emissions that result from alternative aviation fuel production and combus- tion within gas turbine engines (Hileman et al., 2009; Stratton et al., 2010; and Hileman et al., forthcoming). The results pre- sented in the following pages include an identification of the fuels that are potentially viable in the next 10 years, a summary of the lessons learned by the Department of Defense regarding using jet-like fuels in diesel equipment, a summary of engine- related issues to be considered, a summary of specific consid- erations when using jet fuel in GSE, and finally a summary of the anticipated changes to emissions resulting from using alter- nate fuels in aircraft and GSE. 2.1 Potentially Viable Alternative Turbine Engine Fuels 2.1.1 Composition of Current Jet Fuel Although turbine engines can in theory operate with a broad range of fuels, the requirements of high altitude flight and the existing infrastructure place considerable limitations on which fuels could be deemed viable for use in aviation tur- bine engines. Safety is of paramount importance in terms of both handling the fuel and of aircraft operation. Fuels with high vapor pressure could lead to operability problems at cruise altitude, while those with a low flash point pose a safety hazard during fueling and operation. Some fuels decompose at temperatures typically experienced by conventional jet fuel; prolonged use of these fuels could lead to fuel system failure. Because of the low temperatures of the atmosphere where aircraft fly, an alternative jet fuel must also have a low freeze point. Fuel energy content, in terms of energy per volume and energy per mass, is another key factor that must be considered when examining alternative jet fuels. This is because an aircraft expends significant energy carrying fuel. If a lower-energy fuel is used, then additional fuel weight, as compared to Jet A, is required to deliver sufficient energy to fly a given distance. In order for the aircraft to carry this additional fuel weight, additional fuel must be carried. The increasing fuel require- ment leads to an overall increase in the amount of energy that is expended to deliver passengers and cargo between the origin and destination. Conversely, if one uses an alternative jet fuel with an increased energy per unit mass, then less energy is required to fly a given payload between two places. Therefore, in order to be viable, the fuel must have, at a minimum, an energy density comparable to conventional Jet A. 2.1.2 Source of Current Jet Fuel The American Society of Testing and Materials (ASTM) determines the requirements that jet fuel must meet for physical properties, chemical content, contaminant limits, and overall performance requirements. ASTM D1655 is the current fuel specification and enumerates all of the require- ments for Jet A. Most of the conventional Jet A purchased in the United States is produced from conventional petro- leum (i.e., crude oil). Some of it also comes from unconven- tional petroleum sources such as Canadian oil sands and Venezuelan very heavy oils. In the future, it is conceivable that C H A P T E R 2 Key Project Findings

Jet A could also be created from oil shale such as that found in Colorado. All of these sources can be refined to a hydrocar- bon fuel that meets all of the requirements for ASTM D1655. For most of this handbook, the source of Jet A will be assumed to be conventional petroleum. This will be discussed further in Section 3.4 on life-cycle GHG emissions. 2.1.3 Sulfur Content of Current Jet Fuel The specification that defines Jet A currently allows sulfur content up to 3,000 parts per million (ppm). However, the fuel sulfur content of jet fuel used throughout the United States is closer to 700 ppm (Taylor, 2009 and DESC, 2008). To reduce aviation’s impact on air quality, Jet A could be desul- furized to a level of 15 ppm; this would result in roughly a 1% increase in volumetric fuel consumption and a cost of 4 cents to 7 cents per gallon (Hileman et al., 2009, and references therein). Part of this cost is to pay for additional fuel addi- tives to ensure that the fuel meets lubricity requirements. To account for a potentially reduced fuel sulfur specification, the use of ULS Jet A is examined in this handbook. 