Bergen successfully runs engine on low H2 blend with no hardware changes
EV Metals Group signs FEED Agreement for development of lithium chemicals plant in Saudi Arabia

ICCT study finds LH2-powered combustion aircraft can play an important role in meeting aviations 2050 climate goals

A new study from the International Council on Clean Transportation (ICCT) has found that although liquid-hydrogen- (LH2)-combustion aircraft do not perform as well as their jet fuel counterparts, they can still play an important role in meeting aviation’s 2050 climate goals.

The study explores the potential performance characteristics, fuel-related costs and emissions, and replaceable fossil fuel market of LH2-powered aircraft entering service in 2035. Only evolutionary advances in design parameters that are feasible by 2035 were considered.


CO2e emissions from passenger aviation under various scenarios of adoption of LH2- powered aircraft, 2020 to 2050. Mukhopadhaya and Rutherford (2022)

The study explores two LH2 combustion designs:

  • a smaller turboprop aircraft targeting the regional market; and
  • a narrow-body turbofan aircraft suitable for short and medium-haul flights.

These designs are benchmarked against the ATR 72 and the Airbus A320neo, respectively. Both designs require an elongated fuselage to accommodate LH2 storage behind the passenger cabin.


Representation of the tank and passenger cabin layout for the LH2-powered narrow-body. Mukhopadhaya and Rutherford (2022)

The study found that compared to fossil-fuel aircraft, LH2-powered aircraft will be heavier, with an increased maximum takeoff mass (MTOM), and less efficient, with a higher energy requirement per revenue-passenger-kilometer (MJ/RPK). They will also have a shorter range than fossil-fuel aircraft. Nevertheless, the authors estimated that evolutionary LH2-powered narrow-body aircraft could transport 165 passengers up to 3,400 km and LH2-powered turboprop aircraft could transport 70 passengers up to 1,400 km. Together, they could service about one-third (31 to 38%) of all passenger aviation traffic, as measured by revenue passenger kilometers (RPKs).

Fueling LH2 designs with green hydrogen is expected to cost more than fossil jet fuel but less than using blue hydrogen and e-kerosene. While the market for LH2 aircraft could be broad, powering it with green LH2 will increase fuel costs compared to conventional Jet A aircraft. Carbon pricing would be needed to make green LH2 cost-competitive, the authors said, with breakeven compared to Jet A expected at between $102 and $277/tonne CO2e in 2050, depending on geography.

However, given the industry-wide push toward non-biomass SAFs, synthetic fuels like e-kerosene would likely be a better cost comparison for hydrogen than Jet A, especially from 2035 onwards.

The ICCT results suggest that green LH2 will be cheaper than e-kerosene on routes up to 3,400 kilometers.

Under the most optimistic fuel and fleet turnover assumptions, evolutionary LH2-powered aircraft could cap, but not absolutely reduce, aviation CO2 compared to 2035 levels, the authors found. This would require all replaceable missions in 2050 to be serviced by LH2-powered aircraft using green hydrogen and would result in mitigation of 628 Mt-CO2­e in 2050, representing 31% of passenger aviation’s CO2e emissions.

ICCT modeling suggests that a 20% to 40% adoption rate is realistically achievable and would mitigate 126 to 251 Mt-CO2e in 2050, representing 6% to 12% of passenger aviation’s CO2e emissions. Other technologies, including more fuel-efficient aircraft and sustainable aviation fuels, along with measures to moderate traffic growth will be needed to meet airlines’ aggressive climate goals of net-zero emissions by 2050.

Even after considering the performance penalties for carrying LH2 as a fuel source, the aircraft modeled in this work can capture a large section of the aviation market. They can provide significant reductions in carbon emissions of the captured market but can, at a maximum, cap global passenger aviation emissions at 2035 levels. The aircraft can fit into existing airline route operations but will require significant investment in infrastructure to make them viable.

—Mukhopadhaya and Rutherford (2022)




will be heavier
but less than using blue hydrogen
I disagree


I would believe battery electric for regional and short to medium haul aircraft before I would believe liquid H2. The reason is pure economics. Bye Aerospace is projecting that their 8 passenger turbo-prop replacement replacement plane will have a seat mile cost 1/4 that or the the equivalent turbo-prop and meanwhile the projected cost of LH2 in considerably more than the equivalent jet fuel powered turbo-prop. Bye Aerospace is projecting a 500 nm or 925 lm range with IFR reserve and this is with current batteries with ~260 Whr/kg. Eviation Alice is an 11 place plane that will probably be flight testing in the next few weeks. They are projecting an 800 km range. I believe that lithium sulfur batteries with at least 3 time the energy density and a lower cost will be commercially available sometime between 2025 and 2028. Liquid hydrogen is not going to hack it for short or medium haul flight and I would believe some type of "sustainable aircraft fuel" will be preferred for long-haul flight.

Nick Lyons

Consider the infrastructure challenges of storing and distributing LH2 compared with synthetic kerosene, which can use existing infrastructure. Consider the need to build a fleet of completely new aircraft types compared with the ability to drop synthetic kerosene into existing aircraft.

This is a silly idea.


