Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports (2012)

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Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports viii ABSTRACT This report documents the findings of the ACRP 02-23 project undertaken to investigate the impact that alternative fuel use could have on emissions and ambient air pollution concentrations of fine particulate matter (PM2.5) at airports. The results are based on modeling of emissions and ambient air pollution concentrations at five case study airports for those sources that contribute most to PM2.5 emissions. Alternative fuels were selected for analysis primarily based on their potential to reduce PM2.5, and were limited to those with short-term (i.e., fewer than 10 years) commercial availability and available emissions data. The largest emission reductions occurred when alternative jet fuel was used in aircraft and auxiliary power units (APUs). This was followed by: replacing diesel-fueled ground support equipment (GSE) with GSE powered by electricity, fueled by liquefied petroleum gas (LPG), or fueled by compressed natural gas (CNG); gate electrifications; and replacing GSE diesel with biodiesel. In terms of air quality impact, the highest air pollution impact reductions generally occurred when diesel-fueled GSE were replaced with electric, LPG or CNG equivalents, followed by alternative jet fuel use in aircraft and APUs, replacing GSE diesel with biodiesel, and gate electrification.

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 1 EXECUTIVE SUMMARY This report presents the findings of the ACRP 02-23 project undertaken to investigate the impact that alternative fuels could have on reducing emissions and ambient air pollution concentrations of fine particulate matter with a diameter of less than 2.5 micrometers (PM2.5 Literature Review ) at airports. The ACRP 02-23 project consisted of reviewing published studies concerning particulate matter emissions and then modeling the effects of various alternative fuels on actual case study airports. The case study airports reflected locations where existing information was available to facilitate this research and represented different activity levels, meteorology, climate, geography, and demographics. Using these case study airports as a basis, an evaluation was then conducted of the effects of alternative fuels on particulate matter emissions from airport-related sources. A comprehensive literature review of information and data from over 200 national and international references was undertaken. This literature review, as reported in Chapter 2, was used to inform the data collection requirements for the ACRP 02-23 project and to underpin the development of the methodology. Only a small number of PM2.5 A significant amount of research has been conducted into the use of alternative aircraft fuels: measurement (monitoring) campaigns have been carried out at airports. These measurement efforts indicate that while airport sources may be contributing to local emissions, the overall impact diminishes rapidly as distance from sources increases. With respect to aircraft emissions, the literature review found that very few aircraft have reliable particulate matter emission data. Due to these data limitations, First-Order Approximation (FOA) methods were developed by ICAO/CAEP to enable particulate matter emissions for aircraft to be calculated. • Commercial airlines have tested alternative fuels blended with Jet A-1 on a limited number of overseas flights. • • Large reductions in aircraft PM2.5 emissions are possible with the newer alternative fuels that are suitable for aircraft use. The entire fleet of U.S. Air Force (USAF) aircraft is expected to be certified to use blended alternative fuels by 2016. A variety of different alternative fuels can be used for ground support equipment (GSE), and the Federal Aviation Administration (FAA) Emissions and Dispersion Modeling System (EDMS) already includes emissions factors for GSE operating on liquefied petroleum gas (LPG), compressed natural gas (CNG), and electricity. Possible alternative fuels for road vehicles include gasoline and ethanol blends and fossil diesel and biodiesel blends. Case Study Airports In parallel to the literature review, a review of data availability and willingness of U.S. airports to participate as case studies was undertaken. As discussed in Chapter 3, five case study airports were selected for inclusion in the ACRP 02-23 project: • Hartsfield-Jackson Atlanta International Airport (ATL)

