Article on sustainable aviation fuels for airlines

Cap'n Jack

Cap'n Jack

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Cap'n Jack
Link: https://cen.acs.org/energy/biofuels/Flying-low-carbon-skies-sustainable/100/i21

The article discusses the 4 ASTM approved routes for producing green jet fuel. They are alcohol to jet, hydrotreated esters and fatty acids, catalytic hydrothermolysis, and the Fisher-Tropsch they you may remember from your chem 101 classes.

Most flights with green jet fuel run up to 50% renewable- this is a reason why:
Like all fossil fuels, jet fuel also contains small aromatic molecules. Aromatics cause swelling in rubber and plastic gaskets, O-rings, and hoses in airplanes, so those parts are sized and engineered accordingly. Take the aromatics away, and the parts shrink and start leaking. Because most routes to SAF don’t make aromatics, for now, airplanes are allowed to fly on no more than 50% SAF.
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I'm sure the usual people will chime in and explain why it won't/can't work. :)
 
Cap'n Jack said:
Most flights with green jet fuel run up to 50% renewable-
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FYI: there have been some revenue flights that run 100% SAF in one engine right now. Plus there are several aircraft to include helicopters testing completely on 100% SAF. Regardless what the naysayers may comment, its this path that will be the spot-gap between JET-A and true E-aircraft using existing airframes and engines. Throw SAF micro turbines into the mix and I think you see a whole new breed of proplusion for smaller aircraft which battery powered versions cant compete with. Interesting times ahead.;)
 
I would question the current economics too, but not the future economics. There are things about the future that we don’t know and the cost or benefits might be completely off the charts at that time. Social, environmental, political, health, etc. I know, I’m being a bit academic.
 
I just don’t have time for this green devolution in my life right now, I mean want me to pay even more for gas? Get out of here lol
 
455 Bravo Uniform said:
I would question the current economics too, but not the future economics. There are things about the future that we don’t know and the cost or benefits might be completely off the charts at that time. Social, environmental, political, health, etc. I know, I’m being a bit academic.
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The only reason I see for sustainable fuels is as a hedge against running out of conventional fuel. Ain't like it creates any less CO2 when burned...

What angle am I missing?
 
I have been running a 99% renewable diesel in my truck for over 3 years. It is pretty widely available in the LA/Orange County area starting several months ago. It is not biodiesel, it is fully refined in a very similar way as fossil diesel. There was some initial concern about lubricity of the renewable vs. fossil diesel, but there are additives in the renewable fuel to address this and I have not read about it being an issue. I suspect they can similarly engineer the additives for jet fuel.

The renewables are sourced mostly from vegetable oils. There is concern about where the palm oil components are sourced and whether that is being harvested appropriately. From what I have read, the renewable diesel nets about half the CO2 footprint of a fossil fuel diesel, which sounds like a reasonable estimate when all factors are considered.

For me a primary benefit has been extremely clean exhaust, and I use about half the amount of DEF running renewable vs. fossil diesel. This will likely result in fewer possible issues with the complex exhaust filtering/treatment system.
 
kyleb said:
The only reason I see for sustainable fuels is as a hedge against running out of conventional fuel. Ain't like it creates any less CO2 when burned...

What angle am I missing?
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I was coming at it completely from a production standpoint, having made a career in the petrochem industry.
 
As far as renewable diesels aka vegetable oils I have a friend that has an old 7.3 Powerstroke that’s setup to run it…I don’t think he can start on it…but smells like French Fry’s rolled down the road if your following…sort of a prepper thing…
 
Bell206 said:
FYI: there have been some revenue flights that run 100% SAF in one engine right now. Plus there are several aircraft to include helicopters testing completely on 100% SAF. Regardless what the naysayers may comment, its this path that will be the spot-gap between JET-A and true E-aircraft using existing airframes and engines. Throw SAF micro turbines into the mix and I think you see a whole new breed of proplusion for smaller aircraft which battery powered versions cant compete with. Interesting times ahead.;)
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Why test with only one engine, unless it is a single engine plane? I wonder if they are testing the seals and other stuff under real conditions?

fasteddie said:
I have no doubt the science behind the production of the fuel is sound.