2.2 Potentially Viable Fuels and Their Benefits Two broad types of near-term alternative fuels have been identified that could both meet ASTM D1655 (i.e., be suitable for use in aircraft) and are suitable for use in diesel-powered GSE: ULS jet fuel and SPK fuels. SPK fuels are hydrocarbon fuels with nearly zero aromatics content; this differs from Jet A or ULS Jet A, which are composed of roughly 20% aromat- ics by volume (Shafer et al., 2006). The lack of aromatics in SPK fuels affects their density and energy content; it can also lead to issues of seal compatibility, but as will be discussed shortly, there is an air quality benefit. The density of SPK fuels is below that required by ASTM D1655, but it results in a fuel that has increased energy per unit weight. If used on a typical flight, this increased energy content results in a 0.3% decrease in the energy requirement (Hileman et al., forth- coming). SPK fuels could be created from a variety of feed- stock and processes. One pathway is via F-T synthesis of coal, natural gas, biomass, or a mix of biomass and coal; another pathway is through hydroprocessing of renewable oils such as plant oils or waste greases. These fuels are termed HRJ fuels in this report. Recently, ASTM passed D7566, which approves the use of up to a 50% blend use of F-T fuels with conventional jet fuel. Efforts are ongoing to obtain similar certification of a 50% blend of HRJ fuels, with a goal of cer- tification by the end of 2010 (Rumizen, 2009). Alternative jet fuels with either reduced fuel sulfur con- tent or reduced fuel aromatics content offer the potential to reduce PM emissions. If both are reduced, as is the case for SPK fuels, then the reduction in PM emissions can be sub- stantial. This is because fuels that have lower aromatics con- tent have been shown to have reduced primary PM emissions (e.g., Corporan et al., 2007; Timko et al. 2008; Whitefield and Miake-Lye, 2008), and fuels that have lower fuel sulfur con- tent have reduced primary PM emissions and fewer emissions of SOx that would later react in the atmosphere to form PM. 2.2.1 Fuels Not Viable for Use in Gas Turbine-Powered Aircraft Blends of Jet A with either biodiesel or bio-kerosene have been discussed for aviation. Both of these fuels are created via addition of an alcohol, typically methanol, to a renewable oil source in the presence of a catalyst, such as sodium hydrox- ide or potassium hydroxide. This process is known as trans- esterification and the resulting fuel is often referred to as fatty acid methyl ester (FAME). The oil feedstock used to create bio-kerosene results in a fuel with a freeze point that is lower than that of biodiesel (roughly 0°C), but both are much higher than would be required for operations at cruise altitudes. Both of these fuels have less energy than Jet A (roughly 12% less energy by mass), and neither is suitable for transporta- tion in the existing pipeline system. Furthermore, these fuels have thermal stability issues when used in gas turbine engines. Because of these concerns, these fuels were not deemed to be viable alternatives to Jet A, and they are not considered further. Alcohols (ethanol and butanol) are not viable for use in gas turbine engines for a number of reasons, including volatility, lower energy content, lower flash point, and material com- patibility problems. Because of the many problems involving their use in aviation and the energy penalty associated with their use (see Hileman et al., 2009), alcohol fuels are not exam- ined further within the handbook. Finally, cryogenic fuels such as hydrogen and liquefied nat- ural gas (LNG) are incompatible with current infrastructure and aircraft; therefore, they are not considered in this hand- book. A summary of the fuels reviewed and their viability is presented in Table 1. 2.2.2 GSE Use of Alternative Turbine Engine Fuels In contrast to Jet A, diesel fuel, which is traditionally used to power GSE, is not required to meet D1655; instead it meets ASTM D975. One of the major factors that must be taken into consideration to ensure that a replacement for Jet A is suitable for use in a diesel GSE engine is the readi- ness of a fuel (petroleum distillates specifically) to auto-ignite. Cetane number (CN) indicates how fast the fuel self-ignites from the time the fuel is injected into the cylinder. Cetane index (CI) is estimated mathematically from CN based on 7

