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1、www.theicct.org communicationstheicct.orgtheicct.org WORKING PAPERJULY 2024Lifetime emissions from aircraft under a net-zero carbon budgetSupraja N.Kumar and Dan RutherfordSUMMARYThe commercial aviation sector is projected to grow rapidly in the coming decades,with an increase in traffic leading to

2、the doubling of the current fleet size and usage of aircraft.Nonetheless,in 2022,airlines and aircraft manufacturers committed to an international goal of achieving net-zero carbon dioxide(CO2)emissions by 2050.This goal was codified by the International Civil Aviation Organization(ICAO)at its 41st

3、Assembly.This study assesses whether current manufacturer delivery projections are consistent with this net-zero target.A net-zero carbon budget of 18.4 billion tonnes was defined for the sector,calculated as an average from four industry decarbonization roadmaps.In this paper,we model lifetime CO2

4、emissions from the 2023 global fleet and new aircraft deliveries through 2042 under three decarbonization scenarios,a business-as-usual(Baseline)scenario and scenarios that include the aggressive implementation of two key mitigation measuressustainable aviation fuels(SAFs;Optimistic SAF)and the use

5、of SAFs and fuel efficiency improvements(Optimistic SAF+Fuel Efficiency).We also consider a sensitivity analysis of more(1.5 C)and less ambitious(2 C)climate targets to contextualize the net-zero budget in terms of warming impact.We find that the 2023 in-service fleet is projected to emit about 9 bi

6、llion tonnes of CO2 before being retired,or almost half of a net-zero carbon budget.Lifetime emissions from new aircraft delivered from 2024 to 2042 are projected to exhaust the balance of a net-zero carbon budget between 2032(Baseline)and 2037(Optimistic SAF+Fuel Efficiency).This indicates that for

7、 airlines to achieve their climate goals,all new aircraft delivered by the mid-2030s will need to emit zero net CO2 emissions throughout their operational lifetimes.We also estimate there will be a market for at least 10,000 new aircraft powered by hydrogen,electricity,or 100%SAF through 2042.2024 I

8、NTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION(ID 188)Acknowledgements:The authors thank Sola Zheng,Nik Pavlenko,Jo Dardenne,and Michael Halaby for their reviews of this study,and Michael Doerrer for editing.This work was completed with the generous support of the Crux Alliance.2ICCT WORKING PAPER|LIF

9、ETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETBACKGROUNDAs commercial aviation confronts the challenge of balancing sectoral growth while progressing toward the International Civil Aviation Organizations(ICAO)2050 net-zero CO2 target,measures such as sustainable aviation fuels(SAFs),ai

10、rcraft efficiency improvements,and zero-emission planes(ZEPs)will be necessary to rapidly reduce emissions(Graver et al.,2022).According to the consensus of net-zero roadmaps(International Air Transport Association,2024a),SAFs are expected to provide more than half(53%)of all CO2 mitigation under a

11、net-zero pathway,followed by fuel efficiency at about 30%.Expectations of mitigation from ZEPs powered by hydrogen and electricity vary;in Graver et al.(2022),hydrogen-powered aircraft are responsible for 21%of total aviation energy use in 2050 but only about 5%of cumulative CO2 mitigation due to th

12、e gradual introduction of new aircraft types into the global fleet.To date,in order to address the climate crisis,manufacturers have been bullish on SAFs(Boeing,2023c;Airbus,2024),but have avoided concrete commitments to developing new,significantly more efficient aircraft types or ZEPs.While manufa

13、cturers tout the lower fuel burn of new aircraft,which is typically 15%lower than the generation they replace,the steady growth of the global fleet and its emissions indicates that many new aircraft support new traffic,instead of replacing older aircraft(Graver&Rutherford,2021).1 Central to all of t

14、hese measures are the aircraft themselves,with the cycle of production,deliveries,usage,and retirement dictating much of the industrys trajectory toward net-zero emissions.Each year,aircraft manufacturers release sustainability reports disclosing the emissions associated with their operations.Emissi

15、ons associated with the complete life cycle of delivered aircraft are captured within Scope 1,2,and 3 emissions disclosure by manufacturers.Scope 1 emissions are direct emissions from controlled or owned sources,such as manufacturing plants(U.S.Environmental Protection Agency,2020a).Scope 2 emission

16、s are indirect emissions released from the production of purchased electricity or power used for their operations(U.S.Environmental Protection Agency,2020b).Scope 3 emissions,or“value-chain emissions,”are those released during the lifetime of a products use by its customers.In March 2024,the U.S.Sec

17、urities and Exchange Commission finalized its ruling on corporate emissions disclosure.This ruling requires larger corporations to disclose Scope 1 and Scope 2 emissions,but Scope 3 emissions are not required to be reported at this time(U.S.Securities and Exchange Commission,2024).Meanwhile,the Euro

18、pean Union(EU)has released new rules,called the Corporate Sustainability Reporting Directive,requiring listed EU corporations,as well as foreign entities generating a large amount of revenue in the EU,to report Scope 1,2,and 3 emissions across their entire supply chain(Directive 2022/24/64).The stat

19、e of California recently introduced Scope 3 emissions disclosure requirements like those in the EU(Climate Corporate Data Accountability Act,2023).Scope 3 emissions account for more than 90%of an aircrafts lifetime emissions(Airbus,2022).Corporate reporting on these emissions allows companies and th

20、eir investors to measure progress toward climate goals,identify potential risks,and build climate resilience.Timely action to reduce Scope 3 emissions from aircraft is key to achieving the climate goals set by ICAO and various decarbonization pathways.1 For example,Graver and Rutherford(2021)found t

21、hat low-cost carriers,which purchase large numbers of new aircraft,were responsible for almost 90%of aviation CO2 growth in the United States from 2005 to 2019.Emissions growth from low-cost carriers exceeded that of network carriers because traffic,as measured in revenue passenger kilometers,increa