I question the economics of it all.
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See below...
455 Bravo Uniform said:
I would question the current economics too, but not the future economics. There are things about the future that we don’t know and the cost or benefits might be completely off the charts at that time. Social, environmental, political, health, etc. I know, I’m being a bit academic.
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I question whether there is enough feedstock, but the people producing the stuff are making a profit. The article mentions contracts out 20 years or so. Some of the firms are finding more profit make diesel fuel rather than SAF

kyleb said:
The only reason I see for sustainable fuels is as a hedge against running out of conventional fuel. Ain't like it creates any less CO2 when burned...

What angle am I missing?
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Made from stuff that took CO2 from the air such as cooking oil, or residue from paper making or other wood. It becomes closer to a closed cycle.

Jeff Oslick said:
I have been running a 99% renewable diesel in my truck for over 3 years. It is pretty widely available in the LA/Orange County area starting several months ago. It is not biodiesel, it is fully refined in a very similar way as fossil diesel. There was some initial concern about lubricity of the renewable vs. fossil diesel, but there are additives in the renewable fuel to address this and I have not read about it being an issue. I suspect they can similarly engineer the additives for jet fuel.

The renewables are sourced mostly from vegetable oils. There is concern about where the palm oil components are sourced and whether that is being harvested appropriately. From what I have read, the renewable diesel nets about half the CO2 footprint of a fossil fuel diesel, which sounds like a reasonable estimate when all factors are considered.

For me a primary benefit has been extremely clean exhaust, and I use about half the amount of DEF running renewable vs. fossil diesel. This will likely result in fewer possible issues with the complex exhaust filtering/treatment system.
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Refined in a way similar to fossil fuel? Since saw vegetable oils in your post, I'm guessing it is the catalytic hydrothermolysis process which has a biocrude intermediate.
 
Cap'n Jack said:
Why test with only one engine, unless it is a single engine plane? I wonder if they are testing the seals and other stuff under real conditions?
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They've already performed the compatibility tests. The single engine 100% SAF tests (on multi-engine) are part of the 100% certification tests in real-world conditions. United flew a 737 MAX 8 with one engine 100% and I believe there was a A380 that flew a long range revenue flight with one engine on 100% plus a number of other aircraft working through the process.
MauleSkinner said:
Conventional fuels will be ended politically before we run out.
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This and the end of "easy" oil is growing nearer. Nothing "renewable" compares to fossil-based fuels on a number of levels. But current battery-technology pails in comparison to the SAF route as well. From what I've seen SAF propulsion technology will go hand-in-hand with conventional fuels and equipment until there is a major break though in E-tech or some other form of fuel like hydrogen which is also being worked. At least on the aviation side.
 
Jeff Oslick said:
I have been running a 99% renewable diesel in my truck for over 3 years. It is pretty widely available in the LA/Orange County area starting several months ago. It is not biodiesel, it is fully refined in a very similar way as fossil diesel. There was some initial concern about lubricity of the renewable vs. fossil diesel, but there are additives in the renewable fuel to address this and I have not read about it being an issue. I suspect they can similarly engineer the additives for jet fuel.

The renewables are sourced mostly from vegetable oils. There is concern about where the palm oil components are sourced and whether that is being harvested appropriately. From what I have read, the renewable diesel nets about half the CO2 footprint of a fossil fuel diesel, which sounds like a reasonable estimate when all factors are considered.

For me a primary benefit has been extremely clean exhaust, and I use about half the amount of DEF running renewable vs. fossil diesel. This will likely result in fewer possible issues with the complex exhaust filtering/treatment system.
Click to expand...
Imagine filling 33k gallons for a 787. That’s a lot of fat greasy Americans
 
Bell206 said:
They've already performed the compatibility tests. The single engine 100% SAF tests (on multi-engine) are part of the 100% certification tests in real-world conditions. United flew a 737 MAX 8 with one engine 100% and I believe there was a A380 that flew a long range revenue flight with one engine on 100% plus a number of other aircraft working through the process.
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No argument with your information, but that still doesn't answer why only one engine is was being flown with SAF.
 
