Bijlage 3 CE_Delft_230219_Carbon_budget_aviation_Def.pdf

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decarbonized industrial processes or intra-EU transport would have to stop at the moment when all saved certificates are used. This seems to be a unlikely situation given the enormous consequences and risks.

ReFuelEU Aviation Regulation (blending obligation)

RED3

The main provision of the ReFuelEU Aviation Regulation is a mandatory blending obligation of Sustainable Aviation Fuels (SAF) in the fuel mix supplied at airports in the European Union13. The minimum share of SAF increases from 2% in 2025 to 6% in 2030, 20% in 2035, 34% in 2040, 42% in 2045 and 70% in 2050. In addition, a specific share of the fuel mix should comprise synthetic fuels: 1.2% in 2030, 2% in 2032, 5% in 2035 and progressively increasing to 35% in 2050 (EP, 2023). The types of SAF that are allowed to contribute to the blending obligation are renewable synthetic fuels, renewable hydrogen, certain categories of biofuels and recycled jet fuels produced from waste gases and waste plastic. Biofuels based on feed or food crops or derived from palm and soy materials are not considered sustainable, in line with the criteria of the RED (see below) (EP, 2023).

The revision of the Renewable Energy Directive (RED) includes a target for the use of renewable energy in the transport sector. Member States can choose whether they accept a binding target of 14.5% reduction of greenhouse gas intensity in transport from the use of renewables in 2030, or a binding share of at least 29% of renewables within the final consumption of energy in the transport sector by 2030 (Council of the EU, 2023b). Aviation is part of the transport sector, but Member States are free to decide what the contributions of the various transport modes to the target will be. Furthermore, the RED3 strengthens the sustainability criteria for biofuels and introduces a combined target for advanced biofuels and Renewable Fuels of Non-Biological Origin (RFNBOs)14. It requires a share of at least 5.5% advanced biofuels and RFNBOs in the renewable energy mix supplied to the transport sector in 2030, with a minimum of 1% RFNBOs (Council of the EU, 2023b).

To prevent tankering practices and the associated additional emissions, the Regulation includes the obligation for aircraft operators to ensure that the quantity of fuel uplifted at EU airports is at least 90% of the annually required aviation fuel (Council of the EU, 2023a).

This target should be assessed in conjunction with the ReFuelEU Aviation Regulation (see above), which includes a

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Airports that process small amounts of passengers or cargo are excluded from the obligations of the Regulation. In the original proposal, the limit was set at 1 million passengers or 100,000 tons of cargo annually. According to Council of the EU. (2023a). Council and Parliament agree to decarbonise the aviation sector. Council of the European Union. https://www.consilium.europa.eu/en/press/press-releases/2023/04/25/council-

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and-parliament-agree-to-decarbonise-the-aviation-sector/, this scope was altered during the negotiations, but at the moment of writing the final text of the Regulation was not available yet to check for changes of scope in this respect. 14 Mostly renewable hydrogen and hydrogen-derived synthetic fuels.

blending obligation of Sustainable Aviation Fuels (SAF) for the aviation sector in particular. Indeed, the Commission indicates that the ReFuelEU Aviation Regulation should be considered a special case of these RED provisions for the aviation sector (CE Delft, 2021). Looking at the blending obligation provisions, it can be easily concluded that when these are met, the combined target for advances biofuels and RFNBOs is automatically met as well in the aviation sector. Member States have to assure that this target will be achieved in all transport fuels collectively.

Energy Tax Directive (ETD) The revision of the ETD aims to bring it in line with the EU’s climate and energy policy objectives. To do so, it introduces different categories for energy products, such as fuels and electricity, and a ranking of these categories based on their environmental performance. Energy tax rates should, according to the proposal, follow this ranking by applying the highest rate to most environmentally damaging energy products and the lowest rate to clean energy products (CE Delft, 2021). Energy tax rates should, according to the proposal, follow this ranking by applying the highest rate to most environmentally damaging energy products and the lowest rate to clean energy products (CE Delft, 2021). In the context of this study, the most relevant provision of the revision proposal is the extension of the ETD scope to aviation and shipping. This means that the ETD revision would end the

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EU tax exemption on kerosene (see Text box 1). Over a period of ten years, the aviation fuel tax rate for intra-EU commercial, scheduled passenger flights would increase from zero to the minimum rate for motor fuels. For sustainable aviation fuels, the rate would be zero for the same transitional period and after that correspond to the minimum rate according to the ranking mentioned above (CE Delft, 2021). Application of a tax on aviation fuels for full freighter flights and for extra-EU flights is optional, to be decided on by the Member States. It would require separate bilateral agreements with those extra-EU states. As tax matters are a Member State competence in the EU, the ordinary legislative procedure, with co-decision by the Council and the European Parliament (EP), does not apply to the ETD. Instead, the EP only has the right to be consulted and the members of the Council have to vote unanimously, which renders a decision in the short term improbable.

Conclusions With the adoption of almost all legal proposals from the Fit for 55 package, aviation is now much more incorporated into the EU’s climate policy toolbox than before. The transport targets of the RED now include aviation and the blending obligation mandates the uptake of SAF. The ETS for aviation, although preceding Fit for 55, was significantly strengthened by the decision to phase out free allowances. On the other hand, the emission reduction associated with the decreasing cap of the ETS can still easily materialize in other sectors than aviation. This will become harder towards 2040, when the cap will approach zero. In the meantime, the ETD has not proceeded much in terms of decision-making. Therefore, at this moment in time only the SAF blending obligation (against the background of the related RED transport targets) seems well-placed to effectively reduce EU aviation emissions within the sector itself in the near future, but still in a limited way due to the relatively low mandatory SAF percentages up to 2030.

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Section Summary In the Luchtvaartnota, national emission targets for aviation have been established for 2030, 2050 and 2070, but these are not yet legally enshrined. The main instrument to reduce aviation emissions at the national level is the introduction of CO2 emission ceilings for

Dutch airports by 2025 at the soonest.