distillation temperatures and density. Many studies have shown that the faster the engine starts at low air tempera- ture, the lower the emissions are shortly after engine start, and the lower overall the fuel consumption is. Therefore, CI is seen as an integral environmental and operability fac- tor in diesel engines. 2.2.3 Single Battlefield Fuel (Jet Fuel Use in Diesel Engines) Most experience using jet fuel in diesel engines derives from the Single Battlefield Fuel initiative. Single Battlefield Fuel refers to the U.S. military’s strategic decision to sim- plify logistics with one fuel for all equipment when possible. Through the initiative, there is more than 20 years of experi- ence with jet fuel use in diesel engines. The Single Battlefield Fuel concept began in the late 1970s in response to differing fuel requirements by the U.S. Air Force and Army. As a result, the U.S. Air Force transitioned from JP-4 to JP-8. The rati- fication of this change occurred in 1986. JP-8, the military specification for jet fuel, is principally the same standard as Jet A, but contains additives not present in Jet A. When there is a large navy presence, JP-5 may be used as the single fuel. The transition to land vehicles operating on JP-8 was first prompted by unusually cold winters in Europe in the 1980s. The cold weather produced cold flow problems—waxing and high viscosity—in the diesel fuel. As a result, the mili- tary began mixing jet fuel, with its significantly improved cold flow properties, and diesel in a 1:1 ratio. This mix was adopted by NATO as fuel F-65, and standardizing on JP-8 became a NATO initiative. At this time, the U.S. Army already had experience with the use of jet fuel in ground equipment. Due to its cold weather properties, the army has been oper- ating on jet fuel in Alaska since the early 1970s. This includes all diesel equipment and vehicles. Large-scale testing of jet fuel in military vehicles was ini- tiated in 1988 at Fort Bliss, Texas. During the testing, over 2,800 vehicles were transitioned from diesel to JP-8. Changes in performance and maintenance were monitored for both tactical and non-tactical vehicles. In addition to monitoring equipment at Fort Bliss, the military conducted 10,000-mile performance tests using jet fuel in diesel engines. At the end of the testing period, no major problems were encountered and Ft. Bliss petitioned to continue using JP-8 as a diesel replacement. More than 19 bases have now converted to JP-8. In 1990, Operation Desert Shield used the Single Battlefield Fuel strategy with jet fuel. The U.S. military was granted per- mission by the U.S. EPA to use JP-8 for domestic on- and off-road applications in 1995. The JP-8 Single Fuel Forward, Information Compendium is periodically updated to include relevant testing and experience. Additionally, France, Norway, the United Kingdom, and the Netherlands accept standard NATO jet fuel as a diesel substitute. Due to their low sulfur and low aromatic content, F-T diesel fuels have been tested extensively for their air quality benefits. These tests tend to be dynamometer-based, short- term, and focus almost exclusively on emissions. Thus, the published literature on long-term engine effects is not as well developed (Alleman and McCormick, 2003). There have, however, been Fischer-Tropsch pilot programs in California and Sweden, as well as many years of experience in South Africa. F-T blends are currently marketed in Europe and Thailand as premium diesel blends (U.S. DOE, 2007). The majority of this F-T testing has been done using F-T diesel fuels, not the F-T jet fuel considered in this study. The main differences between these two fuels are the distillation range and the resulting cetane number. 2.2.4 Limits of Jet Fuel Use in Diesel Engines As noted in Section 2.1.3 on the sulfur content of jet fuel, the ASTM jet fuel specification (D1655) allows up to 3,000 ppm sulfur; however, jet fuel in the market has a lower sulfur content. Worldwide surveys conducted during 2007 found that annual weighted average jet fuel sulfur content ranged from 321 to 800 ppm (Taylor, 2009). As a result of the 3,000-ppm 8 Fuel Thermal Stability Freeze Point Vapor Pressure or Flash Point Energy Content Aircraft and Airport Compatible ULS jet fuel SPK FAME Ethanol Butanol Liquid hydrogen LNG Table 1. Summary of fuels evaluated.