22、sed much faster(+119%)than fuel efficiency improved(+34%)compared to legacy carriers(+22%and+20%,respectively).This phenomenon,known as Jevons Paradox,refers to the scenario where efficiency gains lead to increases,not decreases,in resource use due to falling costs.3ICCT WORKING PAPER|LIFETIME EMISS

23、IONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETThe EU has adopted a classification framework(EU Taxonomy)to define whether economic activities are environmentally sustainable and guide investments in clean technology.In 2023,criteria for“green investments”in aircraft manufacturing,aircraft leasing

24、,and commercial passenger air transport were added.For a delivered aircraft to be considereda taxonomy-compliant investment,it must meet fuel efficiency improvement thresholds that are based on ICAOs CO2 standardand be shown not to increase the global fleet size.Starting in 2028,new aircraft must be

25、 compatible with 100%SAF use in order to be compliant with the taxonomy requirements;for airlines,a SAF use condition is added starting in 2030(European Commission,2023).These rules have been legally challenged by nongovernmental organizations,which argue they fail to adequately inform investors of

26、the climate impact of aviation(Opportunity Green,2024).Aircraft manufacturers have set corporate goals to support these decarbonization pathways.Some,including Airbus,Boeing,and Embraer,have begun to disclose Scope 3 emissions from their annual deliveries.Airbus has a short-term goal to reduce Scope

27、 3 greenhouse gas(GHG)emissions by 46%by 2035 using mitigation strategies like SAF and increased fuel efficiency(Airbus,2023b).Boeing and Embraer have both committed to supporting the aviation sectors net-zero 2050 target but have not yet set Scope 3 emissions targets.Airbus,Boeing,and Embraer have

28、all set goals to produce aircraft with 100%SAF capability by 2030,with aircraft now in the testing phase(Boeing,2023b;Airbus,2023c;Embraer,2021).In 2023,there were an estimated 23,689 in-service commercial passenger and freighter aircraft at varying stages of their lifetimes(International Bureau of

29、Aviation,2024).Each year,this fleet sees retirement of active aircraft at the end of their lifetimes,deliveries for fleet renewal,and additional deliveries to serve traffic growth.Over the next 20 years,manufacturers expect to deliver more than 40,000 new aircraft to support fleet renewal and traffi

30、c growth(Insinna,2023).Given these aggressive delivery targets and the long operational lifetimes of aircraft,it is key to consider the lifetime emissions from the existing and future fleet when assessing the compatibility of the industrys trajectory with net-zero pathways(Airbus,2023d).SAFs are und

31、erstood to be the most important way to reduce aircraft emissions,making up more than 50%of most decarbonization trajectories(Aerospace Technology Institute&Airports Council International,2022).However,aircraft today cannot use 100%SAFs due to safety and engine compatibility issues and are currently

32、 only certified to use SAF blends of up to 50%.As engine and airframe manufacturers continue the testing and production of new aircraft,it is essential for new deliveries to be compatible with alternative fuels,be they 100%SAFs,hydrogen,or electricity,to make meaningful progress toward lowering emis

33、sions.In this paper,we project committed emissions from the existing(2023)fleet and lifetime emissions from new(2024+)aircraft deliveries from Boeing,Airbus,and Embraer to evaluate how original equipment manufacturers(OEMs)can contribute to the net-zero goal.First,we present our modeling framework a

34、nd assumptions for various mitigation scenarios on opposite ends of the ambition scale.We then present our findings,highlighting when a net-zero carbon budget will be exhausted by new deliveries under each scenario.We also explore the allowable delivery volumes enabled by these technology pathways a

35、nd the volumes of carbon dioxide removal(CDR)needed for residual emissions.We close with recommendations for OEMs and ideas for future work.METHODOLOGYIn this analysis,we project the fleet evolution and lifetime emissions of both the in-service fleet and deliveries of conventional aircraft from 2024

36、 to 2042,as derived from 4ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETmanufacturer forecasts.We define conventional aircraft as those that operate on fossil jet fuel or SAF blends(100%SAF).Each year,Boeing,Airbus,and Embraer release market projections which deta

37、il deliveries,demand growth,and fleet dynamics over the coming decadesthe Boeing Commercial Market Outlook(CMO),Airbus Global Market Forecast(GMF),and Embraer Market Outlook,respectively(Boeing,2023a;Airbus,2023a;Embraer,2023).The most recent forecasts project expected deliveries by manufacturers th

38、rough 2042,and those were used in this study to estimate deliveries.Aircraft retirements were estimated using survival and activity curves to age existing fleet and replace aircraft as they go out of service.The aircraft delivered for traffic growth were estimated to be the additional number of airc

39、raft needed to grow the global fleet by 3.2%annually starting from 2023,as projected by the Boeing CMO.2We quantified lifetime emissions from the global fleet in mitigation scenarios of varying ambition and compared those results to aviation carbon budgets based on these forecasted deliveries.In the

40、 Baseline Scenario,CO2 emissions from conventional aircraft deliveries through 2042 were projected assuming limited technological improvement to identify the earliest delivery year by which the aviation carbon budget will be exhausted.The optimistic scenarios use a layered approach to applying decar

41、bonization measures to identify the latest year by which all new deliveries of conventional aircraft will need to be zero-emission to maintain the aviation carbon budget.First,we applied SAF(Optimistic SAF)alone to the in-service fleet and deliveries through 2042 and assess the lifetime emission red

42、uctions.Then,we added aggressive fuel efficiency improvements(Optimistic SAF+Fuel Efficiency)to quantify how these two measures contribute to the fleets emission reductions.A tank-to-wake(TTW)“net-zero”aviation carbon budget of 18.4 billion tonnes(Gt)was defined for the years 20222050 by taking an a