3.4

National climate policies for aviation

The coalition agreement of the current (outgoing) Dutch cabinet (Rijksoverheid, 2021) includes a number of policy plans on aviation: — sustainable aviation fuels should be stimulated, including through a blending obligation for bio-kerosene and through investments in the development and production of synthetic kerosene in the Netherlands; — the Dutch government supports the inclusion of kerosene into the ETD revision (see above); — flying over short distances will be discouraged, leading to emission reductions on top of those arising from the Fit for 55 package;

— within Europe, train transport should become a proper alternative to flying as soon as possible, in terms of both costs and time; — proposals in the framework policy document on aviation, Luchtvaartnota 2020-2050 (Ministerie van I&W, 2020) will be implemented, such as the recent increase of the passenger ticket tax and the introduction of the aviation CO2 ceiling for departing aircraft from Dutch airports. Proposals in the framework policy document on aviation, Luchtvaartnota 2020-2050 (Ministerie van I&W, 2020) will be implemented, such as the recent increase of the passenger ticket tax and the introduction of the aviation CO2 ceiling for departing aircrafts from Dutch airports. In the Luchtvaartnota, which was established under the previous government, the general long-term policies on aviation are outlined. It also adopts the 2019 Agreement on Sustainable Aviation15 , which was the result of a broad stakeholder involvement and includes relative CO2 emission targets for the Dutch aviation sector16: — in 2030, the emissions equal 2005 emissions; — in 2050, the emissions are maximum half of the 2005 emissions;

— in 2070, the emissions are zero. It is important to note that these emission targets have not been legally enshrined yet. The main (future) policy instrument for securing them is the introduction of the CO2 ceiling, as announced in the coalition agreement and formally decided by the cabinet in March 2023 (Minister van I&W, 2023a). On each of the ‘relevant’ airports17 in the Netherlands, a CO2 emission ceiling for departing international flights will be imposed for 2030, 2050 and 2070, with a linear emission decrease assumed between the different projection years. The exact design of the emission ceiling instrument is subject of current study by the ministry, allowing for the input from relevant stakeholders. It will enter into force in 2025 at the soonest. Another policy instrument that was included in the Sustainable Aviation Agreement and hence in the Luchtvaartnota was a target of a 14% SAF share in the fuel intake at Dutch airports in 2030, and 100% SAF in 2050. However, recently the European Commission indicated that it will not allow the Netherlands to impose a higher blending obligation

________________________________ 15

Akkoord Duurzame Luchtvaart. On the basis of fuel intake at Dutch airports. 17 All airports with international traffic should be included under the emission ceiling, but a 16

distinction is being made between the three airports with slot coordination (Schiphol

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Airport, Eindhoven Airport and Rotterdam The Hague Airport) and airports without slot coordination.

than the one required by the ReFuelEU Aviation Regulation (6% in 2030 and 70% in 2050, see above) (Loupatty, 2023). Other proposed measures included in the Luchtvaartnota may also affect the climate impact of aviation, apart from impacts in other areas such as noise or local air pollution. These include for instance a cap on the total number of flights allowed from Schiphol Airport, new generation airplanes, operational improvements and changes in the airspace design. The national emission targets and the emission ceilings apply only to CO2. However, attention for non-CO2 climate impacts of aviation is increasing and the Dutch cabinet is developing a policy framework to address these non-CO2 impacts as well. In a recent letter to Parliament (Minister van I&W, 2023b), the cabinet outlined this framework, centred on three different strands: 1) more research, for instance on the nonCO2 effects of different types of sustainable fuels; 2) efforts to strengthen policies on non-CO2 effects at EU and ICAO level and 3) enhancing national and international cooperation to bridge the gap between scientific insights and the day-to-day business of the aviation sector.

In a recent letter to Parliament (Minister van I&W, 2023b), the cabinet outlined this framework, centred on three different strands: 1) more research, for instance on the non-CO2 effects of different types of sustainable fuels; 2) efforts to strengthen policies on non-CO2 effects at EU

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and ICAO level, and 3) enhancing national and international cooperation to bridge the gap between scientific insights and the day-to-day business of the aviation sector. Section Summary The International Air Transport Association (IATA) has committed to achieve net-zero carbon emissions from flying operations in 2050. About 340 Mton of the projected 1.8 Gigaton CO2 emissions to be mitigated would be covered by CCS and offsets. The European aviation industry presented its own roadmap to realise this target in the Destination 2050 report. This roadmap is more ambitious than the IATA target as it projects to make use of carbon removals rather than offsets. The Science Based Target initiative (SBTi) supports companies in

setting their own emission reduction targets. Its current guidance for aviation is based on a pathway corresponding to global warming of ‘well-below 2 ºC’.

3.5

Sectoral ambitions

Apart from policy targets and instruments at the various levels of governance, the aviation sector itself has also formulated targets and policies with respect to emission reduction from international aviation.

IATA Fly Net Zero target The International Air Transport Association (IATA), the global trade association for airlines, adopted a resolution in 2021 committing itself to achieving net-zero carbon emissions from their operations in 2050 (IATA, n.d.). Note that this is one year earlier than ICAO did – see Section 3.2. In IATA’s own projections, the net-zero target, called Fly Net Zero, implies that in 2050 1.8 Gigaton of CO2 emissions need to be mitigated. IATA estimates that 65% of this reduction can be achieved by using SAF, 13% by applying new propulsion technologies such as hydrogen, and 3% by efficiency improvements. The remaining 19% (about 340 Mton) could be dealt with by carbon capture and storage (CCS, 11%) and offsets (8%) (IATA, 2021). IATA defines a goal for 2050 but does not explicitly take into account a specific path towards 2050 (cumulative emissions).

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Destination 2050 Earlier in 2021, the European aviation industry presented its own roadmap to reaching net-zero emissions from all flights within and departing from the EU, called Destination 2050. According to the Destination 2050 report (NLR & SEO, 2021), the EU aviation sector seeks to achieve this by reducing emissions with 92% and remove the remaining 8% from the atmosphere through negative emissions (carbon dioxide removals, CDR). Like IATA, Destination 2050 defines a goal for 2050 with specific requirements for the path that sets a limit to the carbon emissions (carbon budget). It is important to note that negative emissions are not the same as offsets, which are used under CORSIA and mentioned in the IATA scenario for achieving net-zero emissions. Contrary to offsets, negative emissions do actually remove carbon from the atmosphere and thus are able to physically compensate for emissions. To ensure this compensation is real and permanent, though, negative emissions need to fulfil several strict criteria (Tanzer & Ramirez, 2019). Furthermore, permanent carbon removal is not being applied yet at any significant scale as most available technologies are not yet technologically mature, are still very expensive per tonne of CO2 captured or cope with other types of uncertainties, such as limited availability of sustainable biomass (CE Delft, 2023).

