If you use sequestered fossil carbon and agricultural waste bio-carbon along with good renewable hydrogen made of wind and solar electricity in tubular SOECs, we can make plenty of SAF

@Davemart
You are correct Direct Air Capture probably will not be economic unless there is some extraordinary breakthrough, if ever.
You also said in a recent post on the 2023 DOE Billion Ton Report about sustainable biomass:
“ At my age my memory horizon stretches back to what I had for breakfast, if I am lucky, not discussions from 10 years ago!”
What about your memory from two weeks ago (3/4/24)?
In the Hamburg University of Technology (TUHH) has compared the Fischer-Tropsch (FT) and methanol pathways for the production of Sustainable Aviation Fuels (SAF) derived from renewable energy sources.
You made some very good comments about research from the University of California Riverside on Co-solvent Enhanced Lignocellulosic Fractionation pretreatment process, or CELF:
“Using poplar in a CELF biorefinery, the researchers demonstrate that sustainable aviation fuel could be made at a break-even price as low as $3.15 per gallon of gasoline equivalent. The current average cost for a gallon of jet fuel in the U.S. is $5.96.”
Here are some more references on this subject:
https://news.ucr.edu/articles/2024/02/07/inexpensive-carbon-neutral-biofuels-are-finally-possible
https://www.nrel.gov/news/program/2024/biorefinery-model-points-to-a-better-method-at-producing-co-products.html
There were also good comments about Coppicing, however one in particular was not completely accurate:
“ The merits of Native Coppice Forestry are widely known in Europe but apparently not in the USA - perhaps having been lost during colonisation. ”
Coppicing and Pollarding are widely used in North America and other parts of the world. It is also called Permaculture and is important for Forest Management and reducing forest fires.

Gryf:

My figure attests that I have my breakfast more often than once every two weeks!

Here is the discussion we are talking about:
' https://www.greencarcongress.com/2024/03/20240304-tuhh.html'

As I note there, using lignin for biofuels is potentially at least, way more efficient and perhaps available in the right quantities.

But the key word is potentially, as this is really early stage stuff, and for folk like me who can really only manage to do a bit of accountancy based on fairly established figures from the technologies the scientists and engineers have established, there is more or less nothing to grab hold of, nothing to evaluate.

But the aero industry is wishing to go full steam ahead with producing more and more planes, including the long range ones putting out most of the GHG, without any substantial, developed, let alone costed plans in place to mitigate, let alone reduce, their emissions.

Aircraft do not even pay equivalent tax, let alone any loading for GHG.

This for an industy which is in no way critical for the functioning of the economy, unlike for instance other high GHG emitters, which include the power supply industry, steel, concrete and glass, all of which have far more credible plans in place to reduce emissions,

The aircraft industry is AFAIK unique in reckoning that it is OK to vastly increase its emissions, with no more than a pious hope in place to reduce them, sometime, and certainly not now.

You think that hydrogen for aircraft won't work, and obviously have incomparably more expertise than members of the public like me to substantiate that view.

Airbus and others would disagree, but they are a very long way from proving their point, and in any case we are decades away from that being relevant to the main GHG emitters, long range aircraft, so any debate about that is irrelevant for the foreseeable future in the context of GHG emissions.

So what gets my goat is the aircraft industry's notion that increasing their emissions without any credible plan in place to contain, let alone reduce, GHG emissions, is acceptable.

Flying to Majorca for a holiday, or Davros for the movers and shakers, is not a necessity.

Containing, not expanding, GHG emissions, is.

SAF from lignin is a wonderful potential resource.

It is a bloody awful excuse for expanding the airfleet on the assumption that it, or
'Something will turn up'.

“ But the key word is potentially, as this is really early stage stuff,”
Potentially, until Biorefineries are built. The research is at least 10 years old.
https://www.bio.org/sites/default/files/legacy/bioorg/docs/Charles%20Wyman_0.pdf

Research is fine, I am all in favour of it.
That is not anything like substantial costed, proven technology to produce SAF with low emissions.
Moving the global container shipping fleet to nuclear is a lot closer to being a proven technology than decarbonising long distance flight, as there are plenty of large ships powered by nuclear reactors.
I would not bet on it though, or invest money in it.

“ Moving the global container shipping fleet to nuclear is a lot closer to being a proven technology”.
Nothing new there either. The NS Savannah was launched in 1959. Good concept, just not cost effective for commercial shipping.
Nuclear powered submarines and Aircraft carriers, with the exception of the French are fueled with Highly Enriched Uranium (bomb grade stuff) and are very expensive.

@Gryf quoted and commented:

' “ in total disregard of any substantial, proven, let alone costed means to contain, let alone reduce GHG emissions.”

What does that mean?'

If I have missed substantive, costed plans to contain or reduce GHG emissions from flying long range, please give me links.

I am aware of plans to increase the aircraft fleet, and to produce some nominal amounts of SAF, at a maximum of 50% of the kerosene content, but little else.

“I am aware of plans to increase the aircraft fleet, and to produce some nominal amounts of SAF, at a maximum of 50% of the kerosene content, but little else.”
That is for today. SAF is still expensive with current technology.
Of course, how many air aft are flying with Hydrogen?

Gryf:

I have no wish for an adversarial discussion, and I enjoy interacting with you.

But I do not follow your argument.

At no stage have I said or claimed that hydrogen is remotely ready to power long distance transatlantic flight. Nor have Airbus indicated any such plans.

However, they have indicated that they are looking at liquid hydrogen for aircraft, which would plainly allow at some stage longer distances than gaseous, which you appear to rule out.

I have no idea why you repeatedly contrast SAF to hydrogen, as at no stage have I claimed that hydrogen is ready to replace SAF.

Why you should refer to something going wrong with the use of hydrogen in a Shuttle in 1986 is just as confusing.

How many sucessful flights were there in 1986 using SAF?

I have simply argued that SAF is currently not really in the works to substantially reduce GHG, which has nothing at all to do with how hydrogen is doing, so why you seek repeatedly to confound the two is not clear.

I repeat, there is no obligation for critics of what is being realistically planned for SAF to have an alternative such as hydrogen ready to power the vast expansion aircraft manufacturers want and project.

We can simply fly less, without causing the world economy to grind to a halt.

Gryf

I give up.

It does not matter how many times I say that hydrogen is not a present competitor to SAF you simply do not listen.

'Aircraft travel is a small contributor to GHG. Less than 4% and 80% of that is on long flights'

Yeah, projected to rise massively by 2050 as they are ploughing right ahead producing more aircraft whilst paying lipservice to decarbonisation with 50% SAF at some unspecified time by unspecified means at unspecified cost the cover story.

No point in saying again that the alternative I support is to fly less, such as France's measure to stop short flights, I suppose, as you will simply claim that pm some obscure way I am claiming that hydrogen is the competitor for flights I don't think should happen.

Gryf sought to argue:

' “Why you should refer to something going wrong with the use of hydrogen in a Shuttle in 1986 is just as confusing.” This is part of Hydrogen fuel tank research which you brought up, i.e. GTL'

Wow. So you want to argue that the state of the tech in 1986 is relevant to what we can do today?

Bang go electric cars then, as they might have been a touch impractical using 1986 tech,

GTL if building demo dewar tanks for hydrogen right now, using present tech, not that of 1986

No point in saying again that that is wholly irrelevant to what will happen in long distance air transport for the next 25 years though, as that will be ignored.