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 51 CHAPTER 7: CONCLUSIONS AND RECOMMENDATIONS OVERVIEW The ACRP 02-23 project was undertaken to assess the potential for using alternative fuels to reduce emissions and ambient concentrations of PM2.5 CONCLUSIONS at airports. The conclusions and recommendations from the ACRP 02-23 project are summarized in this chapter. For those interested in emission reductions the most applicable scenarios were (listed in descending order): • Aircraft and APU using drop-in fuels (i.e., FT fuels) • Replacing GSE with available electric, LPG, or CNG equivalents • Replacing diesel with biodiesel • Reducing APU use by providing electric ground power and pre-conditioned air For those interested in air quality improvements the most applicable scenarios were (listed in descending order): • Replacing GSE with available electric equivalents • Aircraft and APU using drop-in fuels (i.e., FT fuels) • Replacing GSE with available LPG or CNG equivalents • Reducing APU use by providing electrical ground power and pre-conditioned air • Replacing diesel with biodiesel For jet-fueled aircraft and APUs it can be concluded that FT jet fuels from coal and natural gas can provide substantial reductions in PM2.5 APU emissions can also be reduced by reducing APU use (e.g., by providing alternatives such as electrical ground power and pre-conditioned air and giving encouragement to use). However, the impact on air quality is not as substantial as it is limited to the gate area of an airport and has little impact beyond the perimeter fence. In terms of providing electrical gate power and pre- conditioned air, this is likely to need an initial high investment level, though grants through the FAA’s Voluntary Airport Low Emissions Program (VALE) can be obtained. emissions and impact. As HRJ jet fuels have a similar chemical structure this finding should be considered broadly applicable to HRJ jet fuels as well. ASTM has approved an alternative jet fuel specification in annexes to ASTM D7566 for FT and HRJ fuels blended with at least 50% conventional jet fuel. This means that, in theory, these fuels can now be produced and sold as a “drop-in” fuel for aircraft (i.e., no modifications are required to the aircraft to use this fuel). However, current availability is limited. For GSE the best PM2.5 emission reductions are gained when (in increasing order): gasoline, CNG, LPG or electric GSE replace diesel GSE. The cost of alternative fuels for GSE is typically either equivalent or slightly higher than conventional fuel, with the exception of the high-biofuel blends (e.g., E85 and B100), which are more expensive compared to conventional fuels. The

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 52 high-biofuel blends may also create problems in terms of warranty invalidation for GSE. Alternative-fueled GSE can be bought with assistance via the FAA’s VALE program. While retrofit technology is not the subject of this report, it could be advantageous to fit equipment (e.g., particulate matter traps) to existing GSE diesel engines given the uncertainties of particulate matter emissions and to be cost-effective. Where vehicle replacement is an option, electric GSE is better when compared with other alternative fuels in terms of reducing directly emitted particulate matter (U.S. FAA, 2010a). Around the world, electric vehicles are available as replacements for baggage tugs and belt loaders. A few other specialist airside electric vehicles have been tested and there are a few makes of electric aircraft push-back tugs. However, their relatively modest capacity suggests they would not be very flexible and unable to deal with larger aircraft. For road vehicles the best PM2.5 No consideration is given in the ACRP 02-23 project to alternative fuels for other airport sources of PM emissions reductions are gained when (in increasing order) gasoline, CNG, LPG, or electric vehicles replace diesel vehicles, but these savings are limited especially in terms of their air quality impact. The cost of alternative fuels for road vehicles is typically either equivalent or slightly higher than conventional fuels, with the exception of the high-biofuel blends (e.g., E85 and B100) which are more expensive compared to conventional fuels. The high-biofuel blends may also create problems in terms of warranty invalidation for road vehicles. There is a limit to the number of road vehicles that airports can influence beyond their own fleet. However, certain strategies, such as structured parking lot charges and taxi licensing, could help to encourage use of alternative fuels in road vehicles. 2.5, not listed above, such as heating plant and fire training, which generally are small in comparison to those sources discussed above. However, some airports may rely on oil- or solid- fueled power for heat generation. Oil and solid fuel plants can produce significant PM2.5 emissions, but stack heights are normally engineered to minimize local air pollution impact. Those airports that wish to replace oil or solid fuel plants could consider either natural gas or LPG plant as low PM2.5 The findings for alternative fuel use in jet aircraft could be considered broadly applicable to turboprop and turboshaft aircraft. For piston-engine aircraft, alternative AvGas fuel is not yet commercially available in the U.S., but it could be in the future. Therefore, a comparison was made between 100LL (the AvGas used in the U.S.) and 91/96UL, with 91/96UL producing emission reductions in the region of 90% compared to 100LL for piston-engine aircraft. emitting alternatives. KEY RECOMMENDATIONS 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 potentially promising future sources of information, model developments, and improvements were apparent. Therefore, the following recommendations for future study have been made based on this information:

Airport Cooperative Research Program Project ACRP 02-23: Alternative Fuels as a Means to Reduce PM2.5 Emissions at Airports 53 • 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.