Bijlage 3 CE_Delft_230219_Carbon_budget_aviation_Def.pdf

highly uncertain. A risk is that additional blending in Europe cannibalizes the world market. However, this would probably be necessary to reach zero before 2050. The potential energy demand for all these technologies puts additional pressure on the decarbonization of other sectors and regions worldwide (see also Text box 13). Text box 13 – Consequences for renewable energy sources in NL NLR (2023) has estimated the total primary energy required for aviation in the Netherlands in 2050 for each of the four scenarios considered. In the least ambitious scenario (66% likelihood of 1.7 ºC, 3.9%) this primary energy use is about 100 PJ higher

Both the linear and the accelerating speed variants depend on breakthroughs in aircraft technology, carbon removal or SAF production way before 2050. Whether electric/hydrogen aircrafts or large scale carbon capture and storage (in addition to direct air capture for the production of synthetic fuels) will be available in time is very uncertain. The aircraft that are currently being developed will dominate the fleets in 2050, and these still rely on fossil fuel or SAF.

than the most ambitious scenario (50% likelihood of 1.5 ºC warming, 2.4% aviation share), as in the least ambitious scenario the number of remaining flights is higher hence more SAF and carbon removal is needed. As we assume climate neutrality in 2050, all energy needs to be generated from renewable sources. To put this 100 PJ in perspective, about 550 wind turbines of 10 MW each are needed to generate this amount of energy in the form of electricity on an annual basis20. This is almost one-third of all wind turbines that are projected to have been constructed in the Dutch part of the North Sea around 2030 (Rijksoverheid, n.d.)21. To be sure, these 550 wind turbines would only produce the electricity corresponding to the additional renewable energy required to make the least

SAF production capacities will probably be scaled up significantly in the next decades. Whether sufficient clean energy and biomass is available for the global demand is

ambitious scenario for aviation possible, compared to the most ambitious scenario.

________________________________ 20

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Assuming 5,000 full-load hours per wind turbine.

230219 - Carbon budget aviation – January 2024

21

The number of wind turbines in the North Sea in 2050 is still very uncertain.

Apart from the renewable energy needs associated with the production of SAF, bio-based SAF also requires sustainable biomass, which is then not available anymore for other economic sectors. In the least ambitious scenario, about 0.9 Mt of SAF would be needed additionally in 2050 (NLR, 2023), which corresponds to about 1.6 Mt or 60 PJ of biomass22.

4.7

Reduction paths and 2030 targets

According to CE Delft and Royal HaskoningDHV (2020) the availability of sustainable biomass for the Netherlands in 2050 is estimated at 372-454 PJ annually. This would mean the Dutch aviation sector would lay hold of 13-16% of the available sustainable biomass only for the difference between the most and least ambitious scenarios.

For the highest budget (287 Mt) different reduction paths are possible, although those imply moderate emission reduction until 2030. For the other three budgets (205 Mt, 176 Mt and 126 Mt) immediate action is required to prevent dependency on technological breakthroughs, and to limit the risk of overshooting the carbon budget. Otherwise, even more drastic measures are necessary in the future to stay within the remaining carbon budgets.

________________________________ 22

Using the conversion factor of 0.04 EJ/Mt from NLR, & SEO. (2021). Destination 2050: A Route to Net-Zero European Aviation.

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During the period 2020 to 2024, approximately 46 Mt of the remaining budgets will be used despite the reduced activities caused by the COVID19 pandemic. With the current level of emissions the 205 Mt budget is exhausted in 2038 (13.6 years), the 126 Mt budget in less than 7 years. We have defined logical stepwise-linear reduction paths for Dutch aviation that fit to the four remaining carbon budgets calculated in Section 4.5. The immediate action is assumed to start in 2025. Later action would require more drastic measures.

Table 7 - Reduction targets for 2030 and 2050 compared to 2019 emissions for the four

Figure 11 - Reduction paths for the four remaining carbon budgets

remaining carbon budgets 14.0

2030

2050

287 Mt budget (1.7 °C, 3.9%)

-5%

-63%

10.0

205 Mt budget (1.5 °C, 3.9%)

-30%

-81%

8.0

176 Mt budget (1.7 °C, 2.4%)

-47%

-84%

126 Mt budget (1.5 °C, 2.4%)

-77%

-90%

CO2 emissions (Mt)

12.0

6.0 4.0 2.0 0.0 2020

2025

287 Mt budget -5%

2030

2035

2040

205 Mt budget - 30%

2045

2050

2055

176 Mt budget - 47%

2060

2065

2070

126 Mt budget -77%

The 287 Mt can be reached by setting a zero emission target in 2063 and defining a linear path between the current 2030 target (equal to 2005 level) and 2063. The other budgets require immediate action. Our ‘immediate reduction’ pathways have a linear reduction between 2025 and goal in 2030 to prevent very strong declines from one year to another. In addition, they contain SAF blending according to RefuelEU and full carbon removals for any remaining emissions after 2050 in line with Destination2050 (see Figure 11 and Figure 12).

