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 24 CHAPTER 4: CASE STUDY ALTERNATIVE FUELS This chapter discusses the methodology used to select the alternative fuels for the scenarios discussed in Chapters 5 and 6 and in Appendices D and E. The alternative fuels were selected using a multi-criterion screening process, heavily weighted toward the fuel’s potential to reduce PM2.5 • Aircraft (main engines, excluding piston-engine aircraft) emissions from the major contributors identified in the base case results in Chapter 6 and Appendix E. These major contributors were identified as: • APUs • GSE and other specialized vehicles • Road vehicles The alternative fuels are representative of various chemistries (e.g., low-sulfur, low-aromatic feedstocks) and the ACRP 02-23 project considered the suitability for use, the likelihood of short-term (i.e., fewer than 10 years) commercial availability and the potential for life-cycle environmental improvement. For aircraft engines, the fuels have been limited to fuels which can be used in existing engines (i.e., drop-in fuels). Appendix C also discusses other potential challenges in implementing alternative fuels that have been taken into consideration. EVALUATION AND SELECTION PROCESS Summary of Methodology The U.S. Department of Energy (DOE) (1992) defines the following alternative fuels for vehicles (i.e., road and off-road such as GSE) under the Energy Policy Act (1992): • Biodiesel • Electricity • Ethanol • Hydrogen • Methanol • Natural gas • Propane Several emerging fuels are under development and are also regarded by DOE as alternative fuels. These include biobutanol, biogas, biomass-to-liquids (BTL), coal-to-liquids (CTL), FT diesel, gas-to-liquid (GTL), hydrogenation derived renewable diesel, P-Series, and ultra-low-sulfur diesel. The scope of the ACRP 02-23 project, as stated above, was limited to fuels with short-term commercial availability. In addition, the calculations of emissions are dependent on suitable emission data being available for the alternative fuel. These data also tend to be limited to those fuels that are available now, albeit in low volumes, rather than emerging fuels. Therefore, in terms of road vehicles and GSE, the alternative fuels under consideration were: biodiesel, electricity (for which the analysis assumed zero emissions), ethanol, hydrogen (for which the

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 25 analysis assumed zero emissions and, therefore, equivalent in terms of particulate matter to electricity), methanol (for which the analysis assumed zero emissions and, therefore, equivalent in terms of particulate matter to electricity, although in theory there are likely to be some volatile emissions), and gas (e.g., CNG and LPG). The majority of existing research into alternative aviation fuel has been related to jet fuel, which is used in turbine powered aircraft and APUs. At present, only blends of up to 50/50 FT and 50/50 HRJ (i.e., up to 50% alternative fuel with at least 50% conventional fuel) have been approved and it is likely that only blends will be approved in the short-term (e.g., fewer than 10 years). In the ACRP 02-23 project only the maximum (i.e., 50/50) blend allowed was considered. As discussed in Chapter 2 and Appendix A, a number of fuels for the main contributors were identified for further consideration. Aircraft Main Engine and APU: • Low-sulfur (or near-zero sulfur) Jet-A equivalent aviation fuel for aircraft main engines and APUs • FT synthetic fuels (50/50 blends) derived from coal, natural gas or biomass and blended with Jet-A for use in aircraft main engines and APUs • HRJ fuels (50/50 blends) derived from biomass and blended with Jet-A for use in aircraft main engines and APUs • Grade 91/96UL AvGas for piston-engine aircraft APU: • Fixed electrical ground power (at gates) to replace some APU use (some APU use will always be necessary, e.g., for main engine starts) GSE: • Electrically powered vehicles • LPG and CNG • Low-sulfur diesel • Ethanol blends E5, E10, E15, and E85 • Biodiesel blends B5, B10, B15, B20, and B100 Road Vehicles: • Electrically powered vehicles • Ethanol blends E5, E10, E15, and E85 • Biodiesel blends B5, B10, B15, B20, and B100 • Natural gas for road vehicles The criteria used for assessing which of the above alternative fuels and source combinations should be included are outlined in Table 4, followed by a description of the screening process and the results. A more detailed discussion of each criterion is presented in Appendix C. Each combination of alternative fuel and emission source was assessed in terms of each criterion’s rating (e.g., High (H), Medium (M), Equivalent (E), Low (L), Yes (Y) or No (N)). For example, FT jet fuels, compared with JP-8 conventional fuel, have particulate matter emission reductions that fall in the range 25% to 75% and, therefore, “Change in PM2.5 Emissions” for this fuel and source combination has been classed as “M.” Most of the criteria determinations

