Chemical Engineer and pilot here. I’m not sure ethanol has all that much to do with SAF- it behaves terribly at even moderate altitudes and causes all sorts of issues. Ethanol can be used for gasoline replacement in spark ignition engines on the ground, but for small piston plane engines ethanol additives are expressly prohibited because they cause vapor lock and damage to fuel bladders and hoses, valves and seals not designed for it.
Jet turbines need kerosene or other middle distillates, which are much more likely to be consistent with biodiesel that comes from esterification of soybean or palm oils and that isn’t the same as the process of fermenting corn to make ethanol. Ethanol or methanol can be used as esterification agents, but that is only a small part of the overall energy density in the final fuel.
Long story short, biologically based commercial SAF has more to do with oil seeds, but we already know from biodiesel that that can’t be economic and is already a major driver of deforestation in Asia. The only SAF that could ever work would have to come from the synfuel route using DAC and Nuclear hydrogen.
While I agree that synfuel is the only plausible route (and contrary to what the author suggests in his last paragraphs, that’s a very well proven technology since Hitler-germany developed it and apartheid soutafrica optimised it over decades) i doubt that the economic route will include currently fashionable DAC and / or nuclear because both technologies are to complex for a competitive technology learning curve potential.
Thermal gasification of waste biomass (straw etc.) is a well researched process (see e.g. the plant in Güssing) including cleaning it up to synthetically natural gas (basically pure methane) and from there the Fischer-Tropsch-Synthesis (Syngas as mentioned above) is a super well proven technology to produce designer hydro carbons.
The missing links are the economics and there it comes down to three sub-areas that need better solutions:
1) investment costs could e.g. brought down by developing pressurized gasifiers that fit into ISO-containers and can be series-produced on a converted truck assembly line.
2) biomass logistics costs: require seamless tractor-/ truck-trailer solutions that make the collection from the field and on the road in a radius of up to 100km more economical. No research - just focused engineering required.
3) waste biomass costs: contrary to what one might expect, straw is about 100€/ton in Central Europe, similar to other waste biomass streams. Any ideas what could be done about this?
Burning hydrocarbons is the only (current) viable way of powering an airliner.
Widespread international travel is a possible way to avoid wars (we Brits are much less likely to war the Germans now we know them).
War is really bad for the environment.
Hence relax about decarbonising aviation focus on the low hanging fruit ... and remember there was about 36 years between the Wright Brothers and the first jet aircraft, another 10 to jet airliners.
Ethanol from corn is, as it were, a shuck! In North America it takes on average a pound of fuel to grow a pound of food. Probably a little less for corn, but basically this greenwashing maneuver is just converting diesel to ethanol. Someone should go to jail for it.
From time to time I think that the US could stabilize global food prices simply by moving the ethanol requirements. It would turn the US department of agriculture in the Federal Reserve of agricultural markets.
It is obvious, but I really think that agricultural policies shall be actively focused on price smoothing. I still cannot understand that the ethanol requirements were not relaxed at the beginning of the Ukraine war.
If we had abundant and sufficiently cheap carbon-free electricity (coughnukescough), we could set up a closed-loop system where we extract CO2 from the atmosphere (or ocean water) and make hydrocarbons out of it and water. Basically a catalytic converter in reverse.
Fantastic encapsulation of the reality we live in - the insane drive to legitimize questionable energy ouputs to appease intellectually fragile people. The effort speaks to the nature of ideologically captured capitalism - farmers willingly shafting the public by turning food into ethanol, and the chattering classes pretending that it makes and sense.
Compliments to you for making the airline scenario crystal clear. I am in agreement with your classification into three ways. This perhaps is the predicament that has failed to yield the desired results on climate change. I recall a similar attempt on biofuel (Jatropha and Pongamia) in India which made headlines initially - everyone claimed it a boon. When we look at the situation today, I find no one talking about leave alone using it.