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 2 • Las Vegas McCarran International Airport (LAS) • Manchester-Boston Regional Airport (MHT) • Philadelphia International Airport (PHL) • San Diego International Airport (SAN) Identifying Suitable Alternative Fuels The alternative fuels for the ACRP 02-23 project were selected using a multi-criterion screening process, which is outlined and discussed further in Chapter 4. A wide range of criteria were considered including: • Change in PM2.5 • Availability of fuel emissions • Availability of new vehicles • Cost to convert existing vehicles • Whether the alternative fuel is a drop-in fuel (i.e., it can be used in an existing vehicle) • Greenhouse gas (GHG) life-cycle emissions • Emission data source reliability • Cost of fuel compared with conventional • Cost of vehicles compared with conventional • Any additional infrastructure needed • Warranty validity issues Alternative fuels were considered for those sources that contribute most to PM2.5 emissions at airports. The selection process was heavily weighted toward the fuel’s potential to reduce PM2.5 The final selected case study alternative fuels and sources were: emissions, and limited to fuels with short-term (i.e., fewer than 10 years) commercial availability and those with available emission data. For example, hydroprocessed renewable jet fuel (HRJ) was initially considered, but was discounted due to the lack of appropriate emission data at the time of the ACRP 02-23 project. • Fischer-Tropsch (FT) (natural gas) aircraft • FT (coal) aircraft • 91/96UL AvGas for piston-engine aircraft • FT (natural gas) APU • FT (coal) APU • Electricity to replace some APU use • Electric GSE • Liquefied propane gas (LPG) GSE replacing diesel GSE • Compressed natural gas (CNG) GSE replacing gasoline GSE • CNG GSE replacing diesel GSE • Gasoline with 10% ethanol blend (i.e., E10) in gasoline-fueled GSE • Diesel with 20% biodiesel blend (i.e., B20) in diesel-fueled GSE • 100% biodiesel (i.e., B100) in diesel-fueled GSE • Natural gas road vehicles to replace diesel road vehicles • Electric road vehicles

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 3 • E10 in gasoline-fueled road vehicles • B20 in diesel-fueled road vehicles • B100 in diesel-fueled road vehicles Methodology A methodology to establish the base case PM2.5 emissions and local PM2.5 pollutant concentrations at each case study airport was developed. This methodology is discussed in detail in Chapter 5. The alternative fuel scenarios were then generated to assess the relative change on a number of key indices representing the impact that each alternative fuel and source combination would have on PM2.5 emissions and local PM2.5 In terms of road vehicles, the alternative fuel scenarios were considered only for on-airport roadways and parking (i.e., those under airport control and ownership). pollutant concentrations at each case study airport. Additional emissions from alternative fuel distribution emissions (e.g., tanker trucks carrying alternative fuels) were not included in the analysis. Instead, only the relative change in the emissions for the same source activity levels was considered. It is not always feasible for all emission sources of a particular type to use one particular alternative fuel. Therefore, penetration factors were applied to scale the emissions for each alternative fuel and source type. EDMS does not typically include PM2.5 emission results for piston-engine, turboprop, and turboshaft aircraft as there are no FAA accepted emission factors for these aircraft. During the development of the emissions calculation methodology used in the ACRP 02-23 project, it was found that more than 50% of the aircraft operating at some of the case study airports were of types for which EDMS does not estimate PM2.5 Base Case Results emissions. For this reason, a number of alternative methodologies were used to estimate emissions for these types of aircraft. A sensitivity analysis of the impacts of these methodologies upon aircraft emissions was conducted. For those aircraft where there is no appropriate alternative calculation methodology, emissions were scaled based on the average emissions for that aircraft size. The purpose of the base case was to have a foundation against which to determine the benefits of the alternative fuels. However, the base case also provides valuable information that may assist airports with focusing their particulate matter emissions efforts. The base case results are discussed further in Chapter 6 and Appendix E. The PM2.5 emissions inventories developed for the five case study airports indicate that aircraft (taxi, approach, takeoff, and climb-out) contribute the greatest percentage of PM2.5 emissions with GSE, APUs and road vehicle sources (on-airport and off-airport roadways, curbsides, and parking facilities) individually contributing to a much smaller extent generally for the case study airports. Stationary sources (e.g., boilers, generators, and fire training) generally contribute only a very small percentage to total airport PM2.5 emissions. Aircraft-related emissions are largely a function of the types and sizes of aircraft operating at each airport, airfield taxi and delay time, and meteorological conditions. GSE emissions are mostly a function of equipment type, fuel type, engine size, equipment age, and operational hours. Diesel-fueled GSE tends to emit higher levels of PM2.5 than gasoline-fueled GSE. APU emissions are a function of the presence of gate