Science Based Target initiative (SBTi) The Science Based Target initiative (SBTi) supports companies from different sectors with a clear-defined and science-based decarbonization pathway in order to reduce their emissions in line with the Paris Agreement (Science Based Targets, n.d.). Its guidance for the aviation sector was developed by the World Wildlife Fund (WWF) with support from the International Council for Clean Transportation (ICCT) and the Boston Consultancy Group (BCG) (Science Based Targets, 2021). It states that, to be in line with the Paris targets, the aviation sector should reduce average carbon intensity by ~35-40% between 2019-2035 or ~65% from 2019-2050. The methodology used in the guidance focuses on jet fuel emissions (WTW) and does not take into account ground operations. Currently, it does not take into account non-CO2 effects either and it is based on a global warming target of ‘well-below 2 ºC’. A 1.5 ºC pathway is under development (Science Based Targets, 2021). The SBTi approach is centred on companies submitting and communicating their own emission reduction target. It does not prescribe how the target should be achieved, although the guidance does provide possible elements of an emission reduction strategy. It only considers emission reductions and does not take into account carbon removals (Science Based Targets, 2021).

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The SBTi 1.5˚C (50% likelihood) interim pathway has approximately constant emissions until 2030. From 2030, it anticipates a drastic decline in CO2 intensity of about 10% per annum on average. This reduction is to be delivered by technological breakthroughs and massive use of SAF. With this approach it postpones urgently required action, as will be discussed in the next sections.

3.6 Conclusions In Table 1, an overview is presented of the targets and instruments directed at reducing aviation emissions at various governance levels, as described in the previous sections. Table 1 – Overview of the targets and instruments directed at reducing aviation emissions treated in the sections above Overview of targets and policy instruments for aviation at different levels of governance Agreement or instrument

Target

Legal status/actors

Scope

Remarks

Paris Agreement

Long-term temperature goal (2, preferably 1,5 ºC global warming)

Binding for all parties to the Agreement

All emissions

All aviation included in target, but mandatory NDCs only have to cover domestic aviation.

CORSIA

Carbon neutral growth from 2020

Binding for non-exempted Member States from 2027

All aviation emissions covered by CORSIA above CORSIA baseline

Based on offsetting of emissions. Instrument ends in 2035.

LTAG

Net-zero emissions in 2050

Non-binding

All aviation emissions

EU Climate Law

55% GHG emission reduction in 2030; climate neutrality in 2050

Binding at EU level

All domestic EU emissions, also departing flights are included

Targets do not apply at national level but all Member States should contribute their fair share.

ETS Aviation Directive

No (only in combination with stationary ETS)

Binding for airlines

Intra-EEA aviation

Reductions can also be realised in other sectors as ETS allowances are interchangeable; ETS cap will reach zero around 2040.

RED3

Transport target in 2030; RFNBO/advanced biofuels subtarget (5.5% of which 1% RFNBOs) in 2030

Binding for Member States

All transport fuels used in EU

For the transport target, Member States can choose between 14.5% GHG intensity reduction or 29% renewables. Member States can decide on the contribution of aviation to these targets.

Global level (Section 3.2)

European level (Section 3.3)

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Overview of targets and policy instruments for aviation at different levels of governance Agreement or instrument

Target

Legal status/actors

Scope

Remarks

ReFuelEU Aviation Regulation

SAF blending obligation of 2% in 2025 increasing to 70% in 2050

Binding for Member States/fuel suppliers

Aviation fuel uptake in EU, some exemptions

Energy Tax Directive (ETD) proposal

-

Binding for Member States (when implemented)

All energy products. For aviation fuel: mandatory for intra-EU passenger flights, optional for cargo and extra-EU flights.

Luchtvaartnota

In 2030, emissions equal 2005 emissions. In 2050; emissions equal half of 2005 emissions. In 2070, emissions are zero.

Non-binding

Departing flights from Dutch airports

Policy ambition, but not enshrined in law.

CO2 ceiling

No concrete ceilings yet

Binding (when implemented)

Departing flights from Dutch airports

Not yet translated into concrete emission ceilings for Dutch airports; only then the instrument would become legally binding.

IATA

Net-zero emissions in 2050

Non-binding

All aviation emissions

Offsets allowed.

Destination 2050

Net-zero emissions in 2050

Non-binding

All emissions from flights within and departing from the EU

Negative emissions (CDR) foreseen.

Science Based Target initiative (SBTi)

Global warming of well below 2 ºC

Non-binding

CO2 emissions from fuel (WTW)

The SBTi invites companies to formulate and communicate their own GHG emission reduction target. A 1.5 ºC pathway is under development.

In proposal phase, no agreement yet (and not expected in the short term). If adopted, Member States are required to apply a minimum tax rate on aviation fuel for intra-EU passenger flights.

National level (Section 3.4)

Sectoral level (Section 3.5)

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From this Table and what was covered in the previous sections, we can draw the following main conclusions: at the global level, the Paris Agreement is the main standard for climate policy. Although its scope includes all emissions, the inclusion of international aviation in its main instrument, the NDCs, is not mandatory. Instead, to reduce international aviation emissions, countries should ‘work through ICAO’.

become available from 2040, which would mean intra-EEA emissions should be zero by then, unless other ways of acquiring allowances would be available.

ICAO sets a target of carbon neutral growth for aviation from 2020, which means it only aims to mitigate additional emissions compared to 2020 levels. Even so, its main instrument, CORSIA, is not sufficient to achieve this target. In the first place because not all aviation emissions will be included in its baseline due to exemptions, and in the second place because it allows for carbon offsets to compensate for emissions. As offsets are not the same as carbon removals from the atmosphere, a true compensation of emissions is not guaranteed.

At the level of the Dutch government, emission targets for all departing flights have been set and a carbon ceiling for Dutch airports to implement these targets is in preparation, but none of this has been legally enshrined yet.

Although the EU does not apply a specific target for GHG emissions reduction in aviation, it regulates both intra- and extra-EU aviation through different policy instruments. At this moment in time, however, only the SAF blending obligation seems well-placed to effectively reduce EU aviation emissions within the sector in the near future, and still in a limited way due to the relatively low mandatory SAF percentages up to 2030. Under current legislation no new ETS allowances would

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Different sectoral initiatives have emerged at different levels, mainly directed at net-zero emissions in 2050, but none of them implies a legal obligation to reduce emissions.

All-in-all, partly because of the sector’s tendency to continue to grow, current climate policies at different governance levels seem insufficient to realise a reduction of emissions from international (and Dutch) aviation that would be in line with the Paris objectives.