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The targets for 2030 and 2050 are summarized in Table 7. To align with a 1.5 ºC pathway, at least 30% CO2 reduction is needed in 2030, based on a 3.9% share of aviation in total emissions. If aviation maintains its current share, CO2 emissions must be around 77% lower in 2030. For three of the four scenarios the 2030 reduction targets are significantly more ambitious than the goal of -9% of the Duurzame Luchtvaarttafel. For the 287 Mt budget the extent to which this budget is Paris-aligned is debatable. Worthwhile to mention is that the -5% for 2030 in the existing commitment of the industry itself (Destination2050 and LTAG) cannot be considered anymore as to be aligned with 1.5 ºC. In the 287 Mt budget remaining emission after 2050 can be reduced to zero by increasing SAF blending or by carbon removal. For the other three carbon budgets carbon removal is required from 2050 onwards. In the 205 Mt budget the assumed demand for carbon removal is higher (19% of 2019 emissions) than in the 126 Mt budget (10%). This implies that

the clean energy demand and the dependence of large scale carbon removal after 2050 is much higher in the 205 Mt variant. Figure 12 – Overview of emission in time periods. The CO2 ceiling shows the potential budget that would fit in the proposed CO2 ceiling. The percentages illustrate the reduction targets for 2030 400 350

CO2 budget (Mt)

300

1.7° | 3.9% ​

250 ​

1.5° | 3.9%

200 1.7° | 2.4% ​ 150

For the 205 Mt budget a sensitivity analysis is performed for situations with and without carbon removal after 2050. The defined scenarios are: — A scenario with moderate carbon removal from 2050 onwards (8% compared to the ‘hypothetical no-action growth’ scenario) as proposed in Destination 2050. — A scenario without carbon removal, which assumes an increase in SAF blending from 70% in 2050 to 100% in 2060. Th scenario with carbon removal requires a CO2 reduction of 30% in 2030, without carbon removal this target needs to be increased to 37%. In 2050, emissions have to be reduced by 81% compared to 2019 in both scenarios. See Figure 13 for a comparison of the reduction paths.

​ 1.5° | 2.4% ​

100 50

0 CO2 ceiling

287 Mt budget -5% 205 Mt budget 30% 2020-2023

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Reduction paths with and without carbon removal

2024-2030

176 Mt budget 47%

2031-2050

230219 - Carbon budget aviation – January 2024

2051-2070

126 Mt budget 77%

We conclude that in 2030 a reduction between 30 and 37% compared to 2019 has to be achieved, which is significantly more than the goal of -9% of the Duurzame Luchtvaarttafel.

Figure 13 - Scenarios for 205 Mt budgets with and without carbon removal after 2030 and its implications on the reduction targets for 2030 14.0

CO2 emissions (Mt)

12.0 10.0 8.0 6.0 4.0

2.0 0.0 2020

2025

2030

2035

2040

2045

2050

Carbon removal after 2050

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230219 - Carbon budget aviation – January 2024

2055

2060

2065

No carbon removal

2070

4.8

Comparison of budgets to current and planned policies

The Dutch emission reduction goals for aviation are defined in the Civil Aviation Policy Memorandum ‘Luchtvaartnota’ and acknowledged in the coalition agreement of the current government. Currently, legislation is in preparation to enforce these goals by introducing a national CO2 ceiling for all commercial flights departing from Dutch airports. The goals are: — limit CO₂ emissions to 2005-levels by 2030; — reduce them by 50% (relative to 2005) by 2050; — reach zero by 2070. In the CO2 ceiling, SAF is counted as zero emissions, which implies that the actual climate impact is higher than the budget of the CO2 ceiling. Currently, biofuels have lifecycle savings around 65%. In the future, these percentage will increase and synthetic fuels might even become 100% carbon neutral when produced with 100% renewable energy. In the meanwhile this choice leads to a higher remaining budget than a choice in which SAF emissions would be taken into account.

Next to this policy, the current government has announced the reduction of the annual capacity at Schiphol Airport from 500,000 to 440,00023 flights per year in the period 2025-2029. Afterwards, the sector is given the perspective to grow under not yet defined conditions. We compare the different options with the four carbon budgets that we have derived from the global IPCC budgets and investigate whether the policies are sufficient to comply. We will also discuss how policies could be adjusted to cope with smaller budgets for Dutch aviation. Figure 14 compares current and planned policies with the four found Dutch CO2 budgets, Figure 15 visualises their emissions over time.

________________________________ 23

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In a revised plan from 1 September 2023 this number has been adjusted to 452,000 flights.