43、verage of four decarbonization pathwaysthe Mission Possible Partnerships Optimistic Renewable Electricity and Prudent Scenarios,Waypoint 2050,and the International Council on Clean Transportations(ICCT)Aviation Vision 2050 Breakthrough scenario converted to TTW(Mission Possible Partnership,2022;Air

44、Transport Action Group,2021;Graver et al.,2022).To align this net-zero budget with global temperature targets,1.5 C and 2 C carbon budget scenarios were derived as sensitivity analyses using the Intergovernmental Panel on Climate Changes(IPCC)AR6 pathways(IPCC,2022).Assuming a constant 2.4%share of

45、the global carbon budget for the sector,TTW carbon budgets of 8.3 Gt and 26.2 Gt were calculated for aviation to remain on the path for these temperature targets.Committed emissions from the existing fleet were estimated using the 2023 global passenger and freight aircraft breakdown as reported by I

46、nternational Bureau of Aviation(2024),as shown in Table 1.2 The projected fleet growth rate(3.2%)is slower than the traffic growth rate(3.7%)because the latter incorporates an expected 0.5%annual increase in passengers carried per flight.5ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A N

47、ET-ZERO CARBON BUDGETTable 1Breakdown of existing fleet and representative aircraft types,2023Aircraft classRegional jetNarrowbody passengerWidebody passengerFreighterNumber of aircraft3,20717,0213,8411,559Average age(years)15.011.511.819.6Representative aircraft typesEmbraer 175Boeing 737-800Airbus

48、 A320Boeing 787-9Airbus A330-200Airbus A330-200 FreighterBoeing 777 FreighterData source:International Bureau of Aviation(2024)The following methodology was used to calculate committed emissions from the existing fleet,made up of conventional aircraft.First,representative aircraft types were identif

49、ied within the fleet for each aircraft class as indicated in Table 1.Then,the average CO2 emitted per hour was calculated for representative aircraft types within each aircraft class as shown in Equation 1.Aircraft CO2 emissions(kghour)=Mission Speed kmhour Fuel Burn kgkm Fuel Specific Energy MJkg T

50、TW Fuel Carbon Intensity kg CO2MJ (1)Average speed was calculated using flight movement data from the Airline Data Incs 2022 database and fuel burn per kilometer by representative aircraft type was extracted from the ICCTs GACA 2019 dataset(Graver et al.,2020).Mission speed,which is the average spee

51、d over ground during take-off,cruise,approach,and landing,but not including taxi time,was used in this analysis.3A specific energy of 42.8 megajoule per kilogram(MJ/kg)was used for jet fuel and the TTW average fuel carbon intensity of SAFs was extracted from the ICCTs PACE model(Breakthrough Scenari

52、o)for the Optimistic SAF Scenario.In the Baseline Scenario,the fuel mix remained 100%Jet A over the lifetime of all delivered aircraft to reflect the fuel carbon intensity with no SAF use.4 In the Optimistic SAF case,SAFs were introduced into the fuel mix following ReFuelEU SAF mandate volumes,start

53、ing at 2%of the blend in 2025 and increasing to 70%by 2050(Regulation 2023/2405).This scenario assumes a global rollout of the RefuelEU SAF mandate.In reality,SAF use will likely vary across regions,with some countries lagging in policies needed to ensure necessary volumes and low life-cycle GHG emi

54、ssions.The global fuel carbon intensity for the Baseline and Optimistic SAF Scenarios through 2050 is shown in Figure 1.On a TTW basis,the average carbon intensity of jet fuel in the Baseline case stays constant at 73.16 gCO2/MJ,while under the Optimistic SAF case it falls to about 30 gCO2/MJ in 205

55、0.53 Average speed for a specific aircraft type was calculated as an average of the total distance flown divided by the total airtime in 2022 from the Airline Data Inc.database.Because aircraft speeds are slower during the landing and take-off(LTO)cycle and approach,mission speeds are,on average,slo

56、wer than cruise speeds.4 In 2023,an estimated 99.8%of commercial jet fuel use was derived from fossil fuels;SAFs accounted for only 0.2%(IATA,2024b).Due to their high cost typically between two and five times that of fossil jet fuel uptake of SAF is expected to remain low in the absence of policy su

57、pport.5 The well-to-wake(WTW)GHG emissions of the global fuel mix was converted to TTW CO2 to align with net-zero carbon budgets.On a WTW basis,the global jet fuel mix in our Aggressive case would be 70%SAF in 2050 with a WTW CO2 of 36 g CO2/MJ.Because SAF emissions are greater than zero on a WTW ba

58、sis,we adjust the TTW GHG savings proportionally to reflect the overlap between system boundaries for Scope 3 emissions.Thus,for a SAF with 90%GHG savings compared to fossil jet fuel,we attribute a 90%emissions reduction in WTT and TTW emissions,respectively,though the TTW emissions would be treated

59、 as zero in conventional GHG accounting.6ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETFigure 1Global aviation fuel carbon intensity scenarios(tank-to-wake)20252030203520402045205001530456075Fuel carbon intensity(gCO2/MJ)OptimisticBaselineTHE INTERNATIONAL COUNCIL

60、 ON CLEAN TRANSPORTATION THEICCT.ORGTable 2 indicates the average mission speed and fuel burn for each of the representative aircraft types in the existing fleet.Mission speeds vary from about 440km per hour for a regional jet up to more than 700 km per hour for a large widebody aircraft.On average,

61、larger aircraft fly longer missions and,therefore,spend more time in cruise relative to smaller aircraft,thus increasing their average speed.Fuel burn ranges from about 3 kg per kilometer for the Embraer 175 aircraft up to more than 10 kg per kilometer from the Boeing 777 Freighter.Table 2Representa