4 Remaining CO2 budget for global and Dutch aviation 4.1

Figure 7 - Global CO2 emissions from energy combustion and industrial processes, 1900-2022

Introduction

Since 1900, global CO2 emissions per year have increased from 2 Gt in 1900 to 37 Gt in 2022 (see Figure 7). The increase was moderate in the first 50 years (6 Gt emissions in 1950) and increased during the last 70 years with a dip during the COVID19 pandemic and a fast recovery in the last two years. In the Paris agreement the overall objective was set to hold the global average temperature increase to well below 2 ºC above pre-industrial levels and to pursue efforts to limit this increase to 1.5 ºC. This implies that not only the increase in CO2 emissions has to be stopped, but the trend has to be turned into a fast decrease in global GHG emissions. In this chapter we answer the question: ‘Which CO2 budget in 2030 for global and Dutch aviation is in line with global warming of 1.5 ºC and well below 2.0 ºC?’

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Source: (IEA, 2023b).

In this chapter, first a qualitative description of the required development of the global aviation sector towards 2050 is presented. Afterwards, the remaining global CO2 budget is discussed. Different ethical frameworks are applied for the distribution of the remaining CO2 budget between sectors and countries resulting in the budgets for the global and Dutch aviation sector in 2030.

4.2

Aviation development towards 2050

In this section, it is assumed that global net-zero emissions in all sectors is reached around 2050. To assess what this would mean for the aviation sector, we first give a short description of the current situation. Afterwards, the final state of global net-zero emissions is described, which should be reached around 2050 depending on the exact global reduction path. Finally, the path towards 2050 is discussed, since the focus of this study is 2030.

Aviation current situation Currently, the aviation sector depends for almost 100% on fossil kerosene. Overall aviation contributed to 2.4% (TTW) or 3.7% (WTW) of global CO2 emissions in 2019. The difference between the Tank-To-Wing (TTW) and the Well-To-Wing (WTW) emissions is whether the energy that is required for the fuel production and distribution (Well-To-Tank emissions) are associated to the aviation or to the energy sector (for details see Text box 7). Despite efficiency improvements in aircraft technology and operations, the sector’s emissions have increased by 2.3% per year on average between 1990 and 2019, as growth in air travel demand outpaced efficiency

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improvements in aircraft technology and operations (IEA, 2023a). In addition to CO2, aviation emits NOx, sulphate aerosols, soot particles and water vapour on a cruise height of about 10 km. These emissions also occur at ground level from other sectors, but they only contribute to global warming at high altitudes due to chemical and physical processes. The two largest non-CO2 climate impacts of aviation come from contrail-cirrus formation and NOx emissions. The impact of non-CO2 depends, in addition to the emitted amounts, on the emission location (mainly altitude and latitude) and the actual atmospheric conditions (weather, day-time). In contrast to CO2, the time horizon of the non-CO2 effects is much shorter. The different timescales of the CO2 and non-CO2 effects make it difficult to compare the effects to global warming. The best estimate of the combined worldwide non-CO2 climate impacts of aviation is that in 2018, they were responsible for the same amount of radiative forcing as the cumulative CO2 emissions between 1940 and 2018 (Lee et al., 2021).

The main takeaways from the current situation in the aviation sector are: — aviation contributes to 3.7% of global CO2 emissions if emissions of fuel production and distribution are included; — energy demand is almost 100% fossil kerosene; — globally demand grows faster than efficiency improvements leading to an annual growth of CO2 emissions by 2.3% over the last three decades; — large non-CO2 climate impact of aviation.

Aviation 2050 situation The Paris agreement ambition to limit climate warming to 1.5 ºC requires net zero emissions around 2050. The ‘lower’ the temperature goal, the faster the decarbonization has to happen. Net zero emissions means that emissions and carbon sequestration have to be balanced from that date for the sum of all sectors. Due to the cumulative character of CO2 in the atmosphere, emission overshoots in specific sectors or periods have to be compensated by negative emissions in other sectors or different periods in time. It is expected that in the transportation sector some emissions remain in 2050, which require compensation from other sectors, for instance from agriculture or forestry. Still, transportation emissions would need to decrease by around 90% in 2050.

The goal of net zero emissions in 2050 for all sectors implies: — almost 100% clean energy generation; — complete and permanent compensation for remaining emissions (removal of storage); — sufficient clean energy, biomass and carbon storage for the decarbonization of all sectors worldwide. Text box 7 - Well-to-Wing (WTW) vs. Tank-to-Wing (TTW) emissions Fuel emissions can be associated with either fuel production or fuel combustion. Fuel production emissions are well-to-tank (WTT) emissions, while fuel combustion emissions are tank-to-wing (TTW) emissions. WTT and TTW emissions combines result in well-to-wing (WTW) emissions. For fossil kerosene the WTW emission is 3.203 kg CO2-eq./litre, with a 78% share for TTW and 22% for WTT (CO2emissiefactoren.nl, 2023). Solely considering TTW emissions means that the emissions associated with fuel production are assigned to the energy sector. The Science Based Target (SBTi) transport guidance prescribes that it is desired that scenarios are developed on a WTW basis (Science Based Targets, 2021). There are two key reasons for this: 1.

Including upstream production and distribution (WTT) emissions is required to credibly account for the use of Sustainable Aviation Fuels (SAFs).

2.

Inclusion of upstream production and distribution (WTT) emissions best captures emissions reduction from future alternative power plants, including those that consume electricity and hydrogen.

Sustainable aviation fuels (SAF) are either biofuels or synthetic fuels. The emissions related to the combustion of these fuels are comparable to fossil-based jet fuels, except for marginal efficiency gains. By far the majority of the emissions reductions are due to

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the production process. In order to take this into account the WTW emissions are assessed with a Lifecycle Analysis (LCA) approach, which includes feedstock recovery, fuel production, transportation at all stages of the chain and the fuel combustion in aircraft engines.

For the SAF production energy is required, for instance for biomass to be converted in biofuels. Currently, most energy is ‘grey’, produced using fossil fuels. Green energy is produced using renewable sources, thus no emissions are associated with this process. The 2050 goal is that all energy is produced using renewable ‘green’ sources. Only considering TTW emissions would not capture this shift from ‘grey’ to ‘green’ energy.

The majority of the generated energy will be produced by renewable sources as wind, sun and water, but biomass and nuclear energy will also play a certain role. Some energy might still be generated through fossil fuels, although volumes will decrease drastically and remaining emissions from fossil fuels must be compensated. Permanent and complete carbon sequestration is either done naturally by trees, plants or the ocean who capture CO2 from the air or by permanent carbon storage in the ground. Carbon storage is currently still challenging and expensive, which makes it an uncertain ‘solution’ (see Text box 5). Therefore, it is undesirable to completely rely on this and not take action to curb carbon emissions.