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 26 were based on expert knowledge and professional judgment, with the exception of “Change in PM2.5 Emissions” and “Cost of fuel relative to conventional.” “Change in PM2.5 Table 4 – Alte rna tive Fuels Matrix – Crite ria and Defin itions Emissions” data are based on the literature review (Chapter 2 and Appendix A) and specific sources are cited in the text in this Chapter. “Cost of fuel relative to conventional” is primarily based on the U.S. DOE fuel prices report (U.S. DOE, 2011). Criterion Definition Rating Change in PM2.5 (H, M, L) emissions The relative decrease in emissions compared with the dominant existing fuel/engine (or vehicle). H = More than 75% reduction M = Between 25% and 75% reduction L = Less than 25% reduction Availability of fuel (H, M, L) Is the fuel currently available? H = Widespread availability of fuel/blend in many states, though some regional variability M = Frequently available, but not at all sites/locations and would often require additional infrastructure (e.g., tanks) L = Limited/not readily available Availability of new vehicles (H, M, L) Are vehicles that can use this fuel currently available or are they likely to be available in the short-term? It should be noted that model availability depends on purpose. H = Many model types readily available for this fuel type and many being used M = Many model types available that can use this fuel, though not universal L = Not many models available (if any) that can use this fuel Cost to convert existing vehicles (H,M,L) How much is it likely to cost to convert a typical vehicle? H = More than $20,000 M = Between $200 and $20,000 L = Less than $200 N/A = no cost associated (i.e., for drop-in fuels) Drop-in fuel for existing vehicle? (Y/N) Can the fuel be used in existing vehicles with no modification? Y/N or N/A GHG life-cycle emissions (H, M, L) GHG emissions of the alternative fuel relative to the primary conventional fuel. This figure includes the fuel processing (i.e., “well to wheel”) emissions. H = More than 90% of conventional fuel M = Between 40% and 90% of conventional fuel L = Less than 40% of conventional fuel Emission data source reliability (H, M, L) Is the source of the proposed emission factors based on reliable data? H = Widely tested, many high-quality (government or referred journal) published studies with similar results for a range of vehicles M = Published studies, but limited to one or two vehicles L = No specific data, assumptions based on similar source (e.g., road vehicle for GSE) or based on calculations Cost of fuel compared with conventional (H, E, L) This is the marginal increase in fuel cost compared with the dominant existing fuel. H = More than 125% of conventional fuel E = Equivalent price to conventional fuel – between 75% to 125% of conventional fuel L = Less than 75% of conventional fuel (N/A where no data on cost are available. Variable and N/A assume worst case, high cost)