specification, the EPA does not permit the use of jet fuel in diesel engines. EPA’s new clean diesel regulations for non- road vehicles limit sulfur content to 15 ppm. Even the new jet fuel—F-T blend specification (ASTM D7566)—would not result in sulfur that low. Only neat F-T fuel or F-T fuel blended with an ultralow sulfur jet fuel would be able to meet the EPA’s diesel sulfur limits for use in GSE. 2.2.5 Engine Modifications and Maintenance Changes The major issues identified with switching to the identified viable alternatives to Jet A are the low aromatic and low sul- fur contents. Low aromatic content is linked to decreased seal swelling, and the processing typically used to create low sul- fur content fuel can result in low fuel lubricity. Military expe- rience with JP-8 has also raised specific concerns related to low viscosity fuels and fuel pumps. In the diesel industry, a transition to 15-ppm ultralow sulfur and lower aromatics fuel has largely already occurred. California ULS diesel fuels, for example, must have less than 10% aromatics (Chevron, 2007), and aromatic contents have been observed to be as low as 1.2% (Alleman and McCormick, 2003). Issues arising from low fuel sulfur and aromatic content in the diesel industry are directly applicable to these same issues in the aviation indus- try for SPK and ULS Jet A. The first concern is that fuel leakage is possible due to reduced elastomeric swelling caused by a low aromatic content. If seals do not swell properly, fuel leakage may occur at joints in the fuel system. The standard material for these seals has been Buna-N rubber. This concern is applicable anywhere in the airport that fuel is being used. The seals in on-road diesel engines would likely not need to be replaced because manufac- turers switched materials when lower sulfur diesel standards came out in the 1990s. Leakage due to seal swell is unlikely to be an issue with the currently envisioned use of SPK fuel. Although the processed fuels themselves are low aromatic, jet fuel producers are cog- nizant of possible elastomeric complications, and an 8% minimum aromatic content is currently being used as a rule- of-thumb for minimum safe aromatic content in jet fuel. For example, a 50% F-T blend has been approved by the United Kingdom Ministry of Defense Turbine Fuel Standard (DEF STAN 91-91) because the mixture is likely to provide a mini- mum 8% aromatic content (Moses et al., 2003). Moses et al. (2003) found that elastomers tested using synthetic jet fuel with 7.2% to 16.9% aromatics had the same response as with tradi- tional Jet A-1. These concerns led to the choice of a 50% max- imum blending percentage with ASTM D7566. If, however, a fuel with significantly lower aromatic content is used, the Buna-N rubber seals will need to be identified and replaced with fluoroelastomers to prevent fuel leakage. The second concern is the low lubricity associated with the processing used to create low sulfur content. F-T fuels, for example, have shown lubricity well below accepted standards for diesel fuel (Alleman and McCormick, 2003). In the diesel industry, the low lubricity concerns have been addressed with fuel additives (British Petroleum, 2007; Chevron, 2007; Exxon, 2002). The additives contain esters (10 to 50 ppm) or fatty acids (20 to 250 ppm) (Chevron, 2007). For example, all of Exxon’s diesel fuels have incorporated lubricity additives since 2005 (Exxon Diesel FAQ, undated). Lubricity additives are esti- mated to cost approximately 0.2 cents/gallon (U.S. EPA, 2000). These fuels then meet the diesel fuel standard ASTM D975. It is important to note that the aforementioned additives may cause thermal stability problems and have not been approved for use in jet fuel; if present in jet fuel, the fuel would be con- sidered contaminated and not allowed for flight use. Also, fuels with these additives are not presently being transported within the pipeline system due to their potential for trailing back into jet fuel. Unlike for the diesel industry, however, there is no require- ment for additives to meet lubricity standards for Jet A. Lubricity additives may be added to Jet A by agreement; how- ever, most Jet A does not contain any additives (Chevron, 2006). There are, however, U.S. military standards for JP-4, JP-5, and JP-8 that require a corrosion inhibitor and lubric- ity improver, and lubricity and corrosion inhibitors may also be added to Jet A-1 (Chevron, 2000). Without a lubricity enhancer, however, the military found increased wear on fuel pumps (U.S. Army