Why no Ammonia fuel option in the study? It might be a cheaper and less energy intensive. On board aircraft Ammonia fuel storage is so much easier than LH2!

Roger Pham

This study is completely flawed, and is based on the assumption that the LH2 fuel and storage system offer no weight saving over that of petroleum fuel. In reality, LH2 fuel weighs but 1/3 that of petroleum fuel per kWh of energy. The use of polyurethane insulation foam with thickness of 4 cm only adds around 2% weight gain over the weight of LH2, while the airplane's skin and bulkhead structure outside of the insulation foam remains the same. Of course, we would need an internal layer of thin aluminum inner lining of the fuel tank for sealing tightness, and this would add perhaps under 1% weight gain. So, to store 1000 kg of LH2, we would need around 20 kg of insulation foam and 10 kg of thin aluminum inner lining for this polyurethane fuel tank. A medium transport airliner holding 50,000 kg of kerosene fuel would need to hold only 17,000 kg of LH2.

This massive weight saving would permit major weight saving in wing and tail, landing gear, engine, etc...and would result in gross take-off weight of around 55-60% that of the equivalent kerosene-burning version, which, in turn would further decrease the size and weight of the LH2 tank.

Furthermore, instead of lengthening the fuselage, the fuselage could be made wider for more seats per row, to compensate for the rear section holding the fuel tank, thus reducing the gain in skin surface area and hence drag.

Roger Pham

So, leṭ's say that the LH volume will increase fuselage volume by 25%. If we lengthen the fuselage by 25%, then we will increase fuselage skin drag by 25%.
However, if we would increase the fuselage diameter by only 11%, we would be able to achieve a gain in internal volume by 25%, yet will only have a gain in skin surface area of 11%. I wonder why the ICCT didn't consider this trick to increase internal volume while having the least increase in skin surface drag and weight gain.

So, it appears that the ICCT has no intention to show the LH2 fuel in the best possible light.


LH2 takes twice the volume but half the weight


@ Roger Pham and SJC

The density of liquid hydrogen is 70.85 g/L (at 20 K), a relative density of just 0.07. The density of JetA is about 800 g/L. Hydrogen has about 3 times the specific energy of JetA but takes about 4 times the volume for the same energy. Take a look at the space shuttle. That huge orange tank was just to carry the liquid hydrogen. Also, note that the diagram of the aircraft in the article above would not work as the CG would move forward as the fuel was burned. This is why aircraft fuel is typically carried in the wings.


Ammonia is more energy expensive than hydrogen because you first need to make the hydrogen and then you need to add more energy to create the ammonia. Liquid ammonia is more energy dense than plain liquid hydrogen on volume basis.

Anyway, I firmly believe that economic drivers will prevent the use of either liquid hydrogen or ammonia from being used as an aircraft fuel anytime soon.

Roger Pham

Even though LH2 has 4 times the volume as Kerosene per unit of energy, the sheer lightness of LH2 would means that only a little more than half of the fuel energy would be required to carry the same payload as when kerosene fuel is used. This means that only over twice the fuel volume of that of Kerosene would be required for LH2 fuel.
Actually, placing the LH2 tank in the rear of the aircraft is very advantageous from the standpoint of safety, because in a survivable crash impact-wise, the rear of the aircraft would always be intact and spared of engulfing fire as would happen when the fuel is stored in the wings. The nose-heavy condition of the aircraft at landing would be of no problem, but in fact, would contribute to increase safety against unintentional stall or spin.


The space shuttle was a lot of weight straight up at high velocity


@Roger Pham

Did you read the above article:

"The study found that compared to fossil-fuel aircraft, LH2-powered aircraft will be heavier, with an increased maximum takeoff mass (MTOM), and less efficient, with a higher energy requirement per revenue-passenger-kilometer (MJ/RPK). They will also have a shorter range than fossil-fuel aircraft. "

Also, I assume that you are neither a pilot or a aircraft designer. There is a fairly small window for the CG. If the CG changes too much the aircraft will become unstable and the elevator will not be able to overcome the pitching tendency.


The article is wrong

Robert McLachlan

@sd: Eviation Alice will be lucky to get a useable 360 km IFR range, not 800 km. Bye Aerospace do not even have a 2-seater yet nor a motor for their planned 6-seater. There is a blizzard of hype and investment around electric planes but no actual passenger planes yet. More analysis at


they make erroneous assumptions on the cost of blue hydrogen and the weight of LH2


@Robert McLachlan

I will absolutely agree that there is a lot of hype -- part of the "fake it until you make it" culture. I also think that a number of the pioneers and especially the eVTOL pioneers will end bankrupt and some of them have much more of "other people's money" than they deserve and that will go down the drain. However, Bye does has had their 2-seater flying since 2020 but it is not yet certified. Pipistrel does have a 2-seat electric plane flying that is certified in Europe but it is not yet certified in the US. Eviation was supposed to have their initial flight in 2021 but they are late. However, it was undergoing taxi testing 2 weeks ago so hopefully it will be flying soon. Will have to see if they make it. Anyway, if no one tried, it would never happened.