230219 - Carbon budget aviation – January 2024

Figure 14 – Cumulative CO2 emissions of policies compared to the Dutch CO2 budgets

The ‘500k constant no SAF’ scenario assumes the current capacity restrictions at Schiphol of 500,000 flights, no SAF uptake, medium socio-economic growth (average of WLO Low and High) and associated efficiency improvements.

Figure 15 – CO2 emissions of various scenarios and policies

It illustrates a scenario in which no additional sustainability measures are taken, and decarbonisation is only driven by efficiency improvements of aircraft. This scenario would lead to cumulative emissions of 586 Mt and severely overshoot all of the 1.5 ºC and 1.7 ºC budgets. It shows that using SAFs instead of fossil fuels is a basic requirement for the decarbonization of aviation.

All visualised scenarios (except the CO2 ceiling) are AEOLUS model runs. WLO Low and High results are averaged. The CO2 emissions from SAF are corrected by using the CORSIA guidelines.

The ‘500k constant’ scenario has a capacity limit of 500,000 flights for Schiphol and assumes medium socio-economic growth. The difference is that the announced SAF blending obligation of the RefuelEU Aviation policy is applied. The impact of SAF blending nearly halves the cumulative emissions to 306 Mt. Note, that we apply a life-cycle approach

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here in which SAF is not counted as zero emissions but emission savings compared to fossil kerosene are applied24. These cumulative emissions are still higher than all of the 1,5 ºC and 1,7 ºC budgets, but get closer to the ‘1.7 ºC| 3.9%’ budget of 287 Mt. This ‘500k constant’ scenario can be interpreted as a ‘baseline scenario’ without national policies. In Figure 14 and Figure 15 two proposed national policies are investigated: the announced national CO2 ceiling and a capacity reduction at Schiphol to 440.000 movements per year (440k variant). The cumulative CO2 emissions under the CO2 ceiling would overshoot all of the 1.5° and 1.7° budgets with 327 Mt. It is even higher than the ‘500k constant’ baseline scenario. The main reason for this is that the CO2 ceiling assumes linear decreasing emissions until decarbonisation in 2070 (see Figure 14). Our baseline scenario shows an acceleration in decarbonisation after 2045, in line with the RefuelEU Aviation blending proposal, leaving quite some ‘unused’ CO2 budget between 2050 and 2070.

________________________________ 24

For biofuels the assumed emission savings are 65% until 2030 and increase linearly to 95% in 2050. For RFNBOs/synthetic fuels the savings are 85% in 2030 and 100% in 2050.

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An important sidenote is that the CO2 ceiling as it is currently proposed by the Ministry of Infrastructure and Water Management does only include emissions from kerosene, SAFs are counted as zero CO2 emissions. In fact, SAFs do still have remaining CO2 emissions. For example current biofuels used for aviation have 65% life-cycle savings (EC, 2021), which means that 35% of the CO2 is still emitted. When taking this into account, using the blending percentages from RefuelEU Aviation, the cumulative emissions until 2050 are increased by 13 Mt visualised with the errorbar. The ‘440k variant’ represents a 440,000 flights restriction at Schiphol starting in 2024, medium socio-economic growth and SAF blending according to RefuelEU Aviation. We find that this policy would reduce the cumulative CO2 emissions of Dutch aviation to 280 Mt. This is in line with the ‘1.7º | 3.9%’ budget. However, the emissions are still much higher than the other carbon budgets.

4.9

Considerations on global scale of aviation

Measures for sustainable aviation should in principle be introduced on the largest possible geographic scale due to the international character of aviation. If the number of (intercontinental) flights from the Netherlands is reduced, a large fraction of passengers and cargo operators will switch to other airports. Another part will fly less as a consequence of a decline in connectivity and higher ticket prices. Part of the emission reduction at Dutch airports will be compensated by more emissions at other airports if they have less ambitious reduction targets. However, in all detailed model calculations overall reduction was found when the capacity is decreased at Schiphol (CE Delft et al., Ongoing) (CE Delft, 2022). If the ambition to reduce CO2 is much higher in the Netherlands than in neighbouring or competing countries worldwide, this may lead to competitive disadvantages on the short term. Not taking this action, will have tremendous consequences on the long term. The aviation industry worldwide has to answer the question how they prevent a substantial overshoot of the remaining carbon budget. Action is necessary in all parts of the world.

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This includes the development of new technology, fast upscaling of sustainable fuels but also ambitious demand management. The instruments that are currently in place are not sufficient. They need to be updated or replaced as soon as possible.

5 Impacts on the number of flights at Schiphol in 2030

The number of flights that fits into this budget depends on the development of the key variables: — aircraft and operational efficiency improvements; — SAF blending (6% in RefuelEU Aviation); — aircraft size; — flight distance.

