United flies passenger flight on sustainable aviation fuel supplying one engine
ge.com
ge.com
I've followed this process for a while. It yields more energy than ordinary biomass approaches, since it can also incorporate the energy of the hydrogen input stream. This is good, because biomass has terrible efficiency at conversion of sunlight to fuel. No CO2 need be produced; the oxygen is carried away as water. One can think of the biomass as more of a carbon source than (just) an energy source. It also tolerates a wider variety of input molecules than enzyme-based approaches.
It sounds like the change is not how it burns, but how the feedstocks are generated. If the carbon is being pulled from the air (instead of the ground) at the start, then the overall process can be "low life-cycle carbon emissions relative to fuels from crude oil" (from the bioforming link).
Fortunately, it's also its own solution: if we find we need to avert a catastrophe next week, grounding all flights today might do the trick. But of course it's very hard to predict a tipping point to that level of accuracy. If we had that sort of movie-plot threat in climate change we might actually see meaningful action.
So yes, while carbon dioxide and methane are terrible, awful, no good gases we shouldn't be dumping into the atmosphere with quite such abandon, choosing to maintain water vapour at a particularly vulnerable point in the system is also something of an unforced error.
I feel unforced error is bit harsh too. Climate sustainability is a series of mostly hard problems, and aviation is one of the hard ones.
Perhaps there is an opportunity for a fuel additive that minimizes the formation of cirrus clouds, if the clouds are the source of so much of the climate impact.
Excess H2O (water vapor) falls out of the sky as rain, so it's fairly constant (ie. "maxed out"), and its long term concentration levels are a function of CO2 equivalent gases in the atmosphere. So if you increase CO2 levels, H20 levels will naturally increase as well, and vice versa.
Fossil-derived plastics make up a significant portion of household waste. From a climate perspective, it might actually be better to bury plastics in landfills rather than burn them as fuel.
The thing you've got to remember about plastics though is that only a relatively small fraction of the carbon involved in producing a lump of plastic is actually in the plastic itself. The production process emits a lot more. If what you end up doing is creating a demand for more raw plastic to be produced, that's a massive net loss.
I'm not enough of a chemist, but I suspect that the process the article is about could also habe potential for the creation of raw materials from bio stocks for plucking into the conventional plastics pipeline? This, combined with landfills (instead of incineration/highly processed incineration) could end up being the most viable carbon capture approach: instead of jumping through hoops trying to capture for the sake of it, it would harness our insatiable demand for plastics consumption. Are there any plant-based plastics already that don't don't with the friendly "degradable" label?
This runs the same risk as we currently see with recycling: because it all happens behind closed doors, the door's wide open for the worst sorts of environmental fraud where the claimed process actually only happens on a small fraction of the input, and the rest is just dumped. We really need plastics that can be broken down at the home level so people can take ownership of the process directly.
As a diesel replacement, I expect that price will be the blocker. If they can get the cost down to battery levels, great. Otherwise I think long-haul electric trucking will be practical enough where charging networks are practical enough, which is where most of the people are. Dog-sleds and camels may remain the best green alternative for some areas though :)
But, yes, if you can make one, you can almost certainly make a good simulation of the other.
The way this process does an end-run round that with added hydrogen is interesting, though.
(Transfer of turbulence to ground level may be a way wind turbines can increase agricultural yield, I think.)
That seems almost too good to be true. If the above is true, how does the cost, or the ability to scale up compare to traditional hydrocarbon fuels?
Something like that doesn’t seem impossible; there is so little coverage of chemistry in science news that the whole field is something of a blind spot for me.
Power-to-h2-to-power is 30% efficient.
Please.
Power-to-h2-to-power is much better than 30% efficient, btw.
Source for the "much better than 30%" efficient ? I want something that is deployed and in production. Not some kind of startup-that-will-change-everything tech.
- The technology to convert power to hydrogen and back to power has a round-trip efficiency of 18%-46%, according to data that Flora presented from the Massachusetts Institute of Technology and scientific journal Nature Energy. In comparison, two mature long-duration technologies, pumped-storage hydropower and compressed air energy storage, boast round-trip efficiencies of 70%-85% and 42%-67%, respectively. Flow batteries, a rechargeable fuel cell technology that is less mature, have a round-trip efficiency of 60%-80%. https://www.spglobal.com/marketintelligence/en/news-insights...
- https://www.volkswagenag.com/en/news/stories/2019/08/hydroge...
I hope you were assuming a combined cycle power plant was being used to turn the hydrogen back to power, not a simple cycle turbine only 2/3rds as efficient.
There are other storage technologies with higher efficiencies, but they also have much higher cost per kWh of storage capacity. On that metric batteries are like two orders of magnitude more expensive than hydrogen (flow batteries somewhat better but still much worse than hydrogen.) In storage use cases where it is appropriate (seasonal, rare event backup), hydrogen is hard to beat.
