Bjorn’s Corner: Why e in ePlane shall stand for environment, Part 16. Bio fuels.

April 3, 2020, ©. Leeham News: In this week’s Corner, we go deeper into bio-based carbon-neutral fuels. We described the two variants of bio-based and synthetic alternative fuels last week and gave an overview of the pros and cons of synthetic fuel.

Now we dig deeper into bio-based airliner jet fuels, an already existing carbon-neutral fuel type.

Figure 1. United is using biofuel for its operations from LAX. Source: United Airlines.

Bio-based alternative fuels, a sustainable alternative

The first airliner flight with bio-based jet fuel was a Virgin Atlantic 747 flying between London and Amsterdam in 2008 with a 20% blend of biofuel to one of its engines. Today United uses biofuel in its regular operations from LAX, Figure 1.

Initially, stock from planted vegetable oil was used, but the focus has changed to stocks that do not compete with agricultural land use to produce food.

The present focus is on a sustainable chain where waste oil and other waste products are the primary sources for biofuel production.

The certification of biofuels has two dimensions:

  • To produce the fuel to a specification where it’s a true “drop-in” replacement for fossil airliner fuel. There are some issues where biofuels have gelling problems at low temperatures, and it affects earlier types of sealing materials in fuel systems. Both areas have solutions.
  • The biofuel needs certification as Sustainable Aviation Fuel (SAF) by a recognized body. Only then can authorities grant the users exemption from carbon emission schemes like the European Union Emissions Trading Scheme or ICAO’s CORSIA. The industry needs to agree on a SAF certification body and the rules for exemption from emission schemes. Without these exemptions, the biofuel alternative can’t be economically attractive to airlines and grow in usage.

The industry has successfully passed the first criteria; there are biofuels offered by companies in the US, Europe, and Asia, and several projects will increase the capacity over the next years. On the second there is work to do. Many airlines support the Roundtable on Sustainable Biomaterials (RSB) NGO as this body. It developed the first sustainable biofuel certification system.

Time to give biofuels a boost

What is needed to bring biofuels from a small scale activity in Australia (Brisbane airport) the US West coast (LAX) and Scandinavia (Oslo, Bergen and Stockholm airports) to a real alternative is government support to make the cost of biofuels the same as fossil fuels to the airlines. Only then will demand and investments in production capacity grow to where it becomes a sustainable alternative to fossil fuels.

Why is this important? Because this Corner series shows how hard it is to replace the jet fuels for air transport. Bio-based and longer-term synthetic fuels are the viable route to make air transport more environmentally friendly.

It exists today, uses the technology for jet engines and fuel systems we have perfected over the last 70 years and can create an ecosystem where our waste is recycled into fuel for the area where alternative propulsion technologies have fundamental problems.

The media hype around these almost “mission impossible” alternative propulsion systems is counterproductive to the target of reaching a sustainable air transport system.

Alternative fuels are a better route for our attention, support, and investments than the hundreds of electric and electric hybrid projects that swamp our media at present and make any coverage of alternative fuels seem low ball and unnecessary near term distractions. “Let’s focus on the more exciting electric technology, it works for cars so it should work for airliners”.

It’s the other way around. Alternative fuels are our only way together with increased airliner efficiency to make air transport more sustainable. It will take decades for this to change.

20 Comments on “Bjorn’s Corner: Why e in ePlane shall stand for environment, Part 16. Bio fuels.

    • Last year the IEA estimated that the added cost per passenger for a blend containing 15% HEFA-SPK. It was minimal, at eg roughly US$10 for a trans-Atlantic flight. See

      The IEA report refers to a relatively high cost of feedstock for HEFA, indicating HEFA is currently waste oils and animal fats. But several years ago the EU was looing at growing Camelina on land that is otherwise marginal for agriculture. Compared with Used Cooking Oil (UCO) it would be more consistent in quality and supply, and be less contaminated.

      Clearly though, even if current feedstock is considered pricey it doesn’t seem an unreasonable premium.

    • Long-term , installing conversion-plants in conjunction with waste-plants would seem straightforward . Such plants could easily produce alcohols , thus reducing gasoline and deisel burning , and helping to “green” the atmosphere , and oceans .

    • The current cost of Jet fuel is EUR 0.18/L but given the current Saudi/Russo oil glut price war say EUR 0.27/L as more realistic. UK pounds and US dollars within 8% of the EURO.

