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Updated analysis of the non-CO2 climate impacts of aviation and potential policy measures pursuant to EU Emissions Trading System Directive Article 30(4)

Lee, David and Arrowsmith, Steve and Skowron, Agnieszka and Owen, Bethan and Sausen, Robert and Boucher, Olivier and Faber, Jasper and Marianne, Lund and Fuglestvedt, Jan and van Wijngaarden, Lisanne (2020) Updated analysis of the non-CO2 climate impacts of aviation and potential policy measures pursuant to EU Emissions Trading System Directive Article 30(4). Research Report. European Aviation Safety Agency, Cologne, Germany.

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Abstract

13TASK3: Potential policy action to reduce non-CO2climate impactsFollowing a review of scientific literature, and expert workshop discussions, a range of potential mitigation measures were identified to reduce the non-CO2climate impacts of aviation7. Basedon various criteria in line with EU climate policy goals, the below six options were shortlisted to be considered in greater detail in terms of design, administration, incentives, caveats and constraints, and further research needs. These six options wereconsidered representative of similar considerations and details exhibited by an original longer list of options. Type of MeasureMain non-CO2effect(s) addressed by the measureFinancial1.NOXchargeNOX2.Inclusion of aircraft NOXemissions in EU ETSNOXFuel3.Reduction in maximum limit of aromatics within fuel specificationsSoot particulates and contrail-cirrus4.Mandatory use of Sustainable Aviation Fuels (SAF)Soot particulates and contrail-cirrusATM5.Avoidance of ice-supersaturated areasContrail-cirrus6.A climate chargeAll (NOX, water vapour, soot, sulphates, contrails) 1.NOXchargeThis measure is defined as a monetary charge on the total NOXemissions over an entire flight, approximated by certified Landing Take-Off (LTO) NOXemissions data, the distance flown and a factor accounting for the relation between LTO and cruise emissions.A legal analysis from 2009 suggested that neither ICAO’s Chicago Convention nor ICAO’s recommended policies on taxes and charges should prevent the implementation of such a measure. This option would incentivise engine manufacturers to reduce LTO NOXemissions during their engine design process, and airlines to minimise NOXemissions in operation, while taking into account associated trade-offs.Further research would be needed in these key areas:oUnder certain future scenarios of declining emissions of tropospheric ozone precursors from surface sources, combined with increasing aviation emissions, aviation NOXmay lead to a net negative climate forcing (i.e. cooling). As such, there is a need to monitor the scientific understanding of this issue as it further evolves over time.7These options would be in addition to those already in place, such as the aircraft engine NOXand nvPM emissions standard and airport NOXcharging schemes. 14oExisting analytical methods, such as the Boeing fuel flow method (BFF2) and the DLR fuel flow method, have been used in the past to estimate cruise NOXemissions based on LTO NOXdata. However, the robustness of these methods when applied to recent technological developments, such as lean burn staged combustion, is still being assessed and the methods may need to be updated. Research to develop and agree on an accurate, internationally recognised methodology for estimating cruise NOXemissions will be important for the implementation of this measure.oIn order to compare the climate change impact of NOXemissions to CO2emissions, an appropriate CO2equivalent emissions metric and time horizon would need to be agreed politically. In doing so, it is important to ensure that the trade-off between NOXand CO2emissions in engine design does not result in unintended consequences and a resulting net warming effect. oThe level of the charge should reflect the climate damage costs of aircraft NOxemissions. Using the aforementioned metric, these costs could be related to the damage costs of CO2, which are an on-going point of discussion.The necessary legislation and implementation of this option would need to be considered within the context of the regulatory framework of the Single European Sky Performance and Charging Scheme8, as well as other financial policy options (including those already in place).If the outstanding research issues linked to this measure are addressed, and there is the political will to take the option forward, then the measure could potentially be implemented in the mid-term (5 to 8 years)9.2.Inclusion of aircraft NOXemissions in EU ETSThe EU Emissions Trading System (ETS) is a ‘cap and trade’ scheme in which emission allowances for CO2emissions are traded among incumbent operators in a number of different sectors, including aviation. The system allows opt-ins for emissions of N2O and PFCs for stationary installations.This measure would see the extension of the scope of the EU ETS by incorporating aviation NOXemissions. As the EU ETS legislation uses the CO2equivalent emissions metric ‘GWP100’ to convert other greenhouse gases to CO2equivalents, it is assumed that including aircraft NOXinto EU ETS would also require using GWP100.This option would incentivise engine manufacturers to reduce NOXemissions during their engine design process, and airlines to minimise NOXemissions in operation, while taking into account associated trade-offs.Further research would be needed on the sameissues as the ‘NOXcharge’ measure.In contrast to other measures outlined in this report, this measure could be implemented by adjusting existing ETS legislation and building on existing administrative processes and 8COMMISSION IMPLEMENTING REGULATION (EU) 2019/317 of 11 February 2019 laying down a performance and charging scheme in the single European sky and repealing Implementing Regulations (EU) No 390/2013 and (EU) No 391/2013.9Rough estimates of timescales to implement policy options have been provided, but are dependent on addressing the identified research needs and the political will to take the options forward. For the purpose of this study, short-term is defined as 2-5 years, mid-term as 5-8 years and long-term as 8+ years. 