Bjorn’s Corner: Air Transport’s route to 2050. Part 1.

By Bjorn Fehrm

October 18, 2024, ©. Leeham News: In Corners over the last years, we have covered new airliner technology and engine developments that would apply to the next-generation airliners in the largest segment of the market, the single-aisle segment, or as we like to call it, the Heart of the Market segment, as it’s not sure it will be a single-aisle aircraft.

The series has assumed this generation will be hydrocarbon-fueled gas turbine-propelled airplanes. Therefore, it has not covered the current state of alternatives to gas turbine-based hydrocarbon propulsion.

We will cover this now. We are now 10 years into the discussions and work of reducing Air Transport’s reliance on hydrocarbon fuels, which started in earnest when Airbus flew the E-Fan battery-electric aircraft at the Farnborough Air Show in 2014, Figure 1.

How are we doing?

Figure 1. Airbus E-Fan at Farnborough Air Show 2014. Source: Wikipedia.

The problem

When thermal engines like a gas turbine are fueled with hydrocarbon fuel that had its CO2 absorbing phase (when it was plants) millions of years ago, and we burn it today to release the energy, we have a one-sided CO2 emission. The combustion of one kg of Jet fuel in a jet engine emits 3.2kg of CO2 (this is a one-to-one relationship; if we want to reduce the CO2 emission, we must burn less fuel or replace it).

Civil air transport has more than 25,000 airliners flying missions around the globe daily. Figure 2 shows the busiest areas.

Figure 2. Flightradar24 picture of air transport around the globe. Source: Flightradar24.

With each aircraft flying around four missions per day, we have about 100,000 flights daily (domestic aircraft flies up to seven flights a day, while long-range aircraft average two per day).

Despite air transport representing about 2-3% of the global CO2 emission problem, aviation is a very visible source of emissions (it’s loud, flying over our heads, and smells around airports).

Therefore, the industry, being high-tech and, by it, used to tackling complex problems, has expressed an ambition to get emissions under control (the latest declarations from COP26 in Glasgow don’t really stipulate any agreed-upon limits or curves) and has invested in the creation of alternative propulsion technologies to reduce or eliminate hydrocarbon fuel burn.

The industry also realizes that more than 1,000 airliners are delivered into the 25,000 every year (the majority as replacements) and that something must be done for these already existing aircraft that will live until at least 2050. The answer is to increase the blend of Sustainable Aviation Fuel (SAF), which is a fuel that is close to CO2 neutral on a life cycle basis.

Progress to date

The series is about the progress made so far, both in terms of alternative, more efficient propulsion systems and the increased use of SAF.

We will compare aviation’s progress with ground transport, a much bigger part of the problem (15% versus 3%, Figure 3), but has made further progress in changing propulsion away from hydrocarbon-fueled thermal engines.

Figure 3. Greenhouse emissions by sector. Source: Our World in Data.

We will discuss why there is progress for land transport and lack of progress in the air, what projects we see will contribute to changes in how we provide energy for air transport, and when this will affect curves like those in Figure 3.

24 Comments on “Bjorn’s Corner: Air Transport’s route to 2050. Part 1.

  1. Lots of areas were trees could grow fast and well managed are not used nor well managed. Hence the supply of cellulose for SAF and other use could increase almost 10 fold if a coordinated effort is made and as they consume CO2 and emit O2 that would lower CO2 in atmosphere. The Eastern US used to be trees from Lake Michigan to Gulf of Mexico that is mainly farmland today. Many countries sell rights to take all trees in an area for cash without requirement for replantation.

  2. Land transport hasn’t improved that much at all,there are billions of tons of batteries being driven around. The simple fact that no one seems to be focusing on is that many more lorries and vans are going to be needed to transport the same amount of goods. The UK has lifted the weight limit for a van from what was previously considered safe from 3.5 tonnes to 4.2 tonnes and these large vans still have a very poor range.
    Meanwhile,David O’Leary has threatened to “axe hundreds of routes “ if the UK government increases aviation taxes .Job done, only effective way to reduce emissions.Also improves health and provides lots of money for the NHS.What’s not to like?

  3. EV council of Australia calculates that BEVs reduce lifetime emissions by 40% on a like for like basis. Given upsizing of cars over the last 50 years I don’t think we’ve gone very far with land transport

  4. Regarding LH2 (fuel cell) aviation:

    “Airbus and Toshiba to partner on superconductivity research”

    “Over the past 10 years, Airbus has made efforts to derisk superconducting technologies. Recently, Airbus UpNext launched Cryoprop, a demonstrator to test a two megawatt-class superconducting electric propulsion system. Toshiba has been conducting research and development of superconducting technology applications for nearly half a century and has released its own two megawatt-class superconductivity motor prototype for mobility applications in June 2022.”

    https://aeronewsglobal.com/airbus-and-toshiba-to-partner-on-superconductivity-research/

    • H2 and LH2 has a role espessially if seabased windmills can go full stream all the time and produce H2 when the electrical grid cannot swallow more power. Not cheap until technology matures like 18-30 MW windmills that are designed for hard winds and pump H2 into pipelines. The other option is nuclear plants of +2000 MW for hydrogen and central heating. Not cheap either.

      • We keep getting told that large scale hydrogen production from free electricity is easy.This cannot be true or it would already be happening.
        Hundreds of millions of pounds are already spent compensating wind turbine operators for electricity that can’t be used.

        • There are a lot of cogs in motion…give it some time.