      All of the costs for carbon neutral fuels I’ve seen fall between EUR 0.70 to EUR 1.4

      EUR 0.70/L for jet fuel derived from biogas digesters using crop silage waste and manure.
      EUR 1.40/L for jet fuel derived from direct air capture of CO2 with Fischer Tropsch reaction with Hydrogen from Electrolysis using European wind power.
      EUR 1.00/L for Fischer-Tropsch using the CO2 from the above or similar biofuel fermentation process and Electrolysis from European Wind Turbine Power.
      EUR 0.85/L for Bioethanol converted to Jet fuel with 90% efficiency by ZSM5 zeolite catalyst using sugar beat. Sugar beat is one of the most efficient crops providing 2 units energy output for 1 unit input. This will be better with genetically altered energy sugar beat being developed in US and salt resistant sugar beats. There is a large amount of biogas, animal waste and CO2 that comes from the pulp and fermentation and drying for fuel.
      EUR 0.50/L for palm kernel oil which is usually the cheapest fat and comes at global cost of 0.6-0.7 U$/KG and the loss of orangutan rainforest.

      There are maybe some breakthrough in bioethanol that involve membrane filtration of the alcohol instead of the very energy intensive distillation as well as new bacterium to ferment cellulosic and ligneous materials.

      I don’t think carbon neutral jet fuel to get any lower than EUR 0.70/L. Maybe some options of production in the Australian Dessert or remote hydro or geothermal sources in say Iceland.

      Given that the best aircraft are able to operate at 2.2/Litres/100km per passenger for a 6000km transatlantic crossing we are looking at 60 x 2.2 x 0.7 = EUR92.4 fuel costs per passengers. Say EUR 135.00/passenger allowing for the fact that aircraft are not typically full.

      But at EUR 0.70/L we are still living on hope. Biofuels are limited by land availability, competition with food crops and the destruction of wilderness we are already seeing. We are limited to crop and food waste and the 30%-50% of land that must be subsidised to keep farmers on the land and guarantee food security. Fully synthetic ‘electro-fuels’ must be the destination.

      The main way we can get of this is nuclear fission power. The constancy of supply of current reactors should get the cost to EUR 0.60/L. Small modular reactors, which will be safe on a grand scale thence molten salt reactors or high temperature reactors that can split water thermochemically will bring cost down further.

      We better get cracking, the reactor engineers are getting old.

  1. Already for road fuel there are many countries that enforce % bio-fuel mix into the fuel. In the US used cooking oil is one of the major sources.
    Those mix-in ratios will increase by time.
    However there are competition for forsest waste and sorted municipal waste from Power plants often public owned.
    Imported ethanol for further processing or mix into gasoline and palm oil often runis the land they are grown on for other spieces, hence ocean and desert growing of oil plants/algea looks like the sustainable hard way forward. If IATA/ICAO agrees to certian % of biofuel globally into JET-A with a clear path forward it will boost the eco-fuel investments.

  2. Is it correct to assume that if (say) 10-20% of the aviation fuel is comprised of ‘bio fuel’ then that proportion of the CO2 emitted can be discounted from the total?
    If so clearly that is the way to go.As woody says perhaps start with an attainable goal of 10% its a huge reduction in itself – if as above it can be discounted.

    • With the current derivation of green fuels
      the “Green” has black, dirty feet.

      • True. In addition, climate fanatics won’t be satisfied with biofuels, as there is still “something” that is burning and emitting CO2.

        Carbon offsets are not good enough for the same reason.

        Climate fanatics demand essentially that the world stops burning anything.

    • Fuels derived from agricultural oils still have a input of diesel for tillage, harvest,processing and transport. Also ammonium nitrate and phosphate and other fertiliser. I suspect its only about an 80% to 85% input. I don’t think vegan animal liberationists are going to be happy to learn that animal fats are mixed in bio-jetfuel. There is a great deal of ‘waste’ material, often thrown away, that can be used and that is good. However if you cut down rainforest to grown palm kernel oil or sugar cane are you really saving CO2?

      “Green” energy and fuels scare me. They are dependant on subsidies and converting land from nature to cropping. Because they are dependant on subsidies they use political and fear based arguments to promote those subsidies.

      • Most forest land used for timber is not that well managed and the growth in these forests with professional care can triple in m^3/acre/year. Many countries does not enforce replantation after harvest and management of the plantation like keeping invasive trees at bay letting spruce and pine grow at top speed in its natural growth areas. I guess it is similar in other Forests around the World as US/Canada/Nordic/Russia are not the worst in forest management (manybe Russia). Of cause there need to be sizeable areas with virgin forests in most countries for wild Life. Even in monoculture plantations one can enforce strakes of natural mix of trees for wild animals, Hence the CO2 uptake from Forests can easily be tripled giving better timber produced with goverments interests and enforced regulations (away from the Capitals, its restaurants and lobby Groups…)

  3. Completely agree government subsidization is required to get a sustainable alternative jet fuel (SAJF) industry growing. Beyond that, there’s far more to the story.
    Today global production capacity is an incredibly miniscule fraction of the nearly 100 billion gallons of annual jet fuel use.

    Costs are extremely high.