I get the feeling you're reading from a list of debunked pro-nuclear talking points.
I fail to see how this argument is "debunked". I'd also like to see what other arguments are on my supposed list.
[1] https://en.wikipedia.org/wiki/Energy_return_on_investment
The EROEI of nuclear is 106, by the link I previously provided. The very best solar installations have an EROEI of 7. That means nuclear gives 106/7 = 15x more energy output than solar, for a given amount of manufacturing energy input.
It's a simple ratio calculation, I'm not sure why you decided to subtract the reciprocals of the two numbers.
> Once EROI is high enough
The EROI of solar is 7, which means you get 7 units of energy output for every unit of energy expended in manufacturing. That is a terrible return. In no way is that "high enough". In fact, we shouldn't be bothering with it at all.
That sounds like a regurgitation of Ferroni and Hopkirk's analysis, which has been well debunked,
https://www.nrel.gov/docs/fy17osti/67901.pdf
The estimate for EROI of PV IN EUROPE is somewhere around 8, and of course Europe is a terrible place for solar -- the EROI for PV in a sunnier place, like Chile, Namibia, or the middle east, would be nearly twice this. If energy costs were really important, one would not put the PV factory in a place where energy were expensive.
That the EROI of solar is adequate should be obvious because the economic return on investment is good. If solar in Dubai can come in at less than $0.02/kWh then the energy cost (which will always be just a small fraction of the total manufacturing cost) will be reasonable.
Attempts to show PV has bad EROI very often run into methodological problems, extending the system boundaries beyond what analyses of the competing systems use (if you extend the boundary far enough, to the whole society, in steady state the EROI always converges to 1, since all energy produced is consumed somewhere. This is not a meaningful result.)
This is massive. Aircraft are some of the biggest CO2 pollutants out there.
Synthetic fuels will allow the existing fleet to be operated in a more sustainable way during this time. It will probably have a higher cost though. Long term, the low cost sustainable alternatives will probably take over. But as electricity production cost drops in the next decades, so will the cost of using electricity for producing synthetic fuels.
Just for fun - an acre of soy produces 70 gallons of "biofuel", so a square mile of soy plantation can produce around 45,000 gallons of fuel, or enough to fly a 747 for about 10,000 miles. After slashing and burning a patch of rainforest, you get about 3 years of crops, before you need to leave it for around 10 years to "regrow". If all of the Amazon rainforest (2,000,000 sq miles) was slashed and burned for soy plantations, and assuming it can magically regrow in those 10 years, we will get enough fuel over one 13-year cycle to fly 5 billion miles. That is about 1/10th the total airplane mileage in one year. [2]
[1] https://www.virent.com/products/jet-fuel/
[2] https://www.quora.com/How-many-miles-do-airplanes-fly-in-the...
It's possible to make sustainable jet fuel using trees from forests that aren't competing with food supply. Without that, yes, it's a bad idea. Anything involving soy or palm is usually also a bad sign. But in principle, nothing says you can't use "good" raw materials to produce fuel.
The UK has only just started reversing the almost complete deforestation it experienced due to human demand for fuel and materials. Once you start adding in calculations for "how sustainable is my product, once I've cut the trees down and have to wait for the forest to re-grow", you find that not much is sustainable at all.
To put it another way - by this proposed system, assuming 35mpg, an annual personal mileage of 5000 miles would need a dedicated installed solar capacity of 2kW nominal, assuming a 20% capacity factor. This takes up 15sq. meters. Mutiplied by the population of the US, that's 4,500sq km of solar, just for fuel for driving.
The majority of the energy content of the "sustainable" fuels in your scenario would have to come from sources other than the biomass feedstock. Sure solar generates more power per acre than photosysntheis, but it's very expensive - especially in a sustainable world where the solar panel factories are powered by solar panels, and not by coal.
It's not at all clear that PV is more expensive. In the best global locations it's already below $0.02/kWh -- and one would want to do this processing where the inputs are cheap.
Add to that: this is all forward looking, so we must also consider that PV will continue to get cheaper. Extending the historical experience curve to the point the world is solar powered will drop its cost by another factor of 4. This may or may not happen, but calls in the past that the experience curve had reached its limit were wrong.
If we're talking about renewable and sustainable power, the only way to look at it is the embodied energy of the device. As I alluded to, the only way solar panels are as cheap as they are is because they are all made using coal or other fossil power. Solar panels require an enormous amount of energy to manufacture - the energy payback period is over 20% of the panel's expected lifetime. This clearly indicates that the price per unit of energy in a system powered by solar would be much higher than it is now.
We also haven't even touched on the idea of where on earth (literally) all of the minerals required to make this gigantic number of solar panels, will come from. PS. Invest in mining, "renewables" are making it a very profitable business right now.