I think that the authors of the article know the density of LH2. The problem is not the density of LH2, it is the weight of the tankage to keep it liquified. With space craft such as the Shuttle, the hydrogen only needed to stay liquid for about 5 minutes. The tank was continuously being topped off until about 30 seconds before launch. Also the so called "blue hydrogen" is mostly a big oil scam.

Roger Pham

The ICCT study is faulty. NASA has done research on the use of polyurethane foam as insulation for LH2...Please look it up. Polyurethane foam is extremely light and has high R value. The fuel tank of the Space Shuttle has the fuel fraction weight of 80%, because of the shell of the tank which must hold pressure of at least 1 ATM. The plane has the fuselage to hold pressure, so there is no need for the tough shell, and the fuel fraction weight can be as high as 97% when the shell of the plane's fuselage is discounted from the fuel storage system.

You have no knowledge of aerodynamics. Jetliners do NOT have elevator to control the pitch, but the WHOLE horizontal tail plane pitches up and down to control the pitch, thus having very high pitch control authority. Furthermore, the tail plane can be made bigger, much bigger if necessary, to provide lift to the tail section during the early phase of the flight when the tail section is heavier, and the tail plane will be carrying less and less lift when the tail will becoming lighter when the fuel will be consumed.


@Roger Pham

I looked up your article which I assume is "Cryogenic foam insulation for LH2 fueled subsonic transports" Main article is behind a paywall but it is mostly about testing thermal cycling with different foams. Nothing about R values or weight. Anyway, I think that you need at least a double walled vacuum container for holding liquid hydrogen for any length of time more than a few minutes. This is based on nothing more than having vacuum drinking containers for holding hot or cold drinks which have no where near the temperature difference of ambient air and LH2.

Most if not all jet airliners if not have all separate elevators and horizontal stabilizers including all of the past and current Boeing and Airbus Aircraft and all of the US jet cargo aircraft. Many of the newer aircraft move the horizontal stabilizer for pitch trim but they still have separate elevators. Military fighter aircraft have all flying elevators (but they are still elevators) which is required for supersonic flight. Maybe you can find an example of a commercial jetliner with an all flying tail. Also, I am currently building an STOL aircraft with flaperons, slats, horizontal stabilizers and elevators with a separate trim flap, and an all flying rudder without a vertical stabilizer. Yes, you could build an aircraft that could handle a varying CG. However, it would not be the most efficient design. But you are right, I am stupid and do not know anything about aerodynamics or heat transfer.


Was supposed to read "Most if not all jet airliners have separate elevators and horizontal stabilizers ..." but I hit control C instead of Control X. Maye a better explanation is that the trim is used for slow pitch adjustment while the elevator is used faster pitch changes. The reason that all flying elevators are used for supersonic flight has to do with the shock wave that is generated in supersonic flight. Look at for an example of a typical shorter haul jet aircraft that is somewhat like what the article is focused on. Note that this plane has elevators with separate trim tabs or surfaces and does not use a moving horizontal stabilizer for trim. However some older small planes such a the J-3 Piper Cub had a moving horizontal stabilizer for pitch trim.

But Roger, you are still correct, I am stupid and do not know anything about aerodynamics or heat transfer.

Roger Pham

Hi sd,
Well, you're right about jet airliners have all-moving horizontal stabilizer for pitch trim, and elevators for faster instantaneous pitch control with lower authority. I was wrong about that detail. We are all here to learn, so who know what and how much is not as important as continual discussion to find the truth.

Regarding the insulation of cryogenic liquids, there is usually a vacuum layer to greatly reduce heat transfer. With LH2, there is one unusual point, and that is since it is so cold, well below the freezing point of air, and the polyurethane foam is a closed-cell foam structure, then the layers of foam cells near the LH2 will have the air liquefy and frozen in effect creating a vacuum there. So, the foam simply need be strong enough to withstand 1 ATM of pressure with some safe margin, while the vacuum will be created automatically as the LH2 tank will be filled up.
Please rest assured that NASA has thoroughly investigated the use of light foam for LH2 insulation many decades ago.



I did not think about the air in the foam freezing as the freezing point of nitrogen and oxygen is above the boiling point of hydrogen. However, the hydrogen is still going to boil off at a fairly high rate. Liquid hydrogen has been used for upper stages of rockets as the weight is rally important and the hydrogen only needs to be stored for a few minutes. NASA was apparently looking at the possibility of using it for supersonic transport but maybe the rate that it is being used would not be higher than the boil off rate. Anyway, hydrogen, in general, has cost and containment problems and liquid hydrogen makes the problems even worse. I do not expect to see hydrogen powered aircraft in my lifetime but maybe I would be considered old so maybe I should say anytime in the next 3 decades or more. I do expect to see some battery powered aircraft in general usage for commuter or short to medium haul flights before 2030. If they can hit their projected seat-mile cost, there will be a tipping point just as there appears to be a tipping point for electric vehicles. I am less optimistic about the wide scale use of eVTOL air taxi aircraft but there sure is a lot of hype so maybe I am wrong. However, in general, I am a strong believer in economics as a driver. Anyway, time will tell and maybe we will eventually have cheap clean hydrogen.

The comments to this entry are closed.