ACOM-TARDEC, 2001). In 2006, the California Energy Commission noted that based on its expe- rience, there was no reported increased engine maintenance for diesel-engine vehicles using F-T fuels (Boyd, 2006); how- ever, Alleman and McCormick (2003) note that long-term testing is still required. Therefore, unless a lubricity additive is included in ULS Jet A or SPK, there could be increased engine wear when using these fuels in diesel engines. Finally, during the military’s experience, specific issues were discovered with fuel pumps in very hot conditions. During Desert Shield/Storm, the ground vehicles were fueled with a low sulfur Jet A-1, and restarting high-mobility multipurpose wheeled vehicles after reaching operating temperature became difficult or impossible with ambient temperatures over 104°F (U.S. Army ACOM-TARDEC, 2001). This difficulty occurred in a specific Stanadyne fuel pump (model 2DB) and was traced to the low sulfur/low viscosity and dirt contamination com- bined with the lack of lubricity additive that is mandated for JP-8. Model 2DB fuel pumps are found, though not exclu- sively, in GM 6.2 and 6.5 liter engines. In response to the low viscosity fuel and restarting issues, Stanadyne issued four service bulletins (see Appendix B). Bulletin 484R specifically addresses the hot restart issues with a new hydraulic head and rotary assembly; the other service bulletins provide for fuel 9

pump changes intended to specifically adapt to low viscosity fuels, including changing certain seal components. With the exception of the Stanadyne fuel pump, however, the military has found no required modifications or adjustments to engines (U.S. Army ACOM-TARDEC, 2001), although Fernandes et al. (2007) showed that performance could be improved by specif- ically tuning engines for jet fuel. The military did not find any increased maintenance require- ments in using jet fuel in diesel engines; however, it did find several advantages. These include reduced nozzle fouling, increased fuel filter replacement intervals, extended oil change intervals, reduced potential for microbiological growth in fuel tanks, and reduced water emulsification problems in fuel tanks. With sufficient additives, the military also found reduced wear on components and reduced potential for fuel system corro- sion (U.S. Army ACOM-TARDEC, 2001). 2.3 Outcomes from Airport Surveys To understand how airports receive, test, handle, and dis- pense jet and diesel fuels, the project team visited several air- ports to interview their fuel management staff and survey their fuel storage and distribution infrastructure. (A copy of the interview form used during the visits is presented in Appendix C.) This information gave the project team a real- world context for applying the information gained from the literature. 2.3.1 Airport Fuel Management Practices Airports are complex operations, often compared to small cities. Fueling practices at airports are no different. While Jet A is by far the dominant fuel dispensed at commercial airports, many other fuels are found there as well: • Diesel fuel – GSE, maintenance vehicles, and on- and off- airport shuttles and buses; • Unleaded gasoline – GSE, fleet vehicles, and on- and off- airport shuttle vehicles; • Aviation gasoline – piston-engine aircraft; • Compressed natural gas – GSE, fleet vehicles, and on- and off-airport shuttles; and • Propane – some GSE and, most commonly, forklifts. There are many separate companies and organizations that purchase, store, and dispense fuels at airports as well, including • Fueling consortia – At many large airports, the tenant air- lines form a fueling consortium that is responsible for the lease, design, and management of the aircraft fueling sys- tem. Some consortia purchase jet fuel for all participating airlines, while others require each airline to purchase its own fuel, which is commingled in the storage tanks. Most consortia hire third-party service companies to operate the fueling system. • Airlines – At many airports, individual airlines are responsi- ble for purchasing and dispensing fuel for their aircraft and GSE. In practice, several airlines may hire the same third- party service provider to operate the fueling system. • Airports – Some airports manage the fueling system oper- ations for their tenant airlines. This is particularly true for fuels other than jet fuel, although some airports also fuel aircraft. • FBOs – Fixed based operators, or FBOs, are usually private companies located on airports that offer a variety of ser- vices such as fuel, oil, parking, hangar space, and aircraft and instrument maintenance and repair. FBOs may also offer restrooms, lounges, telephones, flight training, and baggage handling. They often manage a fuel farm to sup- port their services. • Third-party service companies – Many airport tenants, espe- cially airlines, hire private companies to provide supporting functions like operating fuel storage and distribution facil- ities, ground support functions including GSE operations, and baggage and cargo handling. Individual airports have unique combinations of these providing fuel services to aircraft and GSE around the airport. 