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The availability of sufficient clean energy has a large impact on the WTW emissions of SAF (see Text box 8). Assuming 100% green electricity, results in WTW emission reductions compared to kerosene of more than 95% for all SAF types (NLR & SEO, 2021). Synthetic fuels are produced using green energy and CO2 from the atmosphere or industrial processes. The carbon is first captured at the production phase – either through DAC or at industrial emitters - and later during combustion in the jet engine released in the atmosphere. Hence, the net emissions of synthetic fuels are zero. The same applies to biofuels. Biofuels are produced using (clean) energy and biomass. The biomass has captured the CO2 during the growing phase of the plant and that is released in the atmosphere during the flight. However, there a several arguments why biofuels are not entirely carbon neutral (see Text box 8). Text box 8 - Overview Sustainable Aviation Fuels (SAFs) Sustainable aviation fuels are developed to replace fossil kerosene, as they bring a significant emission reduction. The production or SAFs require feedstocks, which are either biomass feedstock or clean energy.

The following available or most promising SAFs can be distinguished: −

Hydro-processed esters and fatty acids (HEFA);

−

Fischer-Tropsch (FT);

−

Alcohol-to-Jet (AtJ);

−

Power-to-Liquid (PtL).

The first three are biofuels and the latter is a synthetic fuel. Biofuels are made from biomass or residues, in combination with (clean) energy. HEFA is commercially the most mature biomass for biofuel production. The main feedstock for HEFA are waste and vegetable oils – of which future availability is limited (see Text box 11) - in combination with (green) hydrogen (Becken et al., 2023). Currently, almost all hydrogen is produced using fossil fuels. In 2019, less than 0.1 % of all hydrogen was produced using clean energy, and thus labelled as green hydrogen (IEA, 2019). FT mainly uses agricultural and

The aviation sector is not the only sector which needs to decarbonize. All sectors require sufficient green energy, biomass and if necessary, carbon storage. As a consequence, these inputs are probably scarce in 2050 leading to competition between sectors for green energy and biomass. A more detailed explanation on the future availability of green energy and biomass is given in Text box 11.

forestry residues in combination with (clean) energy to produce biofuel (Becken et al., 2023). The AtJ process mainly uses sugarcane, corn grain and switchgrass and converts this to ethanol or other alcohol via fermentation (Becken et al., 2023). Synthetic fuels use captured CO2 – either direct air capture (DAC) or residual industry CO2 – and (clean) energy and through a chemical process this results in synthetic kerosene, hence no biomass is required. In essence, this process is the reverse of combustion.

The average current life-cycle CO2 savings for 2030 of the different SAFs compared to kerosene are (EU, 2018): −

HEFA: 65%;

−

FT and AtJ: 65%;

−

PtL: 85%.

As more clean energy becomes available and the share of green hydrogen increases in the future, the average life-cycle CO2 savings of all SAFs is expected to increase to 95% for biofuels and to 100% for synthetic fuels (NLR & SEO, 2021).As more clean energy becomes available and the share of green hydrogen increases in the future, the average life-cycle CO2 savings of all SAFs is expected to increase to 95 % for biofuels and to 100 % for synthetic fuels (NLR & SEO, 2021).

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Text box 9 – Are biofuels carbon-neutral? There is no consensus in science/literature whether biofuels, and to be more specific biomass, should be defined as carbon neutral (Becken et al., 2023). In essence, plant material (biomass) is not a clean energy source as it releases CO2 emissions when burned. However, plant growth is an ongoing process, subjected to the availability of land (or water for algae fuels). The emissions from burning biomass are in the past absorbed from the atmosphere during plant growth. The issue arises from the time lag between the carbon emissions and the equivalent amount being removed from the atmosphere and stored in new plants (biomass). Forest biomass is the most critical given the age of trees in natural ecosystems. The lag time is equal to the age of a feedstock. If the feedstock is from a 100-year-old tree, then the time lag is 100 years. It must however be noted that after 50 years, it can be assumed that a large part of the carbon is already sequestrated.

In addition, there will always be more CO2 in the atmosphere as long as biomass is burned (Becken et al., 2023). The net effect of accumulated atmospheric CO2 of biomass harvesting results in a permanent increase of atmospheric CO2 levels compared to a scenario where forests remain intact. In order for bioenergy to effectively decrease atmospheric CO2 levels, it must be guaranteed that the total emissions from growing,

processing, distributing and burning biomass are not larger than all alternative actions that would have happened to the biomass if it was not used as a green energy source. According to (Becken et al., 2023) it is therefore invalid to assume that biomass is carbon neutral.

Furthermore, it is argued that energy from renewable sources is not entirely carbon neutral (Becken et al., 2023). Energy-infrastructure is required for production and transport of this green energy. For instance, materials needed for the production of wind

to higher ticket prices and resulting in a deceleration of aviation growths. Reasons for the expected fuel cost increase are additional costs for fossil fuels for instance due to increasing CO2 pricing via the EU ETS and higher costs for SAF compared to kerosine. On the other hand, fuel costs will decrease due to efficiency improvements in aircraft technology and operations, resulting in lower ticket prices and thus accelerating aviation growth.

turbines or solar panels require scare materials and releases CO2 emissions during the manufacturing process of these sustainable energy technologies. The emissions are referred to as embodied emissions.

In 2050, offsets are infeasible since all countries and sectors need to reach net-zero emissions (see Text box 5). Examples of offsets are compensating aviation’s CO2 emissions by for instance planting trees or building new public transport in developing countries that replaces more CO2-intens transport. However, it is not guaranteed that the trees are not destroyed by wild fires or that the public transport would not have been built without the offsets. Hence, these kind of offsets do not guarantee CO2 reduction while at the same time they extract money from the aviation sector, which could also be invested in decarbonization of aviation. Worldwide demand of aviation is expected to increase significantly due to the expected worldwide economic growth. In addition, demand implications will occur due to changes in costs. On the one hand, fuel costs are expected to rise leading

43

230219 - Carbon budget aviation – January 2024

For the aviation sector specific, net-zero emissions in 2050 implies: — offsets for CO2 emissions are not possible since all countries and sectors need to reach net-zero emissions; — non-CO2 emissions require compensation; — remaining TTW emissions from fossil kerosene must be compensated by Carbon Dioxide Removal.