62、tive aircraft types,average mission speed,and average fuel burn for fleet delivered prior to 2024Aircraft classAircraft typeMission speed (km/hour)Average fuel burn(kg/km)Regional jetEmbraer 1755052.92NarrowbodypassengerBoeing 737-8005663.98Airbus A3206163.98WidebodypassengerBoeing 787-96666.34Airbu

63、s A330-2007167.27FreighterpassengerAirbus A330-2007168.51Boeing 77772410.7Each representative aircraft types lifetime emissions were then calculated as a product of the CO2 emitted per hour,activity hours by age,number of aircraft,and survival summed over the course of its useful lifetime(Equation 2

64、).Activity and survival curves were derived from Singh and Rutherford(2011),and are shown in Figures 2 and 3.A 7ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETsteep decline in both survival rates and activity hours can be seen after about 20 years of age across air

65、craft classes.Figure 2Survival curves by aircraft class01020304050Aircraft age(years)020406080100Percentage of aircraft in serviceNarrowbody passenger aircraftWidebody passenger aircraftLarge freighter aircraftTHE INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION THEICCT.ORGFigure 3Activity curves by ai

66、rcraft class010203040Aircraft age(years)1,5001,0002,0002,5003,0003,5004,0004,500Annual activity hours per yearNarrowbody aircraftWidebody passenger andlarge freighter aircraftTHE INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION THEICCT.ORG8ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET

67、-ZERO CARBON BUDGET Lifetime CO2=a1 na CO2hour t0 hoursyear%of surviving aircraft(2)Where:a is each representative aircraft typena is number of aircraft for each representative aircraft typet is the year in operationThis calculation for in-service aircraft was repeated to calculate committed CO2 emi

68、ssions from 2022 aircraft deliveries from Boeing,Airbus,and Embraer.This allows for our model to be compared against each manufacturers reported Scope 3 emissions.Starting in 2024,the representative aircraft types used were the most advanced aircraft model in each category to better reflect the fuel

69、 burn of new aircraft being delivered today.Table 3 shows the representative aircraft types,average speeds,and average fuel burn rates used for projected deliveries of conventional aircraft from 2024 to 2033 in both scenarios.6Table 3Representative aircraft types,mission speed,and average fuel burn

70、for 2024-2033 deliveriesAircraft typeMission speed(km/hour)Fuel burn(kg/km)Embraer 190 E25133.17Boeing 737-MAX6153.36Airbus A320neo6163.29Boeing 7876656.17Airbus A330-900neo6416.65Airbus A330-300 Freighter7397.52Boeing 777 Freighter72410.7Deliveries were projected by applying a survival curve to eac

71、h years in-service fleet to derive retirements,and calculating the additional aircraft needed to support an average fleet growth rate of 3.2%per year from 2024.The most advanced representative aircraft types currently in service(those seen in Table 3)were used until 2033.Starting in 2034,two differe

72、nt approaches were taken.In the Baseline Scenario,which assumes limited technology uptake,the representative aircraft summarized in Table 3 were used through 2042.In the Optimistic SAF+Fuel Efficiency Scenario,we added a second mitigation technology into our modeling.Starting in 2034,advanced fuel-e

73、fficient aircraft were modeled using the“Aggressive”fuel efficiency improvement scenario in Kharina et al.(2016).These new aircraft types were phased into new aircraft deliveries over the course of 6 years beginning in 2034,increasing in the share of deliveries annually by 16.67%.Accordingly,startin

74、g in 2039,all new deliveries are assumed to be these“Aggressive”technology aircraft.Since Kharina et al.(2016)does not model freighters,and technological advancements on freighter aircraft are often slower to market,a constant annual 1.04%fuel efficiency improvement was applied to new freighters in

75、the Optimistic SAF+Fuel Efficiency Scenario.Table 4 summarizes 6 Where the average speed for an aircraft type was unavailable,the average speed of a comparable aircraft within the same aircraft family was used.9ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETthe spe

76、ed and fuel burn assumptions used for future deliveries(2034+)of conventional aircraft in the Optimistic SAF+Fuel Efficiency Scenario.Table 4Aircraft class,average speed and average fuel burn for the Optimistic SAF+Fuel Efficiency Scenario(2034+)Aircraft classMission speed(km/hour)Fuel burn(kg/km)Re

77、gional jet5151.94Passenger narrowbody6162.16Passenger widebody6954.49Freight widebody7241.04%p.a.improvement from Baseline In these scenarios,the lifetime emissions from each years deliveries were calculated as a product of the fuel burn,fuel CO2 intensity,activity hours,and survival curves and adde

78、d to the emissions of the in-service fleet.This total was compared with the aviation carbon budget to identify the delivery year by which the budget is fully consumed.RESULTSIn this section,we present the key findings from our analysis.First,we compare our modeled committed emissions from 2022 deliv

79、eries to those provided by OEMs in their Scope 3 reporting.Next,we present our estimate of committed emissions from the 2023 in-service fleet.We then summarize the potential lifetime emission reductions from new aircraft by delivery year across the Baseline and Optimistic Scenarios.We then compare p

80、rojected emissions under both scenarios with various(net-zero,1.5 C,and 2 C)carbon budgets to determine when all new aircraft need to become zero emission throughout their operational lifetimes to meet climate targets.We also quantify the amounts of CDR required to address residual emissions in each

81、 of these scenarios through 2042.We close by analyzing how mitigation measures enable manufacturers to meet their net-zero goals and delivery targets.COMPARISON WITH REPORTED 2022 SCOPE 3 EMISSIONSTo validate our modeling framework,we first calculated the committed CO2 emissions of 2022 deliveries f