    Six ASTM approved methods exist to make SAJFs, and none of them result in a carbon neutral fuel. It takes energy to convert plants or waste into jet fuel. These methods result in 80% or less reduction in CO2 relative to the feedstock.

    None of the approved methods can be flown “neat,” as pure biofuel. At most, they are approved as a 50% blend with Jet-A. Some are less. In the current best case we end up with a 40% (0.8*0.5) reduction in life cycle CO2 relative to straight Jet-A.

    Operating the current fleet on pure biofuel for some aircraft and engines results in fuel leaks due to elastomeric seal incompatibilities. Newer equipment can resolve this but the global fleet has a high fraction of legacy equipment that cannot.

    Approved SAJF blends are drop-in compatible with Jet-A, and all approved fuel is fungible — once it enters an airport system, there’s no way to track which airplanes get which fuel type unless there are completely separate systems for pure Jet-A and the SAJF blend, which would add huge cost and complexity.

    Some or most of the few refineries capable of producing SAJF also produce other fuels, including biodiesel. In the US biodiesel (and ethanol for gasoline) is subsidized, cost-competitive with diesel and in demand. SAJFs are not subsidized and not even close to cost competitive with Jet-A. If you own a $500M refinery, what would you produce?

    SAJF Feedstock costs are high. With no efficient transportation infrastructure in place to move feedstock to refiners and SAJF to airports, transportation costs can be very high. In contrast, oil and refinery products have extensive pipeline networks and rail access in place.

    It is not feasible to mandate airline usage of any significant amount of SAJF if there is no industry to produce it, which is the reality today with no significant financial help on the horizon to change it.

    Lastly, in a purely plant-based SAJF scenario, truly vast land areas would be needed to supply civil aviation. One could argue that since no biofuel reduces lifecycle airplane CO2 to zero, we’re better off leaving the plants in the ground where they can continue extracting CO2 for their lifetime. Others could argue that it looks pretty good from a lifecycle perspective, but all it really does is move CO2 from ground level to high altitude where it is possibly more harmful.

    As noted, this isn’t simple and it will take many $billions of investment to develop an industry that can move the needle on civil aviation’s net CO2 emissions.

    • As I mentioned in a comment in, I think, Bjorns previous post, it appears that PM may be the important pollutant to look at, rather than CO2, for aviation. The latest published report from the US National Academy of Sciences seems to show the largest % reduction on a contemporary engine being 86% for FT GTL (

      I don’t think “finanical help” is necessarily needed as clearly any globally mandated change will be supplied (assuming it is achievable). For me, the issue is how to achive a global mandate and therefore what the most appropriate pressure(s)/incentive(s) and application point(s) is.

      My gut is the 4 major engine manufacturing companies are the best place to look. If, for example, they all optimise their newest productuin for a chosen blend (but at a point where the physical disadvantage of sticking with traditional fuel is minimal at most) but the best warranties/service etc now requires use of the blend they would incentivise operators to seek the blend and a siginifcant number of champions for the fuel would emerge globally and quickly (covid-19 caveat aside and with presumably a need to mitigate for airlines operating in regions where early uptake would not be possible. Perhaps an effect similar to the switch to Ch.3 noise regs would occur).

      Regarding land usage, crop chosen is important (I mentioned the EU looking at Camelina previously for its ability to grown on land otherwise only marginally agricuturally). Plus of course we get into lots of much broader ethical & philsophical discussions about eg greening deserts, reforesting uplands, protecting rainforests that are necessary to come up with an overall plan, and the point you make about simply leaving the plants in the ground. Personally I’m not a fan of biofuel as to me it is largely kicking the can, a subsidy trough, and a publicity stunt and very little to do with genuine environment improvement.

      • Did you notice that Fischer-Tropsch fuel, apart from reducing particulates by 86% in the CFM-56, also reduced NOX by 5%-10%. Another blended fuel, RP-3 even shows a 70% reduction of NOX in a burner. Particulates and NOX are may predominantly caused by agriculture rather than modern engines. I had though that the Nordic study which advised converting biogas to jet fuel didn’t make sense in that the methane was usable in the national gas grid and one may as well simply buy Russian oil to refine into jet fuel. This shows FT fuel is vastly superior.

        • Agreed, the evidence is that ICE are not the real villain in PM. Is that agriculture PM from burning? Re road vehicles the company that developed the real world CO2 testing capability recently confirmed what many have said for years, that tyre/tire wear is vastly more PM polluting than the engines ( The study didn’t even address brake dust, which is suggested to be similarly far worse than engine emissions. Of course, for the relative effects of PM and CO2 at altitude there are no such abrasive/abraded surfaces to factor in.

          With NOX and air travel I assume the main concern is high level ozone production for its greenhouse quality, rather than lung damage etc. that is the main concern at ground level. I guess the expert decision makers on all of this will decide which of NOX, CO2, PM and anything else to focus on.

