What does Net Zero mean for aviation?

Net Zero commitments are flourishing on many publications, speeches and advertising. Aviation is no exception. Back in Oct 2021, IATA announced the sector will reach Net Zero in 2050 (see note 1)

Let’s decrypt what does it really means and how a Net Zero aviation would look like.

What is Net Zero?

The concept of Net Zero is closely tied to the notion of carbon budget.(see http://captaincarbon.net/whats-a-carbon-budget-how-defining-a-carbon-footprint/).

Net Zero on human activities is achieved when the total of anthropic carbon emissions equal what the the Earth carbon sinks can absorb.

This means not exceeding a total emission of 22 Giga Tons of CO2 per year. To set orders of magnitude, human activities released more than 40 Gigatons of CO2 in the atmosphere in 2019. To stay simple, reaching Net Zero requires to cut overall carbon emissions by 2 and …..preserving carbon sinks!

Agenda for Global Net Zero

In July 2021, Europe disclosed its FIT for 55 package with the objective to reduce 1990’s level of carbon emissions by 55% in 2030 and to achieve Net Zero by 2050. Declining Net Zero objective for Europe would follow the same logic as the one proposed for aviation (below section.)

Net Zero declined for Aviation

Achieving Net Zero for a particular industrial sector is clearly a theoretical concept given Net Zero only makes sense at the Earth global scale. This statement applies even more for a specific company.

This being said, let try the challenge to propose a method declining Net Zero objectives for aviation. A fair way to do would be to define which portion of the Global Net Zero carbon budget (22 Gtons) the air transport can get. Not easy but a must do.

Total carbon emissions of the commercial aviation were about 1 Gtons in 2018 which represents 2,6% of the total anthropic ones.

Assuming commercial aviation has the same level of effort to accomplish than any others, it suffices to apply 2,6% to the Net Zero Global to get the Net Zero Commercial aviation. Fair enough!

That gives a not to exceed budget of 572 Mtons of CO2e for air transport (2,6*22/100=0,572 Giga Tons). Again, to be simple, it’s about cutting the current aviation carbon emissions by 2 within 30 years.

How big is the challenge?

If Net Zero were to be applied tomorrow with no further investment a simple way would be to divide air traffic by a factor 2. Putting Covid situation aside, this is not going to happen if IATA modeling of post pandemic traffic growth materializes (+3,3 % per year -See note 2).

Lifting tons of metal in the air, is by nature, an activity of predilection for constrained engineering. Aviation has constantly been achieving fuel efficiency gains (1,25% fuel burn reduction per yer in average). But in the same time, air transport has the fastest carbon emission growth.

Aviation carbon emission trend in Europe

Two main reasons can explain that trend. First: traffic growth has been overpassing fuel efficiency gains. Second is aviation’s addiction to fuel for its unbeatable energy density and transport/storage ability.

Compared to its competitors, Kerosene has the highest couple of Volumetric energy density & Massic storage efficiency.

Comparison of Energy vectors efficiency.

Decarbonization is indeed the biggest challenge aviation has ever taken…

How getting there?

Aircraft manufacturers, airlines, airports acknowledged the necessity to reduce carbon emissions of their operations and are working on various mitigation options. Below is a recap of the solutions currently available or in developments.

Efficiency gains: -10% by 2030

Deploying the efficiency gains currently available stand as the low hanging fruits. They are the quickest ones to implement (optimized ATM routes, maximized load factor, electrical power on Ground, formation flights, getting rid of Fuel tankering practices, etc) and would all together bring a one shot max 10% fuel savings by 2030 (Note 3)

Fleet renewal15% by 2045

Renewing current aged fleet with fuel efficient platforms has a 15% fuel burn reduction potential but would take not less than 25 years.

Electrification / hybridation: -5% by 2050

Unless battery technology goes into a revolution increasing their energy density tenfold, electrical planes will mots likely remain small in capacity and range. Application of choice would start in island hopping journeys and progressing to short domestic travels. Hybridation would stretch range a bit but not going beyond regional flights which represent 7% of total air travel emissions. Potential is estimated to be 5% of carbon emission reduction once deployed at full regional scale (70% savings on a 7% global share)

Hydrogen: Joker!