In the previous chapter different remaining CO2 budgets for Dutch aviation have been estimated. For logical reduction paths for each of these budgets, reduction targets for 2030 have been calculated. The resulting annual CO2 budgets for Schiphol in 2030 are summarized in Table 8. In the analysis the share of Schiphol from the total Dutch budget is set to 95%, which is the current share. Table 8 – Remaining annual carbon budgets for Schiphol in 2030 2030 budget (Mt CO2/yr)

Carbon removal after 2050

287 Mt budget (1.7 °C, 3.9%)

10.4

No

205 Mt budget (1.5 °C, 3.9%)

7.6

Yes

6.9

No

176 Mt budget (1.7 °C, 2.4%)

5.8

Yes

126 Mt budget (1.5 °C, 2.4%)

2.5

Yes

This chapter investigates the impacts of the 2030 target on the number of flights for the ‘1.5 °C, 3.9%’ variant without carbon removal. The annual budget in 2030 is 6.9 Mt CO2.

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The fuel efficiency of new aircraft increases due to more efficient engines, improved aircraft designs and different material use. Replacement of old aircraft with new models leads to lower fuel use per revenue passenger kilometre. The average aircraft is operable for about 30 years. This implies that aircraft that will be replaced in the upcoming years will still be in operation in 2050, when the aviation sector wants to be net-zero. Aircraft that are currently in planning at the large manufacturers still make use of the current technology and will require fossil kerosine or SAF for the operations. Hence, the major part of the aircraft in operation will still use the current technology in 2050 with improved efficiency. 1 to 1.5% improvements per year are realistic (ICCT, 2022) (NLR & SEO, 2021). In addition, operational improvements might lead to additional fuel savings of a few percent, Until 2030, efficiency improvements between 10 and 15% are realistic.

SAF blending will increase significantly in the next decades. ReFuelEU includes a blending obligation of 70% SAF in 2050 for departures from European airports. Due to more efficient production chains, upscale of clean energy production and the production of synthetic fuels at large scale, the life-cycle emissions for SAF are expected to decline significantly. However, in 2030 SAF blending will still be in the fledgling stages, with a blending obligation of 6% in ReFuelEU Aviation25. In recent decades aviation emissions have been growing due to an increase in the number of aircraft movements but also due to larger aircraft types (that require more fuel than smaller ones) and an increase in flight distance. It is important to realize that a capacity limit on the number of aircraft limit stimulates the use of larger aircraft types. For our estimation of the number of aircraft movements that fit into the budget, we take the expected efficiency improvement until 2030 and blending into account. We show the results for different shares of European and intercontinental flights as a proxy for the change in average flight distance and for different developments in aircraft size.

________________________________ 25

The Dutch ministry of transport has formulated the ambition to introduce a national blending obligation of 14% in 2030. However, this is prohibited by ReFuelEU Aviation.

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We derive potential numbers of aircraft movements that fit into this budget in 2030 based on the results of the Dutch WLO aviation scenarios. The average forecast of the WLO Low and High scenario’s for 2030 has the following characteristics (compared to 2019): — 500,000 aircraft movements (+0%): • 375,000 European flights (-6%); • 125,000 intercontinental flights (+25%). — 96.6 million passengers (+35%); — 1.05% annual fuel efficiency improvement (-11%); — 6% SAF blending (+6%); — 11.4 Mt CO2 (-1%). In the WLO the efficiency improvements, SAF blending and constant capacity restriction do not lead to a CO2 emission reduction until 2030 even with a constant number of aircraft movements, since they are compensated by larger aircraft (more passengers) and longer flight distances (more ICA). In the WLO scenarios an increase in the number of passengers per flight of 2.7% per year is modelled. This is slightly higher than the historic growths of 2.3% per year, in the 25 years before the Covid pandemic. The reason is that the ceiling on the number of aircraft movements at Schiphol is an incentive to operate larger aircraft types within a limit number of slots.

Figure 16 - Potential number of flights in 2030 at Schiphol in line with the 205 Mt budget

aircraft size (and 10% intercontinental flights) the limit would be 340,000 flights only. However, with a reduction of the share of intercontinental flights to 11% and the current aircraft size up to 557,000 flights could fit into the budget. This estimation shows that the maximum number of flights that fits into the budget strongly depends on the share of intercontinental flights and the assumed development in aircraft sizes. With additional SAF blending for all departing flights from Dutch airports the emissions per flight can be reduced making more flights possible within the same budget. If the blending percentage would be 14% instead of 6% in 2030 about 6% additional flights are possible assuming 70% LCAemission reduction of SAF compared to fossil fuels.