          AFAIK Direct Air Capture also uses FT to create fuel (jet included). If it can be made to work and at a reasonable cost and uses carbon neutral energy (solar etc.) to power the process then a circular energy system based on this certainly sounds an appealing one to consider. There was some progress on this announced last year (

  4. I am going to be contrary, I think in the current situation we should shift to the technical aspects of air filtration and cabin ops on aircraft as well as how long its going to be before air travel recovers to former level (5-10 year?)

    C-19 has changed the current air transport equation, oil prices are down and my well stay down for 5 years.

    Emissions are off hugely, C-19 has accomplished what Greta could not despite her valiant efforts, at a huge cost its bought environmental time.

    And that is the real situation now, where are we at now and its a different world and it may stay different.

    • I think this can be done.
      1/ A day, maybe two, before a flight a passenger will be required to obtain a certificate via a drive through test proving they’ve had a nasal and throat swab test for COVID-19 as well as a blood prick antibody test. No certificate, no boarding pass. Presence of antibodies means you are over the disease and safe and not likely to get it.

      2/ on the aircraft passengers must wear a face mask
      3/ passengers are issued with 5 antiseptic swipes and a no touch rule is enforced
      4/ antiseptic cleaning equipment is provide in bathrooms, UV lamps fitted to kill microbes when no occupied.
      5 Only hermetically sealed meals.

      Obviously a test a day prior to flying is a pretty good protection. If 5% of a population are asymptomatic carriers and the test is 95% accurate the chance of a COVID-19 carrier is less than 1/400. The hygiene measures will take care of the rest. Tests on arrival or prior to return will provide another way of tracing back contacts. We just have to get enough testing kits and facilities.

    • I don’t believe this contrail theory myself as confirmed. Nevertheless with the sky’s clear of aircraft for a month or two due to COVID 19 pandemic we should get some good data.

      The last time this happened was during 9/11 (0r 11 September for me as an Australian) when US skies were clear of aircraft for 2 days. A 1.5 degree temperature rise (not fall, lack of aviation caused cooling) was seen but this was latter attributed to just random effects.

      Call me sceptic but half the scientists in the world are now dependant on obtuse global warming connection for funding. Ten times a day some scientist, engineer, CEO or journalist invested in green power comes up with another cause.

      If we can’t release water into the air from combustion of carbon neutral hydrocarbons there are a number of alternatives.

      1 Fly more efficient aircraft.
      2 Fly lower altitude (turbo prop see above)
      3 Capture the exhaust condense the moisture in the exhaust using the low stratospheric temperature. The water, which will weigh a little more than the fuel will be pumped into an empty tank. Or convert the water into optimally size ice cubes and drop the water as ice hail that falls to lower
      altitudes or just dive to lower altitude release and climb. This might work best in turbo-compounded piston engines, closed cycle Brayton turbines or fuel cells that have stoichiometric combustion and so less volume in the exhaust.
      4 We burn carbon neutral carbon. IE we burn pure coal, no soot. Carbon can made from CO2 via the catalytic bosch reaction CO2+2H2->C + 2H2O. Already investigated as a source of carbon fibres. The German national railways ran constant volume turbines built by Halzwarth for electrical power in the 1920’s using pulverized coal. It would work as a slurry of different size particles that pack optimally.
      5 Battery electric. (low energy, and all the difficulties)
      6 Zink Air or Aluminium air batteries
      7 Hybrid, take-off and climb out using fuel, cruise on electric at high altitude. If water can be released at high altitude this would work.
      8 Burning metals such as nano aluminium and retaining the aluminium oxide, sort of an aluminium air battery but using combustion.
      9 Cryogenic hydrogen is probably the worst solution unless low altitude travel.

      Graphite and Metallic aluminium can be stored as a liquid slurry with the characteristics of a liquid fuel with a distribution of particles, for instance say 20% 40 micron particle, 80% 16 micron particle to fit in the interstices and maybe even smaller. Water could be used for carbon but oil will need to be used for the aluminium as nano aluminium reacts with water to make hydrogen.

      Closed Brayton cycle engines will work of solid fuels with abrasive content.

      • 3. The ice cubes would likely violate FAR 91.15, and collecting it as a liquid would be tricky to avoid freezing. You’d be better off adjusting altitude on humid days, that’s how the USAF solved the issue on the B-2.
        4. Carbon is less energy dense than hydrocarbons, so you’d probably hit a penalty.

        One advantage of several SAF types is that they burn cleaner and thus give off fewer condensation nuclei. On balance, the best bet is probably a mix of nothing and option 2 from your list.

  5. Comments from aviation greenies seeking to solve problems and not trumpet them. Great stuff chaps!

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