Cap'n Jack said:
but that still doesn't answer why only one engine is was being flown with SAF.
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Safety. 100% SAF hasn't reached full certification yet. The compromise to further study its use on revenue flights was 100% SAF in one engine and 100% JetA in the other engine. However, since then there are test flights going on in the EU where 100% SAF is being used for both engines. I believe the current unrestricted SAF certification is a 50/50 mix of SAF/Jet A. There are also several turbine helicopters finishing up 100% SAF trials which from what I've read may lead to the beginning of 100% SAF final certification. But I haven't been in a position to see any results or info for 2023 yet.
 
MauleSkinner said:
Conventional fuels will be ended politically before we run out.
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Not to change it to political, but I think that's only going to be true here and in western europe. I don't see overall use of fossil fuels going down, it's just that first world countries will be keeping the cost of ff low because they'll be burning corn. The rest of the world will continue to increase their use of ff. I could be all wet.
 
Let’s use more expensive fuels now because if we don’t, the cheap fuel will eventually become expensive. Make perfect sense to me.
 
I recall a number of years ago on an international trip that the only English TV was CNN International. This one reporter did a week long series on how great Brazil was as they run on 85% to 100% ethanol. They actually import oil, refine it, and export gasoline.

He was out in a sugar cane field talking about how great they are because of all these fields of sugar cane were being used for car fuel versus fossils fuels.

It would have been a lot more impressive, if this same reporter a couple of months before had not done a multi part piece about how horrible it was the rain forest was being destroyed for crops. IN BRAZIL. For those fields of sugar cane.

Even in the US, the use of corn to make ethanol has driven up the price of corn, so that aid groups can't buy as much corn to ship to starving countries.
 
Pinecone said:
Even in the US, the use of corn to make ethanol has driven up the price of corn, so that aid groups can't buy as much corn to ship to starving countries.
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Have a citation for that? They do more with the corn that simply ferment it. The distiller's grain is used for animal feed rather than the corn itself. They also remove the oil, too.
 
Cap'n Jack said:
Have a citation for that? They do more with the corn that simply ferment it. The distiller's grain is used for animal feed rather than the corn itself. They also remove the oil, too.
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There were a couple of articles a number of years ago about the lower weight of grain that the aid organizations could afforf.

My favorite was an site supporting the use of ethanol in auto fuel that included a letter from Secretary of Agricultural stating that the price of ethanol would not go above $1.50 a gallon even when its use in auto fuel. At the time I found the site, ethanol was $3.50 a gallon. OOOPS.

And let's not forget to look at the overall energy cost per gallon of ethanol, including planting, irrigating, harvesting, transporting, processing
 
Pinecone said:
There were a couple of articles a number of years ago about the lower weight of grain that the aid organizations could afforf.

My favorite was an site supporting the use of ethanol in auto fuel that included a letter from Secretary of Agricultural stating that the price of ethanol would not go above $1.50 a gallon even when its use in auto fuel. At the time I found the site, ethanol was $3.50 a gallon. OOOPS.

And let's not forget to look at the overall energy cost per gallon of ethanol, including planting, irrigating, harvesting, transporting, processing
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Oh...a couple of articles! That's a great citation! I'll make sure I use that style in my next journal article!:rolleyes:
And then you post more unsubstantiated claims. :rolleyes:
 
The proof is left to the student.

The data is out there.

I cite a couple of articles as that is how many I read. I did not look for or read any more
 
Pinecone said:
The proof is left to the student.

The data is out there.

I cite a couple of articles as that is how many I read. I did not look for or read any more
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Proof is left to the person making the claim. That is their burden and theirs alone.

There is a purple elephant on the far side of the moon. There is data out there.

that’s equally credible to what you said (I.e. not at all as no evidence has been given).
 
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Cap'n Jack said:
I question whether there is enough feedstock, but the people producing the stuff are making a profit.
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Soybean oil. There is a rush in new crush plants being completed by 2026 that will add capacity to crush almost 500mm bushels of beans or a 20% increase. That is a little less than a billion gallons/yr mostly planned to go to refineries to crack.

...now about where are we going to find the 8mm additional acres to grow those beans.
 
Pinecone said:
The proof is left to the student.

The data is out there.

I cite a couple of articles as that is how many I read. I did not look for or read any more
Click to expand...
You cited no articles.
 
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