Figure 16 shows the possible number of flights in 2030 for different shares of intercontinental flights and different developments in aircraft size. For the average aircraft size three options are considered: — the current size (no growth); — the assumed growth in the WLO scenario’s (high growth); — and the average between the two (low growth). With the current aircraft sizes and distribution between European (80%) and intercontinental flights (20%) this would limit operations to 419,000 flights. With an increase in

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For the largest budget of 10.4 Mt (‘1.7°C, 3.9%-variant’) the announced 452,000 aircraft movements could be reached with a decrease in the number of intercontinental flights. For the two smaller budgets of 5.8 Mt (‘1.7 °C, 2.4%-variant’) and especially for the budget of 2.5 Mt (‘1.5 °C, 2.4%-variant’) the total number of flights and especially the number of intercontinental flights has to be reduced very significantly. A quantitative estimation is not included in this report.

6 References Bauen, A., Bitossi, N., German, L., Harris, A., & Leow, K. (2020). Sustainable Aviation Fuels : Status, challenges and prospects of drop-in liquid fuels, hydrogen and electrification in aviation. Johnson Matthey Technology Review, 64(3), 263-278. Becken, S., Mackey, B., & Lee, D. S. (2023). Implications of preferential access to land and clean energy for Sustainable Aviation Fuels. Science of the Total Environment(886). CE Delft. (2018). Taxing Aviation Fuels in the EU. CE Delft. (2021). Effects of the Fit for 55 Package on the Dutch Aviation Sector. CE Delft. (2022). Updated impacts of a CO2-ceiling for Dutch aviation. CE Delft. (2023). Koolstofverwijdering voor klimaatbeleid: Analyse van behoefte, aanbod en beleid voor negatieve emissies in Nederland. CE Delft, Manchester Metropolitan University, & Opportunity Green. (2022). Potential for reducing aviation non-CO2 emissions through cleaner jet fuel. CE Delft, & Resource Analysis. (2000). National allocation of international aviation and marine CO2 emissions. CE Delft, & Royal HaskoningDHV. (2020). Bio-Scope : Toepassingen en beschikbaarheid van duurzame biomassa. Climate Action Tracker. (n.d.). International Aviation.

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CO2emissiefactoren.nl. (2023, 20-01-2023). Lijst emissiefactoren. CO2 emissiefactoren,. http://www.co2emissiefactoren.nl/lijstemissiefactoren/ Council of the EU. (2022). ETS aviation: Council and Parliament strike provisional deal to reduce flight emissions. Council of the European Union. Council of the EU. (2023a). Council and Parliament agree to decarbonise the aviation sector. Council of the European Union. Council of the EU. (2023b). Council and Parliament reach provisional deal on renewable energy directive. Council of the European Union. Council of the EU. (2023c). Fit for 55. Crippa, M., Guizzardi, D., Solazzo, E., Muntean, M., Schaaf, E., F., P., Monforti-Ferrario, F., Banja, M., Olivier, J. G. J., Quadrelli, R., Grassi, G., Rossi, S., Vignati, E., Oom, D., Branco, A., & San-Miquel, J. (2022). CO2 emissions of all world countries. Crippa, M., Guizzardi, D., Solazzo, E., Muntean, M., Schaaf, E., Monforti-Ferrario, F., Banja, M., Olivier, J. G. J., Grassi, G., Rossi, S., & Vignati, E. (2021). GHG emissions of all world countries. Dosio, A., Mentaschi, L., Fischer, E. M., & Wyser, K. (2018). Extreme heat waves under 1,5 C and 2 C global warming. Environmental Research Letters, 13(054006). EASA, David S. Lee, Manchester Metroplitan University, & CE Delft. (2020). Updated analysis of the non-CO2 climate impacts of aviation and potential policy measures

pursuant to the EU Emissions Trading System Directive Article 30(4), Final report. EC. (2020). Update of the NDC of the European Union and its Member States . Submission by Germany and the European Commission on behalf of the European Union and its Member States. EC. (2021). Proposal for a Directive of the European Parliament and of the Council amending Directive (EU) 2018/2001 of the European Parliament and of the Council, Regulation (EU) 2018/1999 of the European Parliament and of the Council and Directive 98/70/EC of the European Parliament and of the Council as regards the promotion of energy from renewable sources, and repealing Council Directive (EU) 2015/652, COM/2021/557 final. European Commission (EC). EEA. (2023). EU Emissions Trading System (ETS) data viewer. European Environmental Agency (EEA). https://www.eea.europa.eu/data-andmaps/dashboards/emissions-trading-viewer-1 EP. (2021). Sustainable and smart mobility strategy Delivered at local level. European Union (EU). EP. (2022). The future of climate migration. European Parliament (EP). EP. (2023). Fit for 55: Parliament and Council reach deal on greener aviation fuels. European Parliament (EP). EU. (2018). Directive (EU) 2018/2001 of the European Parliament and of the Council of 11 December 2018 on the promotion of the use of energy from renewable