Airbus is currently working on an aircraft fueled with H2 would it be directly injected into a Jet engine or powering electrical motors thru fuel cells. A demonstrator is expected to fly by 2035. The technical challenge is as big as setting up the overall “Green” H2 supply chain. Most probably, the volume taken by Hydrogen tanks will limit H2 flights range to short / medium hauls. No one can forecast with a good confidence level what would be the extent of H2 fueled aircrafts within 2050 skies, time will tell…

SAF: -4,8 % in 2035

Sustainable Aviation Fuel (SAF) constitutes the most viable short term solution to decarbonize air transport given they can directly be blent with Jet A fuel in significant proportion (50%) with almost no Engine modifications. Two of them can be considered sustainable.

Second generation of SAFare not competing with crop lands as they are coming from feedstock including waste oil and fats. While they are sustainable and offer up to 80% decarbonization potential, they are not scalable. The ICCT considers 2nd Gen SAF could realistically provide 3,5% of 2035 Jet Fuel demand. (see note 4)

E-fuel (also called PTL) is combining captured CO2 with H2 to generate a synthetic fuel. To ensure E-fuel has a low carbon label, Hydrogen needs to be electrolyzed from a low carbon electrical source. Above 90 g of CO2 per kWh, burning E-Fuel releases more CO2 than Jet A fuel. To set orders of magnitudes, World carbon intensity of electricity is currently 500 g of C02 per kWh. (200 g for Europe, 60 g for France)

On paper, E-fuel has a high scalable potential and constitutes the most promising option. In reality, the need for low carbon electricity is huge and directly compete with growing demand of electrification for land mobilities & other low carbon applications. ICCT considers E-fuel could constitute not more than 0,5% of 2035 total aviation fuel volume.

ICCT SAF production forecast

All SAF together would provide 6% of total aviation fuel needs for a 4,8% decarbonation potential (80% effectiveness).

This projection aligns pretty well with the EU FIT for 55 package requiring SAF to be at 2% of Fuel demand in 2025 and 5% in 2030.

Done deal?

All added, the here above solutions would provide a potential to reduce carbon emission by 35%. Applied to current levels of aviation emissions, (1 Gtons of CO2), that gives 650 Mtons of CO2 which overpass the Net Zero budget (574 Mtons of CO2). Innovation & investments would need to be pushed a bit further to get that extra mile.

If we consider the IATA post pandemic traffic growth forecast, number of flights will double between 2024 and 2050 which will make a huge gap to reach Net Zero. In its “Fly Net Zero “plans, the IATA relies on SAF for 65% to ensure aviation decarbonation in 2050. With regards to forecasted capacities, that stands for an extremely ambitious objective.


Beyond all technical solutions reducing carbon emissions, a regulation of air traffic growth appears to be the ultimate adjustment variable to ensure a sustainable future for aviation.

In a recent paper, David Lee (note 5) – whose expertise on the matter is world wide recognized- is exploring the question of traffic growth with regard to different levels of SAF capacity. In a nutshell, his study says that 70% of SAF would bring the same result on carbon emission reduction that a 2,5% yearly decline of air traffic starting in 2024. Path to Net zero is most probably somewhere in between.

Again, aviation is no exception. As for any sector and business, the road to Net Zero relies on a mix of innovations and usage moderation.


Note 1: IATA Press release 66 :https://www.iata.org/en/pressroom/2021-releases/2021-10-04-03/

Note 2: IATA 20 years traffic forecast https://www.iata.org/en/publications/store/20-year-passenger-forecast/

Note 3: See paragraph of The Shift Project report (available soon in english)

Note 4: ICCT WORKING PAPER 2021 dated March 2021 (https://theicct.org/sites/default/files/publications/Sustainable-aviation-fuel-feedstock-eu-mar2021.pdf)

Note 5: David Lee: Quantifying aviation’s contribution to global warming(https://www.researchgate.net/publication/355906889_Quantifying_aviation’s_contribution_to_global_warming)


4 thoughts on “What does Net Zero mean for aviation?”

  1. Very clear post, and as said in conclusion, the pathway to net zero is probably in between technology and air traffic regulations, unless crisis like Covid or oil prices do the job!

  2. Very clear post, and as said in conclusion, the pathway to net zero is probably in between technology and air traffic regulations, unless crisis like Covid or oil prices do the job!

  3. Very clear post, and as said in conclusion, the pathway to net zero is probably in between technology and air traffic regulations, unless crisis like Covid or oil prices do the job!

  4. Very clear post, and as said in conclusion, the pathway to net zero is probably in between technology and air traffic regulations, unless crisis like Covid or oil prices do the job!

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