15precedents (e.g. monitoring, reporting, verification and accreditation -MRVA; baseline; cap and auctioned allowances). The same EU ETS geographical scope for aviation could be applied to NOXas that for CO2emissions.The uncertainty about the climate impact of NOX, and the potential unintended consequences, introduces a political risk for the integrity of the EU ETS which needs to be taken into account when considering it as an opt-in non-CO2gas in the EU ETS. In this sense, the measure differs from the ‘NOx charge’.If the outstanding research issues linked to this measure are addressed, and there is the political will to take the option forward, then the measure could potentially be implemented in the mid-term (5 to 8 years).3.Reduction in maximum limit of aromatics within fuel specifications This measure would entail reducing the maximum volume concentration of aromatics within fuel uplifted at European airports.Lower aromatics in fuels provide a cleaner burn and reduced non-volatile Particulate Matter (nvPM) emissions, which are directly linked to contrail cirrus formation and radiative properties. In addition, the reduction in aromatics improves the energy density of the fuel, which reduces the mass of fuel needed for a specific flight and results in a small reduction in overallfuel burn / CO2emissions (approx. 1%).The aromatics concentration could be reduced through blending certain sustainable aviation fuels (SAF) with conventional Jet A-1 fuel, through hydro-treatment of Jet A-1 fuel or through changes in production processes by refineries.Jet A-1 fuel is the most commonly used aviation fuel in the world. Its fuel specifications are managed through the four main standardisation committees, including US ASTM (D1655) and UK DEF STAN (91-091). Engagement with these committees to discuss the climate benefits of low aromatic fuels will be crucial. This measure would require fuel producers to adapt their production processes to meet the new standard, which may result in higher CO2emissions in refineries. Further research would be needed in these key areas:oThe scientific understanding of the contribution of nvPM to the formation of contrail cirrus is evolving, but confidence level in the magnitude of the net positive climate forcing effect (i.e. warming) is low. As such, there is a need to monitor the scientific understanding of this issue as it further develops over time.oA cost-effectiveness assessment is needed to assess options for reducing the aromatics limit. While the maximum volume concentration of aromatics is 25 volumepercent, the actual content in Jet A-1 fuel currently used within the aviation sector is not well known. Studies have revealed that it can vary extensively. As such, the specifications of fuels being used in Europe will need to be monitored in order to beable to assess the impact of a reduced maximum limit of aromatics. oSpecial consideration will need to be given to the effect on military aircraft, which can be relatively old compared to commercial aircraft, and theuse of lower aromatics fuels may have airworthiness consequences for parts of the engine (e.g. rubber seals) where the fuel supply is shared. For this reason, ASTM and DEF STAN are currently considering an 8% minimum aromatics limit for fossil based fuels, though this is currently just guidance. 16oA system to monitor the aromatics content of fuels used in the aviation sector would need to be set up to ensure that the policy delivers the anticipated benefits.Existing fuel specification committees use a consensus-driven, technical approach. While a legally imposed EU standard would ensure a specific outcome, it would disrupt the current global approach to managing fuel quality standards.An alternative option to this measure could be an incentive for the sale of fuel with low aromatics.If the outstanding research issues linked to this measure are addressed, and there is the political will to take the option forward, then the measure could potentially be implemented in the mid-(5 to 8 years) to long-term (+8 years).4.Mandatory use of Sustainable Aviation Fuels (SAF)This measure would entail the mandatory use of SAF, for instance through an EU blending mandate specifying that a certain percentage of the total Jet A-1 fuel sold in Europe over a set time period would have to be SAF.Within the European regulatory framework, SAF would be defined as per the criteria in the new Renewable Energy Directive (RED II) 2018/2001/EU.SAF typically have lower aromatic concentrations and thus the same benefits as summarised in the ‘Reduction in maximum limit of aromatics within fuel specifications’ measure, as long as the aromatics content in the fossil part of the blend does not increase and offset the benefits. In addition, SAF also have lower lifecycle CO2emissions compared to conventional fossil based fuels and lower sulphur content resulting in lower SO4emissions.This measure would incentivise the use of SAF in the single market by providing certainty to SAF producers and an impetus to up-scale their production and benefit from economies of scale. It may also increase airline operational costs, depending on the size of the mandate and subsequent supply-side response from the SAF market.Further research would be needed in these key areas:oBlending mandates have already been introduced or announced inindividual European states. A cost-benefit assessment would be needed to inform a decision on the level of an EU blending mandate. This assessment would need to consider realistic yet ambitious levels, the impact on stakeholders and potential implementation processes (e.g. a dynamic blending mandate that increases over time in order to provide certainty to the market for long-term investments).oAs per option (3), a system to monitor the characteristics of SAF being used in operation within Europe would be needed to ensure compliance with the mandate and provide valuable oversight on the environmental benefits from this measure.A ‘control point’ will need to be identified (e.g. blending location), where the total SAF going to the aviation sector in Europe can be identified and hence compliance with the blending mandate can be monitored. This could build on existing legislation (e.g. RED II, FQD).The mandating of SAF results could be considered as a holistic approach with simultaneous reductions in CO2, nvPM and sulphur emissions, although it does not address NOxemissions. 