2.3.2 Airport Fuel Infrastructure Airports all have a similar fuel infrastructure, uniquely adapted to the specific needs and organizational structure of the individual airport. The basic infrastructure described here is typical for a large hub airport with a consortium responsi- ble for aircraft fueling. Common infrastructure variations are described for the other airport types. Jet fuel is received from a fuel storage terminal managed by a major petroleum pipeline operator. The pipeline operator periodically draws volumes of different petroleum products [e.g., unleaded regular gasoline, unleaded premium gasoline, jet fuel, ultralow sulfur diesel (ULSD), off-road diesel] from the pipeline for regional storage along the pipeline route. The fuels are then redistributed to large customers, such as airports, or to secondary fuel supply companies. Marine transportation companies and petroleum refiners also operate regional fuel storage terminals, shipping and receiving fuels via pipeline, barge, oceangoing tankers, rail, and truck. Jet fuel is supplied to airports from these terminals via ded- icated pipelines or large fuel trucks. Custody transfer typically takes place at the airport fence line at a metering station or truck connection. The fuel then goes into fuel storage tanks at the airport fuel farm. 10

On-site fuel storage infrastructure includes filters and con- ditioners that ensure the jet fuel is free from water, dirt, pipe scale, rust, and similar contaminants. Tanks have gauges to track fuel storage volumes, and meters are used to track fuel quantities dispensed. Storage tanks are typically intercon- nected with pipes to provide flexibility for receiving and dis- pensing fuel simultaneously as well as supplying multiple pumps that circulate the fuel through a hydrant system or supply a truck loading rack. Fuel is dispensed to aircraft in one of two ways: through a hydrant system or via trucks. A hydrant system is an under- ground pipeline that goes from the tank farm to the terminal gate area. At the gate, a hydrant cart connects the hydrant sys- tem to an aircraft, passing the fuel through a filter and meter. Hydrant carts do not pump the fuel but use the pressure of the hydrant system to fuel the aircraft. For airports without hydrant systems, trucks deliver jet fuel from loading racks near the tank farm to the aircraft. As with the hydrant carts, the fuel trucks have filters and meters to manage the fuel loading process, although the fuel trucks do require fuel pumps. Diesel fuel is most commonly dispensed to GSE using fuel trucks. These trucks are smaller than those used for fueling air- craft since the fuel volumes transferred in each fueling opera- tion are considerably smaller. Some airports have stationary pump stands, which require the GSE to go to the stand rather than be refueled at the gate. Many airports have a mix of these systems. A third-party service provider typically manages aircraft fueling under contract to the airport’s fueling consortium or the individual airlines. The service provider owns and manages the fuel trucks and equipment, while the consortium or airport owns the tanks, pumps, and associated fixed equipment. Diesel fuel delivery is often more of a mixed bag, with multiple ser- vice providers supplying fuel for different operating entities. For example, one company may be fueling GSE for some air- lines and another company supporting other airlines, while a third company may be providing fueling services for airport- owned vehicles. Each service may maintain its own diesel storage tank(s) either on or off the airport. In addition to diesel fuel sulfur content as noted in Sec- tion 2.2.4, an important consideration for airports consid- ering using the same fuel for GSE as for aircraft is that the fuels are taxed separately. Jet fuel is often untaxed at the state level while diesel fuel is subject to state fuel taxes. Fuel taxation is very complex, reflecting international treaties and national and state legislation. Redirecting jet fuel or supplying an alter- native fuel to GSE does not change the taxation requirements since they are dependent on the vehicle serviced rather than fuel quality or other fuel property. For both aircraft and GSE, there is essentially always a fuel ticket produced at each fueling event. This ticket records fuel volumes transferred along with supporting data that may include date, time, fuel type, or temperature. The data from the fuel tickets is used for fuel use accounting, charges for fuel vol- ume, flowage fees, fuel tax reporting, and other related reports. 