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

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

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