Aviation GHG emission pathway towards 2050 The remaining carbon budget towards the net-zero goal, has to be shared globally with all sectors, resulting in competition between aviation and other sectors for this carbon budget. This carbon budget is a total fixed budget for all years until 2050. High emissions in the next years automatically results in less carbon budget in the years further ahead, which makes it more challenging to reach net-zero in 2050. It thus requires

immediate action to decarbonize and reduce emissions in all sectors including aviation. To reach the goal of net-zero emissions in 2050, the aviation sector relies on SAFs to reduce their emissions. Scaling-up SAF production takes time. Even with historically high year-onyear growth rates of renewable electricity and green hydrogen production, and when DAC will be technically mature and ready to be scaled up, this takes decades (Bauen et al., 2020). Hence, the immediate scaling-up of biofuel production and pre-commercial development of the synthetic fuel production becomes imperative, as solely relying on depleting the remaining carbon budget and switching to SAFs overnight is impossible. Production of SAFs require green energy and biomass, but the aviation sector is not the only sector requiring green energy and biomass for its decarbonization. Demand for green energy and biomass will increase in the future, resulting in competition between sectors for these goods not only in 2050 but already in the next years. More information regarding the availability of clean energy and biomass is given in Text box 11.

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230219 - Carbon budget aviation – January 2024

Text box 10 – Hard-to-abate or Costly-to-abate Aviation is usually referred to as a hard-to-abate sector, meaning that GHG emissions from this sector are difficult to bring down. Although the projected global growth of aviation is not working to the advantage of quickly achieving absolute reductions, we want to clarify that emissions in the aviation sector are technically not hard-to-abate. Although there are initiatives for electric and hydrogen planes, or innovative aircraft designs as the flying V, which would reduce fuel consumption (TU Delft, 2023), using drop-in SAFs instead of fossil-based fuels will in fact do the job and is both easily applicable and technically proven. Bio-based SAFs are already being produced on a limited scale and e-SAFs have reached TRL 8, meaning that pilot plants have shown that their production is technically feasible (ITF, 2023). Almost all aspects related to aviation – airplanes, engines, airports, fuel infrastructure – only need moderate adaptions (technological and operational efficiency improvements) or can even be maintained in their current form. Only fuel production processes have to change and need significant scaling-up. In contrast, the decarbonization in other sectors is considerably more complex, as can be seen for instance in heating of residential houses.

The transformation from natural gas heating and cooking towards other alternatives often requires fundamental renovation to improve isolation, as well as installation of new stoves and heat pumps. The investment costs are however offset by the reduction in utility expenses, given that electricity proves to be cheaper than gas. In aviation, this is not the case since SAF production is more expensive than fossil kerosene. Hence, the ‘hard’ part is actually not technically hard but ‘costly’.

Text box 11 – Availability of clean energy and biomass

To understand the second point, it is important to realize that large energy losses occur

For the decarbonization, the aviation sector heavily relies on the shift from fossil fuels to

in the production chain of SAFs. At each stage there is energy ‘lost’ as heat waste

sustainable aviation fuels (SAFs). In the medium-term, these are mostly biofuels, while in

– for turning non-fossil primary energy into final energy for SAFs that delivers the required

the long-term the share of synthetic e-kerosene is expected to increase significantly.

energy density for aircraft engines. The ‘energy return to energy invested’ (EROI) is a

There are two essential components required to produce biofuels, (clean) energy and

ratio of the returned usable energy, to all the energy invested to make this useable

biomass. Synthetization of different (aviation) roadmaps shows that in 2050, the aviation

energy. EROIstandard indicates the energy content of the primary energy source and EROIfinal

sector could require 9% (20 EJ) of all global renewable energy and 30% (15 EJ) of the

indicates the energy content of the final energy carrier. The EROIfinal incorporates

worldwide available biomass energy (Becken et al., 2023) The increasing share of SAFs in

EROIstandard plus additional required energy to produce this final energy carrier. The EROI of

aviation could therefore be problematic for two reasons:

a fuel decreases when energy becomes more scarce and more difficult to produce or

1.

Biomass competes for land needed for nature-based carbon removal and other land

extract. The EROIstandard of oil is 20 and the EROIfinal of fossil jet fuel is 5.8.The EROIstandard

use.

of bioenergy for biogenic SAF lies between 3 and 4 for sugar cane and is less than for

Clean energy could be used more effectively to decarbonize other sectors.

others. The EROIfinal from biogenic SAF ranges from 1.64 of palm oil (HEFA) to 0.36 of

2.

sugarcane (AtJ). In the process of fuel conversion from bioenergy to SAFs between 9-60% The first point refers to land use implications associated with biomass. Food, municipal

of the energy is lost. For producing synthetic kerosene, more than half of the primary

and industry waste only delivers a fraction of the total volume of biomass needed. Energy

input energy is lost due to conversion and distribution. This increase to the order of 70% if

crops, agriculture and forest residues will become essential to meet the biomass demand.

the synthetic kerosene is used for propulsion.

Potential feedstocks for SAFs are: −

Energy crops: 5-10 EJ;

The aviation sector is not the only sector that requires clean energy and biomass to

−

Waste (food, municipal and industry): 5 EJ;

reduce its emissions, leading to the fact that clean energy is a scarce good. The fact that

−

Agricultural residues: 5-12 EJ;

the production of bio-SAF is energetically costly (EROIfinal values of around 1), raises the

−

Forest products: 10-20 EJ.

question whether there is a net climate benefit from a wider cross-sectoral perspective if around 9% of all clean energy is used for SAFs, where the majority of electricity is wasted

The latter three all have substantial impact on land use. In addition, for forest biomass there is a significant time lag in re-sequestering biocarbon, leading to a discussion whether it can be stated biofuels are carbon-neutral when produced using clean energy (see the textbox Are biofuels carbon-neutral? for more information).

45

230219 - Carbon budget aviation – January 2024

(Becken et al., 2023).

Conclusion — Aviation is a technically easy-to-abate but costly-to-abate sector. — Immediate scaling-up of biofuel production and pre-commercial development of the synthetic fuel production are essential. — High energy requirements in the SAF production chain and competition between sectors for sufficient green energy and biomass result in an allocation problem of these resources between sectors and countries. In the following section the allocation problem is discussed for different ethical frames.