There are two main categories of CO2 in the atmosphere. That which is part of the carbon cycle (a significant portion of which initially had been added from the burning of fossil fuels), and that which is newly added, primarily from additional burning of fossil fuels. The use of biofuels primarily reuses CO2 already present in the atmosphere; thus, giving us the opportunity to develop and use other technology to remove the too much already in the carbon cycle. Sometimes the things you might not like are the correct things to do and you reveal your bias when you don't recognize this.
I'm wondering how aviation emissions compare with emissions from coal-fired electric generation, because as long as China and India are building new coal plants, other steps to mitigate carbon emissions will remain inadequate. Meanwhile, you're right to point out the airlines' continual incentive to reduce costs and the marketing-centric "value" (read: propoganda) of today's SAF processes and performance. Wasting money pursuing ineffective strategies obscures the desired end-in-mind.
Nice examination on the merits, or lack thereof, of ethanol fuels for aircraft.
Obviously, the energy density requirements of commercial jets are currently a non-starter for batteries, but I can imagine short haul flights, perhaps akin to air taxis, being powered by electricity pretty soon.
The emissions of commercial jets is just another problem that can be solved by a carbon tax. If we “correct” the pricing “data” of fossil fuels by internalizing their negative externalities, this corrected data gets fed into the global supercomputer that we call humanity. The problem will get solved, with no need for complex rules, mandates, or regulations.
What's your take on companies like Prometheus Fuels and Terraform Industries which aim to make their fuels lifecycle-carbon-neutral by using direct air capture of CO2 in the fuel making process? Maybe there are other gotchas preventing that approach from being scalably emissions-reducing in practice, but it at least seems more straightforwardly promising than biofuels/ethanol.
Chemical Engineer and pilot here. I’m not sure ethanol has all that much to do with SAF- it behaves terribly at even moderate altitudes and causes all sorts of issues. Ethanol can be used for gasoline replacement in spark ignition engines on the ground, but for small piston plane engines ethanol additives are expressly prohibited because they cause vapor lock and damage to fuel bladders and hoses, valves and seals not designed for it.
Jet turbines need kerosene or other middle distillates, which are much more likely to be consistent with biodiesel that comes from esterification of soybean or palm oils and that isn’t the same as the process of fermenting corn to make ethanol. Ethanol or methanol can be used as esterification agents, but that is only a small part of the overall energy density in the final fuel.
Long story short, biologically based commercial SAF has more to do with oil seeds, but we already know from biodiesel that that can’t be economic and is already a major driver of deforestation in Asia. The only SAF that could ever work would have to come from the synfuel route using DAC and Nuclear hydrogen.
While I agree that synfuel is the only plausible route (and contrary to what the author suggests in his last paragraphs, that’s a very well proven technology since Hitler-germany developed it and apartheid soutafrica optimised it over decades) i doubt that the economic route will include currently fashionable DAC and / or nuclear because both technologies are to complex for a competitive technology learning curve potential.
Thermal gasification of waste biomass (straw etc.) is a well researched process (see e.g. the plant in Güssing) including cleaning it up to synthetically natural gas (basically pure methane) and from there the Fischer-Tropsch-Synthesis (Syngas as mentioned above) is a super well proven technology to produce designer hydro carbons.
The missing links are the economics and there it comes down to three sub-areas that need better solutions:
1) investment costs could e.g. brought down by developing pressurized gasifiers that fit into ISO-containers and can be series-produced on a converted truck assembly line.
2) biomass logistics costs: require seamless tractor-/ truck-trailer solutions that make the collection from the field and on the road in a radius of up to 100km more economical. No research - just focused engineering required.
3) waste biomass costs: contrary to what one might expect, straw is about 100€/ton in Central Europe, similar to other waste biomass streams. Any ideas what could be done about this?
Burning hydrocarbons is the only (current) viable way of powering an airliner.
Widespread international travel is a possible way to avoid wars (we Brits are much less likely to war the Germans now we know them).
War is really bad for the environment.
Hence relax about decarbonising aviation focus on the low hanging fruit ... and remember there was about 36 years between the Wright Brothers and the first jet aircraft, another 10 to jet airliners.