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sources (Text with EEA relevance.). Official Journal of the European Union, L 328(21.12.2018), 82-209. EU. (2021). Regulation (EU) 2021/1119 of the European Parliament and of the Council of 30 June 2021 establishing the framework for achieving climate neutrality and amending Regulations (EC) No 401/2009 and (EU) 2018/1999 (‘European Climate Law’). Official Journal of the European Union, L243(9.7.2021), 1-17. Forster, P. M., Smith, C. J., Walsh, T., & al., e. (2023). Indicators of Global Climate Change 2022: annual update of large-scale indicators of the state of the climate system and human influence. Earth System Science Data(15), 2295-2327. IATA. (2021). Net-Zero Carbon Emissions by 2050. IATA. (2023). CORSIA Fact sheet. IATA. (n.d.). Our Commitment to Fly Net Zero by 2050. ICAO. (2022). Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) - Frequently Asked Questions (FAQs). Environmental Protection. ICAO. ICAO. (n.d.-b). The history of ICAO and the Chicago Convention. ICCT. (2019). CO2 emissions from commercial aviation 2018. ICCT. (2020). CO2 emissions from commercial aviation. ICCT. (2022). Vision 2050 - Aligning aviation with the Paris Agreement. IEA. (2019). The Future of Hydrogen : Seizing today's opportunities.

IEA. (2021). Net Zero by 2050: A roadmap for the global energy sector. IEA. (2023a, 11 July 2023). Aviation. IEA. (2023b). CO2 emissions in 2022. IPCC. (2018). Special Report: Global Warming of 1.5C: Summary for Policymakers. IPCC. (2022). Summary for Policymakers: Climate Change 2022: Impacts, Adaptation and Vulnerability. IPCC. (2023). Climate Change 2023. AR6 Synthesis Report. ITF. (2023). The potential of E-fuels to Decarbonise Ships and Aircraft. Jensen, L. (2022). At a glance - Revision of the EU emissions trading system: Aviation. European Parliamentary Research Service (EPRS). Lee, D. S., Fahey, D. W., Skowron, A., Allen, M. R., Burkhardt, U., Chen, Q., Doherty, S. J., Freeman, S., Forster, P. M., Fuglestvedt, J., Gettelman, A., De León, R. R., Lim, L. L., Lund, M. T., Millar, R. J., Owen, B., Penner, J. E., Pitari, G., Prather, M. J., Wilcox, L. J. (2021). The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018. Atmospheric Environment, 244, 117834. Loupatty, A. (2023, 11 mei 2023). Brussel blokkeert Nederlandse duurzaamheidsdoelen luchtvaart. BNR. Minister van I&W. (2023a). Kamerbrief dd 17 maart 2023 over Principebesluit CO2-plafond luchtvaart. Minister van I&W. (2023b). Kamerbrief dd 30 maart 2023 betreft Beleidsaanpak niet-CO2-klimaateffecten luchtvaart.

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Ministerie van I&W. (2020). Verantwoord vliegen naar 2050 : Luchtvaartnota 2020-2050. NLR. (2023). CO2 and resulting flight restrictions for Amsterdam Airport Schiphol based on remaining IPCC CO2 budgets up to 2050. NLR, & SEO. (2021). Destination 2050: A Route to Net-Zero European Aviation. Rijksoverheid. (2021). Coalitieakkoord 2021-2025: Omzien naar elkaar, vooruitkijken naar de toekomst. VVD, D66, CDA en ChristenUnie. Rijksoverheid. (n.d.). Waar staan en komen de windparken op zee? Science Based Targets. (2021). Science-based target setting for the aviation sector. Science Based Targets. (n.d.). Lead the way to a low-carbon future. Science Based Target initiative (SBTi). SEO, CE Delft, & Significance. (2023). Schiphol: krimpen of verduurzamen? T&E. (2021). Don't sink Paris: Legal basis for inclusion of aviation and shipping emissions in Paris targets. T&E. (n.d.). Non-CO2 effects of aviation. Transport and Environment (T&E). Tanzer, S. E., & Ramirez, A. (2019). When are negative emissions negative emissions? Energy & Environmental Science, 12, 1210-1218. TU Delft. (2023). Flying-V. UCAR. (n.d.). Key Climate Tipping Points. University Corperation for Atmospheric Research (UCAR) Centre for Science Education.

UN. (1992, May 9). United Framework Convention on Climate Change. United Nations (UN). UN. (2015). Paris Agreement. UNFCCC. (1998). Kyoto Protocol to the United Nations Framework Convention on Climate Change. UNFCCC. (2019). Report of the Conference of the Parties serving as the meeting of the parties to the Paris Agreement on the third part of its first session, held in Katowice from 2 to 15 december 2018 - Addendum Part II. UNFCCC. (n.d.). Emissions from fuels used for international aviation and maritime transport. UNFCCC. West, T. A. P., Wunder, S., Sills, E. O., Börner, J., Rifrai, S. W., Frey, G. P., & Kontoleon, A. (2023). Action needed to make carbon offsets from forest conservation work for climate change mitigation. Science(381-6660), 873877. WMO. (2023). July 2023 is set to be the hottest month on record. World Bank. (2021). Climate change could force 2016 million people to migrate within their own countries by 2050. World Bank.