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230219 - Carbon budget aviation – January 2024

4.3

Table 2 - Remaining CO2 budget mid-2023 and remaining number of years until the

Global GHG budgets

budgets are exhausted when the current worldwide emissions stay constant

IPCC has estimated remaining carbon budgets from the beginning of 2020 onwards for different temperature limits and probabilities that these budgets will limit global warming to the temperature limit. Table 1 - Estimated remaining carbon budgets from the beginning of 2020 in Gt CO2 Estimated remaining carbon budgets from the beginning of 2020 (Gt CO2)

50%

67%

83%

1.5 ºC 1.7 ºC

500

400

300

850

700

2.0 ºC

550

1350

1150

900

Source: (IPCC, 2022).

Today (mid 2023), 3.5 years later almost 130 Gt CO2 of the budget is already emitted to the atmosphere, 36.0 Gt in 2020 37.9 Gt in 2021, 36.8 Gt in 2022 and assuming half of 2022 emissions for the first half of 2023 (Crippa et al., 2021) (Crippa et al., 2022) (IEA, 2023b). As an illustration we have estimated the number of years that remain until the global GHG budgets are reached, if the current emissions stay constant (see Table 2).

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230219 - Carbon budget aviation – January 2024

Temperature increase (probability that limit is exceeded)

Remaining carbon budget (50% likelihood)

Remaining years with current emissions (36.8 GT per year)

1.5 °C (50%)

370

10.1

1.7 °C (66%)

570

15.5

Figure 8 illustrates the relationship between the temperature increase and the probability that this limit is reached for 4 carbon budgets, 400 Gt, 500 Gt, 850 Gt, 1,150 Gt. The 1,150 Gt budget has a probability of approximately 33% that the critical limit of 2 ºC will be exceeded. Since the Paris Agreement sets the goals to hold global warming well below 2 ºC and to pursue efforts to limit it to 1.5 ºC, this budget cannot be considered to be in line with the Paris agreement. The 400 Gt budget, seems to be out of reach given the fact that already 130 Gt have already been used in the last 3.5 years despite a reduction in global economic activities due to the COVID19 pandemic.

In the further analysis of this study two budgets will be considered in two scenarios: — 500 Gt budget scenario: has a 50% likelihood that global warming is limited to below 1.5 ºC and >83% for below 1.7 ºC. With this budget the temperature increase may be limited to 1.5 ºC and is likely to stay below 1.7 ºC. — 700 Gt budget scenario: has a 67% likelihood that global warming is limited to below 1.7 ºC and about 90% for below 2.0 ºC. With this budget the temperature increase may be limited to 1.7 ºC and is very likely to stay below 2.0 ºC. The extent to which this budget is Paris-aligned is debatable.

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230219 - Carbon budget aviation – January 2024

Figure 8 - Visualization of the relation between the global temperature increase and the probability that this limit is exceeded for four CO2 budgets. The markers correspond to original values from IPCC (see (IPCC, 2022)), the lines illustrate the trend for all probabilities between 17 and 83%.

4.4

Global aviation CO2 budgets

To determine the share of aviation from the remaining global carbon budget, the following scenarios have been considered: — constant share of aviation in global CO2 emissions from 2019 onwards; — share of aviation according to the carbon budget in the IEA Net Zero Emissions (NZE) scenario. Table 3 presents the share of aviation in the global carbon budget according to the different scenarios. Table 3 - Share of aviation in global carbon budget Share of aviation in global carbon budget

TTW emissions

CO2 emissions 2019

2.4%

IEA NZE carbon budget

3.9%

With these estimates a bandwidth for the share of aviation in the global carbon budget can be constructed. The lower end of the bandwidth would be equal to 2.4%, a constant scenario represented by the 2019 share of aviation in global CO2 emissions. The upper end of the bandwidth would be 3.9%, a growth scenario represented by the share of aviation in the IEA NZE carbon budget. The IEA scenario assumes

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230219 - Carbon budget aviation – January 2024

cost-efficient global decarbonisation, in which the less costlyto-abate sectors decarbonise first. This means that the share of aviation is allowed to grow with respect to other sectors. This principle of cost-efficient decarbonisation is also reflected in the global reduction targets, see Text box 12, in which the reduction targets for aviation are clearly lower. Based on this bandwidth the remaining global carbon budgets for aviation are estimated (see Table 4). The budgets vary between 12.0 Gt and 27.3 Gt. Note, that non-CO2 climate effects of aviation are not considered in these budgets. The main reason is that these emissions do not cumulatively add up, since their lifetime in the atmosphere is much shorter. Hence, they do not ‘eat’ the budget. However, non-CO2 emissions lead to global warming for a short period in time. During this period they increase the probability of reaching tipping points in global warming and to contribute to irreversible processes. Therefore, it is very important to develop efficient non-CO2 policies and to reduce them as soon and as fast as possible. In a net zero situation non-CO2 emissions have to be compensated for example by means of permanent carbon storage or carbon removal. For a detailed explanation see Annex A.

Table 4 – Carbon budget for aviation Global aviation carbon budget

50% 1.5°

66% 1.7°

(500 Gt)

(700 Gt)

Current share 2.4%

12.0 Gt

16.8 Gt

IEA NZE share 3.9%

19.5 Gt

27.3 Gt

Text box 12 – Aviation reduction compared to other sectors Every sector is required to reduce its CO2 emissions to achieve global net-zero in 2050. The reduction path in the IEA NZE scenario of the aviation sector is compared to other sectors here, to gain insight in the differences in the speed of reduction. The projected CO2 for 2050 and the percentage decrease compared to 2019 for all sectors is shown in Table 5. The comparison shows that the reduction targets are lower for the transport sector compared to other sectors and within transport the required reduction is the lowest for aviation, since aviation is costly-to-abate.

Table 5 – Aviation reduction compared to other sectors (IEA, 2021) Sector

CO2 emissions 2019 (Mt)

CO2 emissions 2050 (Mt)

% change

Electricity and heat sectors

13,821

-368

-102.7%

Industry

8,903

519

-94.2%

Transport

8,290

689

-91.7%

Road

6,116

340

-94.4%

Aviation

1,019

210

-79.4%

Shipping

883

122

-86.2%

3,007

122

-95.9%

Buildings

Subsector

________________________________ 18

50

Based on forecasts from the United Nations and CBS.