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 27 Criterion Definition Rating Cost of vehicles compared with conventional (H, M, L) This is the marginal increase in vehicle cost compared with the dominant existing vehicle type. H = More than 200% M = Between 110% and 200% L = Less than 110% N/A = no additional cost (i.e., for drop-in fuels) Additional infrastructure needed (H, M, L) What additional infrastructure is needed for the fuel to be used? H = Additional equipment such as compressors, high pressure buffers and tanks needed M = Additional tanks, similar to those already in existence, would be needed (e.g., for different blends) L = Assumes that diesel, electricity and gasoline are readily available on, or near, the site N/A = no additional cost associated Warranty validity issue (Y/N) Could the use of this fuel result in vehicle/engine warranty being invalidated? Y/N Note that “vehicle” is used here to refer to aircraft, APU, GSE and road vehicles Table 11 in Appendix C presents the results of the assessment of each fuel and source combination based on the ratings shown in Table 4 above. The H/M/L ratings were then converted into numerical scores between 0 and 3, where 3 related to the best ranking and 0 to the worst. For example, for “Change in PM2.5 Emissions”, where a high decrease in emissions is desirable, H was awarded a score of 3, M = 2, L = 1, and N/A = 0. Conversely, for “Cost to convert existing vehicles”, H was awarded a score of 0, M = 1, L = 2 and N/A = 3 because a high cost is less desirable than no cost. The primary aim of this ACRP 02-23 project was to assess potential reductions in PM2.5, in terms of emissions and impact. The use of the different criteria, in the context of this project, was to determine which fuel and source combinations to assess further, in terms of PM2.5 emission and impact reductions at the case study airports. Therefore, these scores were summed based on a weighted total score, where 45% of the total was allocated to “Change in PM2.5 Emissions” and the rest evenly distributed among the other criteria (i.e., 5% per criterion), with the exception of “Emission Data Source Reliability”, which was allocated 10%. The total scores were then converted to a percentage by dividing by 300. The consequence of this methodology was a significant bias towards those fuels where the PM2.5 emission reduction is likely to be significant compared with the primary conventional fuel. For example, source and fuel combinations resulting in PM2.5 reductions of more than 75% automatically had a total 45% scoring before any other criteria were considered. Those fuel and sources where either the final weighted result was less than 50% or the “Change in PM2.5 Table 5 Emissions” criteria was assessed as low or not applicable (i.e., a score of 1 or 0), were then discarded. This resulted in a list of the initial fuel and source combinations as shown in . When a particular airport is assessing whether a particular alternative fuel should be taken forward, they should not necessarily use the weightings used in the ACRP 02-23 project. Instead, they should consider their own business priorities to determine the most appropriate weightings for their own context. The “pre-weighted” information is provided for airports’ use in Appendix C, and separately in the Guidance Document.

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 28 Table 5 – In itia l Fue l and Source Combina tions Fuel and source 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, where available LPG GSE replacing diesel GSE, where available CNG GSE replacing gasoline GSE, where available CNG GSE replacing diesel GSE, where available E10 in gasoline-fueled GSE B100 in diesel-fueled GSE Natural gas road vehicles to replace diesel Electric road vehicles E10 in gasoline-fueled road vehicles E15 in gasoline-fueled road vehicles B100 in diesel-fueled road vehicles SELECTED CASE STUDY ALTERNATIVE FUELS As E10 and E15 are likely to produce similar reductions in PM2.5 As B100 is the only biodiesel blend included in emissions, it was decided to include only one of these fuels. E15 was removed from consideration as it is more costly to convert GSE and road vehicles to run on this type of fuel, and the data are not as reliable. Table 5, B20 was included in the list of fuels for analysis, even though the potential change in PM2.5 emissions was low compared with conventional diesel. There is a greater availability of vehicles that can use B20 compared with those that can use B100.

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 29 Table 6 lists the final alternative fuels and sources referred to in Chapters 5 and 6. Tab le 6 – Fina l Fue l and Source Combin a tions Fuel and Source 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, where available LPG GSE replacing diesel GSE, where available CNG GSE replacing gasoline GSE, where available CNG GSE replacing diesel GSE, where available E10 in gasoline-fueled GSE B20 in diesel-fueled GSE B100 in diesel-fueled GSE Natural gas road vehicles to replace diesel Electric road vehicles E10 in gasoline-fueled road vehicles B20 in diesel-fueled road vehicles B100 in diesel-fueled road vehicles The following points should be noted: • The fuels listed in Table 6 may only apply to sources that have a small impact on total particulate matter emissions at a particular airport and, therefore, the relative change in total emissions and air quality impact will be minimal. • HRJ fuels for aircraft were not included due to a lack of relevant emission data. However, as noted in Appendix C, since FT and HRJ fuels have similar structures, it is likely that the relative changes in emissions will be of a similar order of magnitude for aircraft. • There is uncertainty with regard to the emission factors for natural gas for road vehicles, which could result in higher emissions than would be expected. Again, this is discussed further in Appendix C.