          And nothing about this problem is going to be cheap: present energy also isn’t cheap if you factor in the cost of carbon capture to clean up afterward.

          Claes is right about nuclear: regardless of cost, it’s the only non-carbon energy source that can be controlled at will “with a dial” — as opposed to wind and sun, which are subject to the whims of weather and can’t be controlled so as to match demand.

          • That’s the idea of hydrogen.If you didn’t want to store energy you would just use the electricity directly.
            As far as I am aware,no one has even demonstrated that large scale green non hydrocarbon production of hydrogen is viable using wind,nuclear or any other type of electricity

          • For nuclear you want to run the plants at constant power to aviod cycling the expensive equipment, hence the need to be able to use the power that the grid cannot swallow to produce other types of energy.

          • Nuclear reactors use control rods to regulate output: they can be inserted and removed so as to tailor production to demand.

            There’s no equivalent control mechanism for wind/solar.

        • “Hundreds of millions of pounds are already spent compensating wind turbine operators for electricity that can’t be used.”

          If thats the UK you are talking about , then its false.
          The CFD program is because the wholesale price fluctuates and when its below the ‘strike price’ they get topped up, or when its above they are supposed to pay it back.

          What a strange idea that theres ‘wind power that cant be used’ . Greenies have the strangest ideas about wind power, batteries and how planes fly

          https://commonslibrary.parliament.uk/research-briefings/cbp-9871/

          • Germany:
            Wind turbines are are cut out due to the grid lines to the south are overloaded.
            about 10..13% of available energy is dropped thus.
            Biomass installations used to be “constant power feed” but in recent years got a premium for dynamic control.
            ( investment goes with installed capacity, … )

            What the Greens want to achieves is imho driving a square peg into a much too small round hole. religion just like middle ages: pray and everything turn well.

          • That’s meant to be millions,obviously
            The number is rapidly increasing as more wind farms are being built

          • You can’t store wind or solar.

            Yea you can do pumped storage, not a lot of that.

            You can do battery banks, not cost effective or really feasible.

            You can make hydrogen with it, good luck separating them thar Coal Plant Electronics from Wind and Solar ones. No one is doing it.

  5. There is common sense that the greenhouse effect of aviation is considerably higher than calculated by the carbon dioxide emission alone. Recent studies assume a factor 3:

    https://www.sciencedirect.com/science/article/pii/S1352231020305689?via%3Dihub

    This means that aviation contributes 9% „of the problem“ and that a 100% use of SAF (which is not very likely even in 2050) can reduce the climate effect only by 33%.

    @Bjorn: Does the aviation industry take this figures into account?

    • One can apply the same emission “extension” (NOx, water vapor, soot) to ground and sea transport, home heating and industry — resulting in a restoration of the relative contribution of aviation — as part of the total picture — to a level of about 2%.

      If you include methane in the discussion — produced in vast quantities by the oil, gas and agricultural sector, and also by permafrost thawing and oceanic outgassing, the relative contribution of aviation decreases further.

      The contrail discussion has been going on for years, without a convincing consensus as to its effects.

      Whatever about SAF, use of LH2-powered fuel cells as a basis for propulsion produces absolutely no emissions whatsoever.

  6. @ Abalone:

    I do not agree. There is a difference between emissions on the ground and in the upper troposphere. The citation above is not the only one emphasizing this.

    Arguing with the “relative contribution” is not helpful either. It’s more like pointing a finger at other sectors, other nations and so on

  7. Hi Bjorn. Looking forward to this series. You’ve written in the past about fueling challenges with Hydrogen. Figured you might want to read this article as background info (particularly in light of the pods from Universal Hydrogen being no more). There are some interesting perspectives here about the trade off between tank weight for CcH2 vs the increased volumetric density CcH2 offers over LH2. Their conclusion being that CcH2 is promising for small airliners and LH2 (or sLH2) being for large airliners. Also the claimed simplicity and low cost of a CcH2 fueling station is noteworthy. As always, everybody is talking their book, so take things with a pinch of salt. You may also want to talk to Verne, a different company doing CcH2 with very serious financial backing.
    https://www.compositesworld.com/articles/cryo-compressed-hydrogen-the-best-solution-for-storage-and-refueling-stations

    • LH2@ 20,324 K is 70.9kg/m³
      GH2@ 273 K is 0,0899 kg/m³

      i.e. you need to compress GH2 to 788 bar for the same specific volumetric weight.
      pressure vessels with proven burstlimit of 1500Bar are supposed to be lighter than some thermal isolation tankage?

      • Hi Uwe. You should read the article. Cryo Compressed H2, CcH2, is not the same as Compressed ambient temperature H2, GH2. CcH2 is typically compressed in the 300-400bar range and has a higher volumetric density than LH2. Here’s a very simplified explanation by Verne: https://www.verneh2.com/solution
        (I think Verne’s first implementation in some heavy duty trucks in Canada is at 30MPa)
        The first article I linked has Cryomotive suggesting that the trade offs favor CcH2 for smaller airliners and LH2 for larger airliners. CcH2 tank is heavier than LH2 tank, but lighter than 700bar tank. Some trade offs are losses in the transfer of H2 (favors CcH2, bigger LH2 tank = fewer losses vs smaller LH2 tank), fueling speed & simplicity (favors CcH2), and volumetric density vs gravimetric density (depends on tank diameter). Final solutions still TBD, but an interesting debate to be aware of imho.

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