230219 - Carbon budget aviation – January 2024

4.5

Dutch aviation CO2 budgets

What is a fair share for Dutch aviation? This is a complex question, which cannot be answered satisfactory by purely weighing technical or economic arguments, since it implies ethical issues. It boils down to the question how uniform or heterogenous the budget should be distributed between global citizens. A starting point could be the current share of Dutch aviation of 1.16% of global aviation. This share would manifest the disproportional high amount of flights from Dutch citizens compared to population groups elsewhere. When the global budget would be distributed to countries by shares of the world population in the period of 2019-205018, the share of the Netherlands would be only 0.21%, thus more than a factor five less. However, this allocation method is very theoretical given the current differences in economic development and aviation activities between the countries of the world. It would allow the same aviation emission between today and approximately 2050 for individual persons in developing and developed countries. Given the fact that the population growth and economic growth is expected to be larger in other parts of the world than in the Netherlands, it is also expected that the aviation

sector grows faster in developing countries. Using forecasts for the socio-economic development of countries as a proxy leads to a share for the Netherlands of 1.05%. This share for the Netherlands is used for further analysis. Table 6 combines the global carbon budgets with the global shares of aviation and the Dutch share, leading to four carbon budgets for Dutch aviation. Table 6 – Dutch aviation carbon budget Dutch aviation carbon budget

50% 1.5° (500 Gt)

66% 1.7° (700 Gt)

Current share 2.4%

126 Mt

176 Mt

IEA NZE share 3.9%

205 Mt

287 Mt

Reflections on the budgets: — The ambition of the Paris agreement is to limit global warming to 1.5 ºC and to enforce warming well below 2 ºC. This fits best with a global budget of 500 Gt. As explained in Chapter 2, the physical impacts of a global warming of over 1.5 ºC may be disproportionally larger than that of 1.5 ºC due to tipping points. To not risk overshooting this level of global warming, the Netherlands, being one of the wealthiest nations on Earth, should at least aim for the 1.5 ºC. Therefore, the 126 Mt and 205 Mt budgets for Dutch aviation are considered to be fully in line with the Paris agreement,

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230219 - Carbon budget aviation – January 2024

whereas the other two budgets explore the upper boundary. — An economic approach for the decarbonisation leads to an increase of aviation compared to other sectors due to the fact that aviation is a ‘costly to abate’ sector. — However, aviation is not a basic need and for many people a luxury product. One might also argue that aviation has to follow the same or even a more restrictive path than other sectors. If a family has not enough money they probably will skip the summer holiday before they stop drastically reduce eating or heating. — In the distribution of the aviation budget between the Netherlands and other countries, the historic high amount of emissions is used as a starting point for determining the Dutch budget. This implies that the Dutch budgets have to be interpreted as maximum budgets. An approach that would require more efforts by developed countries than by developing countries would lead to lower budgets.

Budget per average person Since a budget of 205 Mt or any other of these budgets is very abstract, we have made the effort to translate it to a budget for the average Dutch person and compare it to the average global citizen. This is a theoretical exercise and we are aware of the fact that different ethical considerations would lead to very different results.

To derive the remaining budgets for Dutch passengers, we first subtract the realized emission between 2020 and 2023 from the initial budget. Despite the significantly reduced aviation activities as a consequence of the COVID19 pandemic, 34 Mt or 17% of the budget has already been used. The remaining budget of 171 Mt is associated with 19% to freight and 81% to passenger leading to a remaining budget of 138 Mt (ICCT, 2019). This budget is further distributed between transfer passengers (38%), visitors of the Netherlands (24%) and Dutch inhabitants (38%) according to the distribution of CO2 emissions in 2019. The remaining budget for Dutch passengers is 52.3 Mt, but includes only the departing flights. Therefore, the budget is multiplied by a factor two (104,6 Mt), since these passengers are counted as visitors in the budgets of other countries according to this method. Dividing this budget by 17.5 million inhabitants leads to a personal budget of 6 ton CO2 for the average Dutch person. As a comparison, we have estimated the carbon budget for the average global citizen. When subtracting the global aviation emission between 2020 and 2023 and 19% for air freight, the remaining global budget for passengers is 13 Gt. ________________________________ 19

CO2 emissions per flight are estimated with the ICAO carbon emissions calculator https://www.icao.int/environmental-protection/Carbonoffset/Pages/default.aspx

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230219 - Carbon budget aviation – January 2024

Dividing by 8 trillion people leads to a personal budget of 1.6 ton. The budget of the average Dutch person is 3.7 times larger than the budget of the average citizen according to this theoretical allocation method. With the current aircrafts and fuels, the budget of 6 ton CO2 corresponds to: — 25.5 flights19 to Barcelona (economy class); or — 9.5 flights to New York (economy class); or — 7.3 flights to Tokyo (economy class); or — 2.4–3.6 flights to Tokyo depending on the chair configuration (business class). These numbers increase, with the expected efficiency improvements and SAF blending. If we assume ambitious climate policies that lead to zero-emission aviation in 2050 and a linear path for the years in between, the average Dutch person could fly twice a year to Barcelona or almost once a year to New York (and back) based on this budget.

4.6

Hard-to-abate curves vs. immediate reduction

In aviation decarbonization roadmaps (see Figure 9 for an example), net-zero in a specific year is usually reached by a path that has lower reduction targets in the first years and accelerates after 2030. This accelerating speed curves are motivated by the time needed to ‘scale up’ new technologies.

This is in line with the shape of the SAF blending targets in the ReFuelEU Aviation proposal (6% in 2030, 20% in 2035, 34% in 2040, 42% in 2045 and 70% in 2050). Considering the remaining available budgets and the speed at which they are running out, such a pathway is no longer feasible for three of the four budgets without immediate action. Figure 10 – Potential reduction paths for a remaining carbon budget of 205 Mt

Figure 9 – Annual global aviation CO2 emissions (well-to-wing) until 2050 for different

14.0

aviation forecasts

CO2 emissions (Mt)

12.0 10.0 8.0 6.0 4.0 2.0 0.0

2020

2025

2030

Accelerating speed

Source: (ICCT, 2022).

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230219 - Carbon budget aviation – January 2024

2035

2040

2045

Immediate action

2050

2055

Linear reduction

2060

In Figure 10 three indicative reduction paths for the 205 Mt budget are shown. Since the area under all curves is identical the shape determines the year in which zero has to be reached. The three examples are: — Linear reduction path: This approach reaches zero emissions in 2052. — Accelerating speed: Moderate reduction in the first years requires zero emissions much earlier than 2050. — Immediate action: Fast emission reduction before 2030 allows that zero emissions could be reached after 2050, for instance by increasing SAF blending from 70 to 100% between 2050 and 2060.