The Seafuel approach takes CO2 from ocean water and H2 from low-cost new nuclear power, shown here on substack.
https://hargraves.substack.com/p/bury-co2-or-revive-it?r=2sdto&utm_campaign=post&utm_medium=web&triedRedirect=true
CO2 is a gas of life and not a climate driver.
Ethanol from corn is, as it were, a shuck! In North America it takes on average a pound of fuel to grow a pound of food. Probably a little less for corn, but basically this greenwashing maneuver is just converting diesel to ethanol. Someone should go to jail for it.
From time to time I think that the US could stabilize global food prices simply by moving the ethanol requirements. It would turn the US department of agriculture in the Federal Reserve of agricultural markets.
We should never had had subsidies and mandates for ethanol.
It is obvious, but I really think that agricultural policies shall be actively focused on price smoothing. I still cannot understand that the ethanol requirements were not relaxed at the beginning of the Ukraine war.
If we had abundant and sufficiently cheap carbon-free electricity (coughnukescough), we could set up a closed-loop system where we extract CO2 from the atmosphere (or ocean water) and make hydrocarbons out of it and water. Basically a catalytic converter in reverse.
Rinse and repeat.
Fantastic encapsulation of the reality we live in - the insane drive to legitimize questionable energy ouputs to appease intellectually fragile people. The effort speaks to the nature of ideologically captured capitalism - farmers willingly shafting the public by turning food into ethanol, and the chattering classes pretending that it makes and sense.
Compliments to you for making the airline scenario crystal clear. I am in agreement with your classification into three ways. This perhaps is the predicament that has failed to yield the desired results on climate change. I recall a similar attempt on biofuel (Jatropha and Pongamia) in India which made headlines initially - everyone claimed it a boon. When we look at the situation today, I find no one talking about leave alone using it.
There are two main categories of CO2 in the atmosphere. That which is part of the carbon cycle (a significant portion of which initially had been added from the burning of fossil fuels), and that which is newly added, primarily from additional burning of fossil fuels. The use of biofuels primarily reuses CO2 already present in the atmosphere; thus, giving us the opportunity to develop and use other technology to remove the too much already in the carbon cycle. Sometimes the things you might not like are the correct things to do and you reveal your bias when you don't recognize this.
The bottom line is if we want to reduce net emissions of CO2, we should tax it and see how the market + technology does the job. The rest is BS.
I'm wondering how aviation emissions compare with emissions from coal-fired electric generation, because as long as China and India are building new coal plants, other steps to mitigate carbon emissions will remain inadequate. Meanwhile, you're right to point out the airlines' continual incentive to reduce costs and the marketing-centric "value" (read: propoganda) of today's SAF processes and performance. Wasting money pursuing ineffective strategies obscures the desired end-in-mind.
Robert Hargraves covers the nuclear method in his latest writings. https://hargraves.substack.com/p/serializing-new-nuclear-is-hot
Nice examination on the merits, or lack thereof, of ethanol fuels for aircraft.
Obviously, the energy density requirements of commercial jets are currently a non-starter for batteries, but I can imagine short haul flights, perhaps akin to air taxis, being powered by electricity pretty soon.
The emissions of commercial jets is just another problem that can be solved by a carbon tax. If we “correct” the pricing “data” of fossil fuels by internalizing their negative externalities, this corrected data gets fed into the global supercomputer that we call humanity. The problem will get solved, with no need for complex rules, mandates, or regulations.
An impossible dream unfortunately.
I’ll be gobsmacked if we ever see a robust global agreement on pricing carbon.
What's your take on companies like Prometheus Fuels and Terraform Industries which aim to make their fuels lifecycle-carbon-neutral by using direct air capture of CO2 in the fuel making process? Maybe there are other gotchas preventing that approach from being scalably emissions-reducing in practice, but it at least seems more straightforwardly promising than biofuels/ethanol.
That sounds far less straightforward from an energy balance point of view.