82、rom Airbus,Boeing,and Embraer and compare these with the respective reported Scope 3 GHG emissions.For a consistent comparison,we compared each OEM estimate,which assumes a worst-case“no-SAF”future,with the lifetime emissions from 2022 deliveries calculated in our Baseline case.7 Table 5 compares th

83、ese results.7 Scope 3 emissions from 2023 deliveries have not yet been reported by OEMs,so reported values from 2022 deliveries were used for comparison with our model.10ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETTable 5Comparison of reported and modeled well-t

84、o-wake Scope 3 emissions from 2022 deliveriesManufacturerManufacturer estimate(Mt CO2e)ICCT model estimate(Mt CO2e)Difference(ICCT versus manufacturer)Boeing363455+25%Airbus494490-1%Embraer15.653+240%Total873998+14%Overall,we found agreement between our modeling of projected emissions for 2022 deliv

85、eries with OEM estimates of Scope 3 emissions from Boeing and Airbus,after converting our results to well-to-wake emissions.8 Our estimate of projected emissions from Airbus deliveries is essentially identical to their estimates,while our estimates for Boeing are about 25%higher.Our emissions estima

86、te for Embraer deliveries is more than triple that provided by Embraer.It is unclear what drives this,but it can likely be attributed to differences in modeling assumptions including aircraft survival,activity hours,and representative aircraft types.These differences highlight the value of developin

87、g a standardized methodology for manufacturer calculations of Scope 3 emissions,as variance in methodology makes it difficult to compare emission estimates.COMMITTED EMISSIONS FROM THE IN-SERVICE FLEETUsing this methodology,both committed emissions from the current in-service fleet and projected emi

88、ssions from future deliveries could be assessed.The emissions of the in-service fleet(9.1 Gt)are broken down by manufacturer and aircraft class in Figure4.9 More than half the committed emissions of the existing fleet come from narrowbody passenger aircraft,followed by widebody passenger aircraft(32

89、%),freighters(12%),and regional jets(4%).This is due to factors such as the volumes,activity curves,and survival curves of the different aircraft types in the fleet.Figure 4Committed emissions from the 2023 in-service fleet by aircraft class(left)and manufacturer(right),Baseline ScenarioBoeing48.3%A

90、irbus47.1%Embraer2.8%Other1.8%Single aisle51.9%Widebody31.5%Freighter12.3%Regional jet4.3%THE INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION THEICCT.ORG8 In this study,emissions were calculated on a TTW basis to align with net-zero trajectories.On a well-to-wake basis,emissions are about 18%higher th

91、an TTW emissions due to energy use in upstream fuel production.9 This breakdown assumes no SAF use,per the Baseline Scenario.However,it would remain almost identical in the Optimistic SAF Scenario given the limited SAF uptake throughout the lifetime of the in-service fleet.11ICCT WORKING PAPER|LIFET

92、IME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETWhen considering the breakdown by manufacturer,the vast majority of emissions(over 95%)from the fleet can be attributed to Boeing and Airbus aircraft.This is due to the volume of commercial aircraft produced by these two manufacturers;in the

93、current passenger fleet,they make up over 95%of existing narrowbody,widebody,and freighter aircraft.PROJECTED LIFETIME EMISSIONS FROM FUTURE DELIVERIESComparison of the projected lifetime emissions from conventional aircraft by delivery year across the Baseline and Optimistic Scenarios indicate a su

94、bstantial potential to reduce emissions from SAF use and fuel efficiency improvements(Figure 5).Under the Baseline Scenario,projected emissions from new deliveries increase consistently through 2040.The Optimistic Scenarios still show steady emissions growth over the next decade;however,the lifetime

95、 emissions of each years deliveries are below the Baseline Scenario because aggressive decarbonization measures are in place.The impact of individual mitigation technologies can be seen when comparing the Optimistic SAF and Optimistic SAF+Fuel Efficiency Scenarios,as emissions reduction is maximized

96、 with the aggressive use of both SAFs and fuel efficiency improvements.In 2034,emissions from new deliveries start to fall due to greater amounts of SAF in the fuel mix and the introduction of new aircraft types.By 2039,a gradual drop can be seen in the lifetime emissions of new deliveries because a

97、ll deliveries are assumed to be new,more efficient aircraft types(as shown in Table 4)operating on over 60%SAF throughout their lifetimes.This result can be viewed as the maximum potential for conventional aircraft given the challenge of introducing both radically more fuel-efficient aircraft types

98、starting in 2034 and the use of ReFuelEU volumes of SAFs globally.Cumulative CO2 from new conventional aircraft delivered between 2024 and 2042 would be cut by more than 50%from 29 Gt to 14 Gtunder the Optimistic SAF+Fuel Efficiency Scenario.Figure 5Projected lifetime emissions for new aircraft by d

99、elivery year and scenario,20242042 2024202620282030203220342036203820402042Delivery year03006009001,2001,5001,8002,100Lifetime emissions(Mt CO2)BaselineOptimistic SAFOptimistic SAF+Fuel EfciencyTHE INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION THEICCT.ORG12ICCT WORKING PAPER|LIFETIME EMISSIONS FROM

100、AIRCRAFT UNDER A NET-ZERO CARBON BUDGETOur findings highlight the need to scale up SAF use and improve fuel efficiency over the coming decade,as the projected lifetime emissions from each years deliveries would increase annually(shown in Figure 5)due to anticipated fleet growth.10 For these deliveri

101、es to substantially reduce their projected lifetime emissions and limit emissions growth,the introduction of SAF and other measures is necessary.Even greater ambition will be required for new aircraft delivered in the 2030s.COMPARISON WITH CARBON BUDGETSIn the conservative Baseline Scenario,the shar

102、e of fossil jet fuel remains constant at 100%of the fuel mix.As stated,the net-zero aviation carbon budget was assumed to be 18.4 Gt;the 1.5 C and 2 C budgets are 8.3 and 26.2 Gt,respectively.The emissions associated with aircraft in service in 2023 consume almost 50%of the net-zero budget,as they m