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 4 power and pre-conditioned air, both of which reduce APU operating times. Road vehicle emissions are determined by traffic volumes, travel distances, and emissions factors. In turn, road vehicle emissions factors are dependent on regional emissions controls, vehicle speed, and meteorological conditions. The summary graph of EDMS-generated emissions, shown in Figure 1, depicts the emission sources at each airport. The emissions inventories developed for the five case study airports indicate that aircraft movements account for between 41% and 63% of total airport PM2.5 emissions, depending on the airport. GSE accounts for between 5% and 37% of airport emissions. APUs account for between 9% and 22% of total airport PM2.5 emissions, and road vehicles account for between 1% and 5% of total on-airport PM2.5 emissions. Figure 1 – On-Airport Ann ual PM2.5 (a) The PHL analysis year was 2004 and included a disproportionate amount of diesel GSE compared to other airports, since 2004 PHL has implemented a number of alternative-fueled GSE replacements, and, therefore, the GSE analysis is not a true reflection of PHL in recent years. Emis s ions Inven tory b y Source Category (kgs ) EDMS does not typically include PM2.5 If the sensitivity analysis is discounted, aircraft at all case study airports are still the dominant source of PM emission results for piston-engine, turboprop, and turboshaft aircraft as there are no FAA accepted emission factors for those aircraft. Therefore, those aircraft were considered separately as part of the sensitivity analysis. Results from the sensitivity analysis indicate that, at the case study airports, aircraft emissions could be more than 17% higher than reported by EDMS. The issue of particulate matter emissions from piston- engine, turboprop, and turboshaft aircraft is more of an issue at smaller airports with a higher proportion of general aviation. 2.5 emissions. It should be noted that a large proportion of the aircraft emissions occur above the ground during the landing and takeoff (LTO) cycle and have little impact on ambient air pollution concentrations at a local level.

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 5 In terms of ambient air pollution, the results were calculated for averaging periods that reflect the National Ambient Air Quality Standards (NAAQS) for PM2.5 (i.e., the annual average and the 98th percentile of the 24-hour average). Emissions from jet aircraft (taxi and takeoff), APU, GSE, roadways, and parking lots contribute most to ambient ground level PM2.5 annual average concentrations at locations with high air pollution levels from the airports. A similar general conclusion can be drawn for the 24-hour 98th Impact of Alternative Fuel Scenarios at Case Study Airports percentile results. The alternative fuel scenarios are presented in Chapter 6 for the EDMS-generated results for each isolated scenario, in terms of percentage reductions for the annual average and 24-hour 98th • The total on-airport emissions. percentile, for the following key indices: • • The maximum distance from the airport to a threshold airport impact concentration level, termed the Radius of Influence (ROI). The ROI is defined as the distance that extends from the source (in this case, the airport reference point) to the farthest receptor distance at which the source has a concentration greater than a specific threshold for a given pollutant. The threshold level for the annual average is 0.3 µg/m The airport impact concentration at the location of the maximum airport impact concentration in the base case. 3 and for the 24-hour 98th percentile it is 1.2µg/m3 • The area in which the air quality impact from the airport is below the threshold level is referred to as the influence area. The threshold level for the annual average is 0.3 µg/m . 3 and for the 24-hour 98th percentile it is 1.2µg/m3 Figure 2 . summarizes EDMS-generated emission reductions totals for all on-airport emissions, based on the results for the case study airports, for each of the alternative fuel scenarios for the annual average. Figure 2 shows that the largest emission reductions are provided by the following (listed in descending order): • 100% of aircraft and APU use drop-in fuels (i.e., 50% blends of FT jet fuels from either coal or gas). • Replacing a 100% of GSE with available electric, LPG or CNG equivalents, especially diesel-fueled GSE. • Replacing 100% of diesel with B100 in GSE (though it should be noted that this could have implications for GSE in terms of engine warranty). • Reducing APU use by providing electric ground power and pre-conditioned air at 100% of gates. Emission reductions for other scenarios are relatively small. To demonstrate the impact on localized airport air quality, Figure 3 summarizes the change in influence area for annual air pollution impacts (again, for the EDMS-generated results and based on the case study airports). As GSE emissions can have a greater influence on localized air quality than other sources, the alternative fuel scenarios for GSE had the greatest effect on the airport influence area concentrations. Figure 3 shows that the largest reductions in annual average influence area are provided by the following (listed in descending order):

