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: I'm sure the usual people will chime in and explain why it won't/can't work.
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 have no doubt the science behind the production of the fuel is sound. I question the economics of it all.
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
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.
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…
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? See below... 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 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. 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.
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. 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.