103、ake up the largest portion of the fleet and consequently require the most fuel over their lifetime.Added to that,the projected lifetime emissions of conventional aircraft delivered through 2032 would fully deplete the carbon budget(Figure 6).The low(1.5 C)carbon budget is consumed just by committed

104、emissions from the in-service fleet,while the high(2 C)carbon budget is consumed by lifetime emissions of deliveries through 2038.Figure 6Consumption of aviation carbon budget from cumulative lifetime emissions of projected fleet20252023and before20302035Year20402045205001020304050Cumulative lifetim

105、e CO2 emissions(Gt)Committed emissions of in-service fleetBaselineOptimistic SAF+Fuel Efciency1.5 C carbon budgetNet-zero carbon budget2 C carbon budget203220372038THE INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION THEICCT.ORGFigure 6 also shows the cumulative lifetime emissions trajectory for delive

106、ries with the deployment of SAF and aggressive fuel efficiency improvements(Optimistic SAF+Fuel Efficiency).In this case,these measures delay the year by which the net-zero 10 The reported 2022 deliveries from Airbus,Boeing,and Embraer are higher than annual deliveries estimated by our model through

107、 2028.Some real-world variation from the modeled delivery estimates is expected due to uncertainty in order fulfillment,backlog,and usage cycles.13ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETaviation carbon budget is fully consumed by the lifetime emissions of n

108、ew deliveries from 2032 to 2037.After that time,any emissions from new conventional aircraft that are not removed by CDR would exceed the available carbon budget and,therefore,be incompatible with a net-zero goal.As with the Baseline Scenario,under both Optimistic Scenarios,the 1.5 C aviation carbon

109、 budget is depleted by the in-service fleet.However,in the Optimistic SAF+Fuel Efficiency Scenario,the 2 C carbon budget is not depleted by deliveries through 2042.To model a 2 C carbon budget,we maintained the fleet growth assumptions and technology deployment of the Optimistic SAF+Fuel Efficiency

110、Scenario until the budget was fully consumed,which in this case occurs in 2053.This indicates the need for potentially deploying other measures,such as CDR and non-CO2 mitigation,to supplement the strategies implemented.We also calculated the volumes of CDR in the form of direct air capture(DAC)that

111、 would be needed to remove CO2 emissions from projected aircraft deliveries through 2042 after the net-zero carbon budget is exhausted.In the Baseline Scenario,we estimate that about 22 Gt of DAC will be needed to capture the lifetime CO2 emissions of aircraft delivered through 2042.11 In the Optimi

112、stic SAF+Fuel Efficiency Scenario,we estimate that about 5 Gt of DAC will be needed under the net-zero budget.This is on the order of 2,500 times the global capacity of DAC facilities currently under construction or in advanced stages of development for use by all industries in 2030(International En

113、ergy Agency,2024).12Collectively,these findings suggest that,between 2032 and 2037,all new aircraft must be net-zero aircraft,defined here as either ZEPs or aircraft operating on 100%low-carbon SAF,over their operational lifetimes for airlines to achieve net-zero emissions in 2050.In other words,man

114、ufacturers must go net-zero about 15 years before airlines.After that time,all newly delivered aircraft must be fueled by 100%SAFs,hydrogen,or electricity,all with very low life-cycle emissions,or have their emissions fully removed using widescale CDR,for airlines to meet their climate goals.13This

115、study also explored the potential market for conventional versus net-zero aircraft.Figure 7 shows the breakdown of OEM projected deliveries(far left)through 2042 under a net-zero budget,divided by conventional and net-zero aircraft for our two scenarios.We estimate that OEMs could only deliver about

116、 24,000 conventional aircraft,or about 62%of projected deliveries,under the Baseline Scenario.The remaining 14,500 aircraft would need to be net-zero throughout their lifetimes in order to meet the 2050 net-zero goal.Under the Optimistic SAF+Fuel Efficiency Scenario,an additional 4,500 conventional

117、aircraft could be delivered because the use of SAF blends and aggressive fuel efficiency improvements would economize on the available carbon budget.Even then,manufacturers will need to deliver at least 10,000 net-zero aircraft powered by hydrogen,electricity,or 100%SAF by 2042.14 All new aircraft d

118、elivered after 2042 would also need to be net-zero.11 Additional removals would be required for deliveries made between 2043 and 2050,which was not modeled in this exercise.12 The International Energy Agencys projection for global CO2 capture by direct air capture is about 2.5 million tonnes in 2030

119、 when considering facilities in the construction and advanced development phases.13 Although in lower volumes than with fossil jet fuel,CO2 is still emitted from the combustion of 100%SAF.Some CO2 removal will be required for new deliveries to be zero-emissions and the carbon budget to be maintained

120、.14 This approach,which does not consider deliveries from 20432050,provides a conservative estimate of the impact of the net-zero goal on new aircraft deliveries.This is because aviations net-zero carbon budget through 2050 is being exhausted by deliveries before 2042.14ICCT WORKING PAPER|LIFETIME E

121、MISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETFigure 7Projected deliveries and breakdown of allowable deliveries under net-zero budget by scenario,20242042OEM projected deliveriesOptimistic/Net-zeroBaseline/Net-zero05,00010,00015,00020,00025,00030,00035,00040,000Total aircraft deliveries(2024

122、2042)Conventional aircraftZero-emission aircraftTHE INTERNATIONAL COUNCIL ON CLEAN TRANSPORTATION THEICCT.ORGCONCLUSIONSThis analysis explored how aircraft production,sales,and usage cycles are linked to airline emissions.We compared two categories of emissions with a net-zero carbon budget of 18.4