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 6 • Replacing a 100% of GSE with available electric equivalents. • 100% of aircraft and APU use drop-in fuels (i.e., 50% blend of FT jet fuels from either coal or gas). • Replacing a 100% of GSE with available LPG or CNG equivalents, especially diesel- fueled GSE. • Reducing APU use by providing electrical ground power and pre-conditioned air at 100% of gates. • Replacing 100% of diesel with B100 in GSE (though it should be noted that this could have implications for GSE in terms of warranty). The concentration reductions for other scenarios are relatively small. As EDMS does not typically include PM2.5 • Around 50% reduction when a blend of 50% FT (natural gas) is used in turboprop (including turboshaft) aircraft. emission results for piston-engine, turboprop, and turboshaft aircraft, these aircraft types were considered separately as part of the sensitivity analysis. The alternative fuel scenarios included FT (natural gas) jet fuel for turboprop and turboshaft aircraft and 91/96UL AvGas for piston-engine aircraft. For the five case study airports, the emission reductions for the specific aircraft type (compared with the base case) were: • Above 90% reduction when 91/96UL AvGas is used in piston-engine aircraft.

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 7 Figure 2 – Alte rna tive Fue l Scenario s vers u s Bas e Cas e – Percen tage Ch an ge of To ta l Airpo rt Emis s ions Note: The implied increase in emissions for the “100% CNG GSE replacing gasoline GSE, where model available” scenario is a theoretical modeling output related to the emission factor source data used, and is not likely to be observed in actual practice.

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 8 Figure 3 – Alte rna tive Fue l Scenario s vers u s Bas e Cas e – Percen tage Ch an ge of Annu al In fluence Area Note: The implied increase in emissions for the “100% CNG GSE replacing gasoline GSE, where model available” scenario is a theoretical modeling output related to the emission factor source data used, and is not likely to be observed in actual practice.

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 9 Conclusions In addition to the results discussed previously the key conclusions are summarized below: • As HRJ jet fuels have a similar chemical structure to FT fuels, the findings for FT jet fuels should be considered broadly applicable to HRJ jet fuels as well. • The findings for alternative fuel use in jet aircraft could be considered broadly applicable to turboprop and turboshaft aircraft. • The impact of gate-related emissions (i.e., mainly those from APU and GSE) have a limited impact on air quality away from the gate areas compared to other sources where the emissions are spread over a wider area, such as aircraft and road vehicle sources. • For GSE and road vehicles the best PM2.5 Recommendations emission reductions are gained when (in increasing order): gasoline, CNG, LPG, or electric vehicles replace diesel. The study of air pollution and, in particular, PM2.5 • The NASA AAFEX report was the primary source for the jet aircraft main engine and APU alternative fuel emission data. This NASA study was based on one jet engine and one APU. Further study is needed to understand the variation that the use of alternative fuels could have on other turbine engine types. around airports is not a static subject. During the course of the ACRP 02-23 project, a number of future sources of information, model developments and improvements were apparent. Therefore, the following recommendations for future study have been made based on this information: • Various alternative fuels for aircraft and non-aircraft sources of PM2.5 were considered and discarded for a variety of reasons. One of the primary reasons was lack of suitable PM2.5 emission data. As such, the ACRP 02-23 project could be updated when further, appropriate, alternative fuel PM2.5 emissions are available (e.g., from the various PARTNER and AAFEX II projects and the resulting database of PM2.5 • The FAA is in the process of developing the Aviation Environmental Design Tool (AEDT) combined noise and air pollution model, which will replace the FAA’s EDMS in the future. Similarly, EDMS incorporates MOBILE6.2, which has been superseded by the EPA’s MOVES model. The MOVES model is being developed to incorporate road and nonroad sources, as well as a number of alternative fuels. As such, it would be worth repeating the ACRP 02-23 research with these two models when they are complete. emission factors and from the various ACRP projects aimed at refining APU, brake and tire wear, and GSE emissions). • Further research is needed to quantify the impact that specific types of biofuel (by feedstock, blend and engine type) will have on primary and volatile (i.e., “secondary”) particulate matter emissions.