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Annexes

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A Non-CO2 effects Next to the emissions of greenhouse gases (GHGs), aviation impacts climate through indirect effects of emissions and changes to the atmosphere. The best estimate of the combined worldwide non-CO2 climate impacts of aviation from 1940 to 2018 in terms of the current effective radiative forcing are twice as large as the CO2 impacts, although there is still a considerable scientific uncertainty about their quantification. Despite their importance, there has been very limited policy action to address the non-CO2 impact. 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 there they do not contribute as greenhouse gases. In the atmosphere they have chemical and physical effects which contribute to global warming. 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, as CO2 remains in the atmosphere for a

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relatively long period of time, but the non-CO2 emissions are short-lived as they break down quicker through chemical reactions. The different timescales of the CO2 and non-CO2 effects make it difficult to compare the effects to global warming. An attempt to make them comparable is to define CO2 equivalents (CO2e). They can be estimated for different metrics and time horizons. We have developed a simplified conceptual model to illustrate the effect of the different time horizons, since this is essential to answer the question how the non-CO2 climate impact should be considered in the IPCC GHG-budgets. The lifetimes of the most important climate forcers are: — CO2: centuries to millenniums; — water vapour: months; — higher ozone concentrations as a consequence of nitrogen oxides: weeks; — lower methane concentrations as a consequence of nitrogen oxides: 12 years. In the conceptual model the lifetime of CO2 is approximated with more than 100 years and for the non-CO2 effects one year is assumed. The development of aviation is described for a fictive period of 100 years, 50 years in the past and 50 years in the future. For the development in the past an annual growth rate for fuel of 5% is assumed. For the period

1971-2020 the warming effect of CO2 and non-CO2 emissions are calibrated26 to 1/3 and 2/3 according to Lee et al. (2021). Table 9 illustrates that the share depends on the time period considered, due to the difference between cumulative CO2 and short-lived non-CO2. Just considering a single year (2020) leads to a lower non-CO2 share than when evaluating the entire period. Table 9 - Share of the non-CO2 effects in effective radiative forcing (ERF) for different time periods in time according to the conceptual modelTable Period

Share of non-CO2

1971-2020

66.7%

1996-2020

64.5%

2011-2020

63.4%

2020

62.9%

In Figure 17, the historic development of the CO2 and non-CO2 impact is illustrated for flights until 2020. After 2020, the warming effect of the historic CO2 emissions persists and is equal to the overall effect, since non-CO2 has no effect in future years in the conceptual model. In reality, this is not completely true since some agents have a longer lifetime, but this is negligible when long-term effects are considered. ________________________________ 26

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The calibration factor between non-CO2 and CO2 used in this model is 32.5.

230219 - Carbon budget aviation – January 2024

Figure 17 - Results of the conceptual model for CO2, non-CO2 and total effect of aviation on global warming

Hypothetical future developments We now discus the effects of hypothetical future developments of aviation and its implications on the CO2 and non-CO2 climate impact.

Figure 18 – Forecast of the conceptual model in case efficiency gains are equal to demand growths and no SAF blending

Assuming that the growths of aviation would be equal to the efficiency improvements and no SAF would be blended in the future. This scenario would lead to a constant demand of kerosine. The consequences are shown in Figure 18. The non-CO2 effects are at a constant level and CO2 increases over time. Hence, the share of climate impact of non-CO2emissions decreases over time.

When SAF blending is assumed according to the ReFuel EU Aviation proposal (see Figure 19), the WTW CO2 emissions decrease significantly27. Here, zero emissions for SAF is assumed, which is not completely in line with the 95% emission reduction we assume in the main study for biofuels in 2050. It is likely that SAF will have lower non-CO2 emissions since it has less aromatics (CE Delft et al., 2022). ________________________________ 27

This is an optimistic scenario, in which the announced EU-blending obligations is applied to all flights globally.

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However, there is still a large uncertainty about the magnitude of the climate impact reduction, which will be realized. Here, we chose two variants, a reduction of the nonCO2 effects by 25% and by 75%. The latter is very optimistic, when considering the fuels only. We consider this is a combined effect of adjusted flight paths together with additional technical and operational measures. Figure 19 – Assumed SAF blending. The share of SAF until 2050 is taken from the ReFuelEU aviation proposal and between 2050 and 2060 a linear increase from 70 to 100% is assumed

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The results are shown in Figure 20 and Figure 21 for two scenario’s, namely one with no growth in aviation fuel demand and the other with a 5% increase per year, the latter is in line with the historic develop of the last decades. In both scenarios, the climate impact of the CO2 emissions increases until 2060. Afterwards, no additional CO2 is emitted due to the usage of 100% SAFs. In case, of a constant fuel demand the non-CO2 effects are a constant offset from 2060 onwards. In the case of growths, the share of SAFs on global warming increases after 2060. The impact strongly depends on the non-CO2 emission reduction factor.