123、Gt:committed emissions from aircraft already in service in 2023,and projected lifetime emissions from new conventional aircraft deliveries through 2042.Todays in-service fleet is expected to emit about 9 Gt of CO2 over the remainder of their useful lives,or almost 50%of a net-zero carbon budget and

124、the entirety of a 1.5 C carbon budget.Under a conservative Baseline Scenario with limited technology uptake,aviation emissions are projected to increase linearly,doubling by 2035 due to fleet growth.Projected emissions from new deliveries of conventional aircraft would then fully deplete a net-zero

125、aviation carbon budget in 2032.Concentrated investments in SAFs and new aircraft fuel efficiency technologies can dramatically cut projected CO2 emissions from new deliveries of conventional aircraft.Under the Optimistic SAF+Fuel Efficiency Scenario with substantial SAF uptake and aggressive fuel ef

126、ficiency improvements from new aircraft types,the projected lifetime emissions of total new deliveries would fall more than 50%,from 29 Gt to 14 Gt,by 2042.Still,due to traffic growth,we project a net-zero aviation carbon budget would be depleted by new aircraft deliveries by 2037 under the Optimist

127、ic SAF+Fuel Efficiency Scenario.Thus,while SAF blending and efficiency improvements can substantially cut projected emissions from the fleet,additional action will be needed from aircraft manufacturers to transition away from fossil fuels by the mid-2030s.15ICCT WORKING PAPER|LIFETIME EMISSIONS FROM

128、 AIRCRAFT UNDER A NET-ZERO CARBON BUDGETRECOMMENDATIONSAircraft manufacturers could consider dramatically increasing investments in clean aviation technologies to reduce CO2 emissions,notably ZEPs.Our modeling suggests that there will be a substantial market for aircraft that are net-zero over their

129、 lifetimesbetween 10,000 and 14,500 units through 2042,depending on SAF and fuel efficiency uptake.Specifically,our conclusions point to three recommendations for manufacturers to consider:1.Accelerate efforts to develop narrowbody ZEPs,especially those powered by hydrogen,that emit no CO2 during op

130、eration.2.Ensure that all new aircraft can burn 100%SAF,not just SAF blends,starting in 2030.3.Establish stringent Scope 3 emission targets requiring that the aircraft delivered will emit less CO2 emissions over their lifetimes.First,regarding ZEPs,we recommend that manufacturers accelerate efforts

131、to develop hydrogen and electric aircraft.Since the range and capacity of the latter are expected to be low,priority should be placed on bringing liquid hydrogen combustion narrowbody aircraft into service by 2035(Mukhopadhaya&Rutherford,2022;Airbus,2020).Electric aircraft may play a minor role in s

132、pecific applications,including commuter aircraft,electric vertical take-off and landing(eVTOL)aircrafts,and for training purposes(Mukhopadhaya&Graver,2022).Regional hydrogen aircraft powered by fuel cells,either retrofits or clean sheet designs,may enter service faster than liquid hydrogen combustio

133、n aircraft and can be used to scale aviation hydrogen infrastructure.However,given that most projected emissions in the coming decades are from narrowbody aircraft,manufacturers should accelerate the development and entry of hydrogen combustion narrowbody aircraft into the fleet.Second,in the near-t

134、erm SAF will continue to be used in diffuse blends(0.5%global average)at airports.Still,manufacturers must consider the compatibility of their aircraft deliveries with 100%SAF,as many aircraft delivered today will remain in-service through 2050.Given the ongoing development and gradual introduction

135、of new aircraft types,deliveries are expected to be a mix of new and legacy aircraft,and there is a long road ahead before all new aircraft will be able to use 100%SAF upon delivery.The constraint of jet fuel availability becomes more prevalent as the SAF percentage in the fuel mix increases,so airc

136、raft manufacturers should consider prioritizing the rapid introduction of fully SAF-compliant aircraft and integrating this capability into existing engines with the necessary upgrades,while ensuring safety standards.Finally,this analysis suggests that for airlines to achieve net-zero CO2 emissions

137、in 2050,manufacturers will need to achieve net-zero Scope 3 emissions from their deliveries around 2035.This implies that all manufacturers of commercial aircraft and jet engines should set a 100%Scope 3 emission reduction target in 2035.Since all alternative fuels,including hydrogen,electricity,and

138、 SAFs,have residual emissions associated with fuel production,a negative emission technology such as CDR will be required to meet these targets.POTENTIAL FUTURE RESEARCHThis study investigated Scope 3 emissions from new aircraft deliveries in relation to aviation climate targets.It took a global app

139、roach focusing on two of the most important technologies for decarbonizing aviation SAFs and advanced fuel-efficient aircraft.Future expansion of this research can include the impacts of projected fleet evolution on non-CO2 forcers.Another potential area of study is to consider global 16ICCT WORKING

140、 PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETfleet renewal and growth from a regional perspective.Committed emissions from the in-service fleet are likely dominated by airlines in developed economies,while rapidly growing airlines in emerging economies may contribute more to

141、 projected emissions.The growth of lifetime emissions could then be assessed from an equity lens,as there is significant regional variation in projected aircraft deliveries over the next two decades.17ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETREFERENCESAerospa

142、ce Technology Institute&Airports Council International.(2022).Integration of sustainable aviation fuels into the air transport system.https:/www.ati.org.uk/wp-content/uploads/2022/06/saf-integration.pdfAirbus.(2020,September 20).ZEROe.https:/ annual report 2022.https:/ global market forecast.https:/

143、 3 disclosure:Reducing emissions from our products in-service and our supply chain.https:/ aviation fuel:Advancing the ecosystem for a proven alternative fuel.https:/ life:From delivery to service retirement.https:/ aviation fuels:A new generation of reduced emissions fuels.https:/ Transport Action