17If the outstanding research issues linked to this measure are resolved, and there is the political will to take the option forward, then the measure could potentially be implemented in the short-(2 to 5 years) to mid-term (5 to 8 years).5.Avoidance of ice-supersaturated areasThis measure involves optimizing flight trajectories to avoid climate-sensitive regions, such as ice-supersaturated areas, in order to reduce the climate impact of aviation. This can be considered a potential first step towards full optimisation of flight profiles for climate impacts.Contrails are largely formed in ice-supersaturated and low-temperature areas, and thus avoiding these regions reduces contrail cirrus occurrence that have a net positive radiative forcing effect (i.e. warming).Prior to a flight plan being filed, Air Navigation Service Providers (ANSPs) and airline operators would need to have all the relevant information (e.g. temperature, humidity) in order to identify the ice-supersaturated areas. The route network would also have to be designed to allow such deviations based on this pre-flight tactical planning. Further research would be needed in these key areas:oA pilot project involving ANSPs,ICAO, meteorological institutes and airlines operating over the Atlantic would be needed to assess the feasibility and benefits of this measure. This should include the effect of such a measure on existing Single European Sky operational initiatives such as Free Route Airspace. Implementation over mainland European airspace would be a challenge as this region already faces capacity constraints during daily peak periods.oFlight detours (horizontal and vertical) to avoid ice-supersaturated areas are likely to have an impact on airlines in terms of costs, and will also lead to trade-offs with regard to fuel burn and emissions (e.g. CO2and NOX). An appropriate CO2equivalent emissions metric that permits a comparison between the climate change impact of contrail-cirrus and other aviation emissions will be required to determine the maximum detour that still ensures an overall reduction in climate impact from a flight. oMost of the contrail cirrus forcing that results in significant warming is believed to be due to a few large-scale events. It would therefore be advisable to ‘target’ flights that impact these events, rather than all flights. Identification of these few large-scale events should be a topic of further research as meteorological forecast models presently have only limited capability to predict persistent contrails correctly in time and space.Demonstration and communication on the environmental benefits would be needed, as well as potentially additional incentives, to ensure buy-in from stakeholders. If the outstanding research issues are addressed, including positive results from a pilot-phase project in the short-term, and there is the political will totake the option forward, then the measure could potentially be implemented in a more complete form in the mid-term (5-8 years). 186.A climate chargeThe concept of this policy measure is to levy a charge on the full climate impact of each individual flight. This makes it both the measure with the broadest coverage and the one that is likely to be the most complicated to implement. The introduction of a charge requires a good estimate of the climate costs at a flight level. Currently, there is no scientific consensus on the methodology to calculate these costs.It could be argued that a levy that aims to internalise the external costs would be considered a charge and not a tax. In this case, the charge would be related to recover the external costs of the climate impact of aviationFurther research would be needed on the same issues as the ‘Avoidance of ice-supersaturated areas’ measure, but with a larger geographical scope and including the level of the charge to be set for the climate damage costs of CO2, which is an on-going point of discussion.The necessary legislation and implementation of this option will need to be considered within the context of the regulatory framework of the Single European Sky Performance and Charging Scheme10. Significant more research is needed to develop and define this measure. If there is the political will to take this forward, then the measure could potentially be implemented in the long-term (+8 years).10COMMISSION IMPLEMENTING REGULATION (EU) 2019/317 of 11 February 2019 laying down a performance and charging scheme in the single European sky and repealing Implementing Regulations (EU) No 390/2013 and (EU) No 391/2013. 19CONCLUDING REMARKSThe latest scientific understanding on the climate change effects of non-CO2emissions from aviation activities has advanced over the last 10 years. While uncertainties remain with regard to these impacts, and how to assess them in terms of CO2equivalent emissions metrics, there are a rangeof policy options with associated pros and cons that the European Commission could evaluate. Specific research issues, which are identified this report, would need to be addressed in order to take these options forward.

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