2.3.3 Airports Selected for Analysis Facilities at airports ranging from large, medium, and small hub airports to small non-hub airports were inspected to assess the fueling requirements, infrastructure, and fuel manage- ment practices. Airports were selected to represent a range of geographic regions and operational settings, including a large hub airport with no dominant airline, a large hub airport with a dominant airline, medium and small hub airports, a cargo- only airport, and an airport that serves primarily business jets and private aircraft. To develop information on airport fuel management practices, seven airports were interviewed and are listed in Table 2. These airports represent a sample of the range of airports that may consider the use of drop-in alternative fuels in the foreseeable future. The form used for conducting the airport inspection interviews is included in Appendix C. 2.3.4 Airport Readiness to Switch to an Alternative Fuel The airport interviews indicate that airports could readily convert to a drop-in alternative fuel for aircraft as long as the drop-in fuel is supplied to the airport. • On-airport blending has been determined to be infeasible due to cost, support needs (e.g., laboratory support and added holding tanks), and system inflexibility. • Fueling system materials at the airports studied, includ- ing connectors, pipes, tanks, filters and conditioners, hydrant systems, gauges, meters, hydrant vehicles, and 11 Large Hub Medium Hub Small Hub Non Hub Boston (BOS) Columbus (CMH) Richmond (RIC) Rickenbacker (LCK) Detroit (DTW) Ontario (ONT) Van Nuys (VNY) Table 2. Study airports.

fuel trucks, would not require modification to switch to drop-in alternative fuel. As discussed in Section 2.2.5, seal changes are not required until total aromatics fall below 8%, which will not occur within the timeframe of this study, which considers only fuel blends of up to 50% alter- native fuels. • There will be no change in the number of fueling events and, for most airports, no change in the number of fueling vehicles. This will limit the opportunity for reducing man- power even where an airport would choose to use a single fuel for aircraft and GSE. • On-airport infrastructure and operating cost savings from converting to a single airport fuel for aircraft and GSE are modest and unlikely to be a deciding factor in using an alter- native jet fuel. • In view of excise tax considerations (airlines may have to pay a higher tax rate and receive a subsequent rebate for the portion of fuel used in aircraft to ensure all fuels are properly taxed), many airports may opt for separate fuel systems for aircraft and vehicles even when using the same fuel. The system for vehicles would have smaller capacity and be equipped with vehicle nozzles rather than aircraft nozzles. Some airports converting to a single fueling sys- tem for aircraft and GSE may choose to decommission the current diesel system but leave the equipment in place as a backup, while others may choose to remove the equipment. 12

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TRB’s Airport Cooperative Research Program (ACRP) Report 46: Handbook for Analyzing the Costs and Benefits of Alternative Aviation Turbine Engine Fuels at Airports consists of the Alternative Fuel Investigation Tool (AFIT), a handbook on the use of AFIT, and a report on its development. AFIT is an analytical model designed to help airport operators and fuel suppliers evaluate the costs associated with introducing “drop-in” alternative turbine engine fuel at airports and the benefits as measured by reduced emissions.

AFIT, which is included in CD-ROM format with the print version of the report, takes into account options for using alternative fuel for other airside equipment, including diesel-powered ground support equipment.

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