144、Group.(2021).Waypoint 2050.https:/aviationbenefits.org/media/167187/w2050_full.pdfBoeing.(2023a).Boeing commercial market outlook.Boeing CMO.https:/ doubles sustainable aviation fuel purchase for commercial operations,buying 5.6 million gallons for 2023 Press release.https:/ Boeing.(2023c).Sustainab

145、le aviation fuel(SAF).https:/ Corporate Data Accountability Act.Cal.SB 253.(2023).https:/leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202320240SB253 Embraer.(2021).Right for sustainability.https:/ market outlook.https:/ Commission.(2023).EU taxonomy:Manufacturing of aircraft.https:/

146、ec.europa.eu/sustainable-finance-taxonomy/activities/activity/286/viewDirective(EU)2022/2464 of the European Parliament and of the Council of 14December 2022 amending regulation(EU)No537/2014,Directive 2004/109/EC,Directive 2006/43/EC and Directive 2013/34/EU,as regards corporate sustainability repo

147、rting.OJ L 322,1580(2022)https:/eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32022L2464Graver,B.,&Rutherford,D.(2021).Low-cost carriers and U.S.aviation emissions growth,2005 to 2019.International Council on Clean Transportation.https:/theicct.org/publication/low-cost-carriers-and-u-s-aviatio

148、n-emissions-growth-2005-to-2019/Graver,B.,Rutherford,D.,&Zheng,X.S.(2020).CO2 emissions from commercial aviation:2013,2018,and 2019.International Council on Clean Transportation.https:/theicct.org/publication/co2-emissions-from-commercial-aviation-2013-2018-and-2019/Graver,B.,Zheng,S.,Rutherford,D.,

149、Mukhopadhaya,J.,&Pronk,E.(2022).Vision 2050:Aligning aviation with the Paris Agreement.International Council on Clean Transportation.https:/theicct.org/publication/global-aviation-vision-2050-align-aviation-paris-jun22/Insinna,V.(2023,June 17).Boeing boosts 20 year outlook for planes due to narrowbo

150、dy demand.Reuters.https:/ Air Transport Association.(2024a).Aviation net-zero CO2 transition pathways:Comparative review.https:/www.iata.org/contentassets/8d19e716636a47c184e7221c77563c93/nz-roadmaps.pdfInternational Air Transport Association.(2024b).Net zero 2050:Sustainable aviation fuels.https:/w

151、ww.iata.org/en/iata-repository/pressroom/fact-sheets/fact-sheet-alternative-fuels/International Bureau of Aviation.(2024).IBA Insights:Fleets Module Dataset dataset.https:/insightiq.iba.aero18ICCT WORKING PAPER|LIFETIME EMISSIONS FROM AIRCRAFT UNDER A NET-ZERO CARBON BUDGETInternational Energy Agenc

152、y.(2024).CO2 capture by direct air capture,planned projects and in the Net Zero Emissions by 2050 Scenario.https:/www.iea.org/energy-system/carbon-capture-utilisation-and-storage/direct-air-captureIntergovernmental Panel on Climate Change.(2022).IPCC Sixth Assessment Report,Chapter 3:Mitigation path

153、ways compatible with long-term goals.https:/www.ipcc.ch/report/ar6/wg3/chapter/chapter-3/Kharina,A.,Rutherford,D.,&Zeinali,M.(2016).Cost assessment of near-and mid-term technologies to improve new aircraft fuel efficiency.International Council on Clean Transportation.https:/theicct.org/publications/

154、cost-assessment-near-and-mid-term-technologies-improve-new-aircraft-fuel-efficiencyMission Possible Partnership.(2022).Making net-zero aviation possible:An industry-backed,1.5C-aligned transition strategy.https:/www.missionpossiblepartnership.org/action-sectors/aviation/Mukhopadhaya,J.,&Graver,B.(20

155、22).Performance analysis of regional electric aircraft.International Council on Clean Transportation.https:/theicct.org/publication/global-aviation-performance-analysis-regional-electric-aircraft-jul22/Mukhopadhaya,J.,&Rutherford,D.(2022).Performance analysis of evolutionary hydrogen-powered aircraf

156、t.International Council on Clean Transportation.https:/theicct.org/publication/aviation-global-evo-hydrogen-aircraft-jan22/Opportunity Green.(2024,April 16).NGOs launch legal challenge against EUs bid to label fossil fuel planes and ships as green Press release.https:/www.opportunitygreen.org/press-

157、release-eu-taxonomy-challenge#:text=The%20Taxonomy%20is%20meant%20to,2030%20and%202050%20climate%20goalsRegulation(EU)2023/2405 of the European Parliament and of the Council of 18 October 2023 on ensuring a level playing field for sustainable air transport(ReFuelEU Aviation).OJ L 2405,1(2023).http:/

158、data.europa.eu/eli/reg/2023/2405/2023-10-31Rutherford,D.&Singh,N.(2011).Projection of Aviation Energy Use and Related Characteristics Consultant report to Argonne National Laboratory.U.S.Environmental Protection Agency.(2020a).Greenhouse gas inventory guidance:Direct emissions from mobile combustion

159、 source.https:/www.epa.gov/sites/default/files/2020-12/documents/mobileemissions.pdfU.S.Environmental Protection Agency.(2020b).Greenhouse gas inventory guidance:Indirect emissions from purchased electricity.https:/www.epa.gov/sites/default/files/2020-12/documents/electricityemissions.pdfU.S.Securit

160、ies and Exchange Commission.(2024).The enhancement and standardization of climate-related disclosures for investors.https:/www.sec.gov/rules/2022/03/enhancement-and-standardization-climate-related-disclosures-investorswww.theicct.org communicationstheicct.orgtheicct.org B E I J I N G|B E R L I N|N E W D E L H I|SA N F R A N C I S CO|SO PAU LO|WAS H I N GTO N D C