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Figure 20 – Development of emissions in case efficiency gains are equal to demand growths. SAF blending increases as proposed in the ReFuelEU Aviation proposal and reaches 100% in 2060. For the reduction of the non-CO2 effects two scenarios are

Figure 21 - Development of emissions in case demand growths faster than efficiency improvements. SAF blending increases as proposed in the ReFuelEU Aviation proposal and reaches 100% in 2060. For the reduction of the non-CO2 effects two scenarios are

distinguished, 25 and 75% reduction compared to fossil kerosine

distinguished, 25 and 75% reduction compared to fossil kerosine

230219 - Carbon budget aviation – January 2024

Trade-off between CO2 and non-CO2 emissions Although, there is still a large scientific uncertainty on the non-CO2 effects of aviation, a very significant reduction is required to bring aviation in line with the Paris agreement. Trading between CO2 and non-CO2 emissions is difficult due to the large differences in the lifetimes in the atmosphere. A bit of extra CO2 emissions could lead to significance reductions of the non-CO2 effects, for instance by adjusted route choices per lower flight altitudes. However, the extra-CO2 would lead to global warming for a much longer time than the short-lived non-CO2 effects. This makes only sense in case the ratio between extra CO2 and non-CO2 reduction is very small. After 2060, the TTW CO2 emissions will be equal to zero. An adjusted route choice and hence extra fuel demand makes much more sense in this situation if it reduces the non-CO2 effects significantly. We assume for this study that effective policies will be developed to reduce the non-CO2 emission of aviation in the next decades. Adjusted route choices and a slight increase in sustainable fuel demand should be considered as realistic options. This should lead to a significant reduction of non-CO2 emissions. As a consequence, the non-CO2 effects do not have to be subtracted from the IPCC carbon budgets.

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We want to stress that the 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. Hence, it is very important to develop efficient non-CO2 policies and to reduce them as soon and as fast as possible.

B Scenario assumptions

Table 11 - Life-cycle CO2 savings for the average SAFs

All scenarios (except the CO2 ceiling) used in Section 4.6 are AEOLUS model runs. For the calculations in this report, the results of the two WLO scenarios (Low and High) are averaged to keep the analysis simple. The SAF assumptions are based on the RefuelEU Aviation blending obligations, and are stated in Table 10. Table 10 – RefuelEU Aviation blending obligation Fuel type

2019

2030

2040

2050

Fossil kerosene

100%

94%

66%

30%

Biofuels

0%

5%

15%

35%

Synthetic fuels

0%

1%

19%

35%

Since this study focusses on an aviation in-sector CO2 budget, the emission scope here is TTW. For SAF we follow the CORSIA guidelines for TTW emissions (Annex 16, Volume IV, Section 3.3). For kerosine a TTW emission factor of 3.11 kgCO2/kg fuel is used. To calculate the TTW emissions of SAFs, the emission factor of kerosine is multiplied by the life-cycle CO2 savings listed in Table 11.

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Fuel type

2019

2030

2040

2050

Biofuels

65%

65%

75%

95%

Synthetic fuels

85%

85%

90%

100%

Source: (NLR & SEO, 2021).

For the period after 2050, we assume that the blending obligation of RefuelEU Aviation will reach 100% SAF in 2060, with an equal mixture of biofuels and synthetic fuels. The life-cycle CO2 savings are assumed to be constant after 2050 in line with Table 11.

Colophon Delft, CE Delft, January 2024 This publication is prepared by: Stefan Grebe, Jasper Faber, Daan Juijn, Christiaan Meijer, Maarten de Vries, Merit Heijink, Frans Rooijers The results of this report have been discussed with various experts from Netherlands Aerospace Centre NLR, in particular to define the input assumptions and methodology. The authors are grateful for their useful suggestions and additions. Ownership and responsibility of the analysis presented lies with CE Delft. Publication code: 23.230219.146 Client: Royal Schiphol Group CE publications are available from www.cedelft.eu © copyright, CE Delft, Delft

CE Delft Committed to the Environment Through its independent research and consultancy work CE Delft is helping build a sustainable world. In the fields of energy, transport and resources our expertise is leading-edge. With our wealth of know-how on technologies, policies and economic issues we support government agencies, NGOs and industries in pursuit of structural change. For over 40 years now, the skills and enthusiasm of CE Delft’s staff have been devoted to achieving this mission.

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