> Sustainable aviation fuel can be made from any of 60 different feedstocks — among them plant oils, algae, greases, fats, waste streams, alcohols, sugars, captured CO2 and other alternative feedstock sources and processes. The Department of Energy estimates that the United States alone has the resources to produce 50–60 billion gallons of SAF per year.
Ultimately, all of those "sustainable" feedstocks will have to be grown. As my quick maths points out, the size of the field we're going to need is just staggering.
>The Department of Energy estimates that the United States alone has the resources to produce 50–60 billion gallons of SAF per year.
I'd like to know where from. Actually, I looked it up. It's the "Billion Tonne Plan". It involves "thinning" all US forests, and planting practically every available acre with crops for biofuel. Basically, dedicating all of the available plant matter grown in the US to burning for transportation.
The amount of carbon in paper, cardboard, and food in existing municipal solid waste streams in the US would be nearly enough to make the current US jet fuel demand. It's not like replacing all liquid fuel use -- jet fuel is about 6% of US liquid fuel demand.
Assuming we use the hydrogen conversion process you mentioned, and have fitted the 1000's of square miles of solar panels it would need - I find it hard to believe that the US throws away 90 billion kg of carbon-rich domestic waste every year (apparently, the US gets through about 15 billion gallons of jet fuel per year).
Obviously, even if this is true, we then need to address the other 94% of liquid fossil fuel use.
Materials landfilled in MSW:
https://www.epa.gov/facts-and-figures-about-materials-waste-... https://www.statista.com/statistics/1231960/municipal-solid-...
The point is not necessarily to suggest that landfilled material be what is used to make jet fuel, but to point out the volumes are not enormous compared to what's already flowing through the economy. The US produces even more agricultural waste -- over 200 million tonnes of corn stover each year, for example.
The other fuel uses may in many cases be replaced by non-fuels, for example by electrification. Aviation is a special case where the high energy density of chemical fuels, and particularly hydrocarbons, will often be unavoidably attractive.
So far, you have suggested that we build several 1000 square miles of solar panels, and dedicate 90 billion kg of carbon-containing material annually, just to fuel 5% of the world population's aviation habit. How do you propose we replace the other 94% of that 5%'s liquid fuel use? After that, how about their total energy use (which dwarfs the total liquid fuel use)?
1000 square miles of land sounds like a lot, but for land at $1000/acre (which you can find in much of the US) that's $640M, or maybe 6% of the cost of a single one reactor nuclear power plant.
BTW, the world produces 2,000 million tonnes of municipal solid waste each year. The global production of agricultural waste is also very large. I also wonder how you're going to be fueling those nuclear powered aircraft, if not with carbon-containing synfuels.
I think you need to step back and ask yourself why you're allowing yourself to make such silly statements. You look like a person defending an irrational prejudice.
>The shipping argument is obviously wrong if you think about it even a little.
Humour me - how, exactly? How exactly is it "not a problem" to ship and install several thousand square miles of solar panels? Just for fun, here's another calculation for you to ignore:
To make the 15 billion gallons of jet fuel needed per year (for the US), you need 7.5 billion kg of hydrogen, requiring 375TWh (at 50 kWh/kg H2). Assuming an annual output of 360MWh per acre of solar, you need a million acres, or nearly 2000 square miles of solar panels (just to remind ourselves - this is just for jet fuel for the US, as you seem determined that this is feasible to do sustainably. I'm not sure what we will do about the other 99.9% of total US energy usage).
A commercial solar panel weighs 40 pounds and is 5ft by 3ft. Assuming they fit, you can load up a semi trailer with 1000 of those panels, for a total area of 15000 sq ft of solar per semi truck. You will need 4 million 18-wheeler loads of solar panels, for this proposed 2000 sq mile array. I'm not the one "handwaving away" the obvious difficulties here. The Evergreen container ship would need 200 journeys, loaded entirely with solar panels, to carry them all.
Apparently, installing the panels is the easy part. Hooking them all up to the grid is the time consuming part. I'm not sure what hooking up a 2000sq mile array would look like, as it is somewhere over 1000x greater than the current total world solar capacity.
Maybe the FAA could have been more aggressive in allowing a replacement fuel to be certified, but various fuels have been tested for over a decade now in experimental category aircraft, meaning they were not holding up development activities, just holding what seems like an objectivity reasonable hurdle for all-model STC approval (which still hasn’t been granted; we’re at the “many model” approval level right now).
I say that because this same story pops up every ~2-3 years, but the important question that never gets conveniently ignored in the articles is, they flew using plant-based fuel at what price?
Price is what determines everything for our behavior, including airlines deciding to fly planes all over the place. Reporters (and of course the press release) seem allergic to addressing such questions.
If you read a story about biofuels and it has no mention of the price of the fuel, you can bet it's pretty much a meaningless piece of news. There is not a single $ sign in the story.
It always turns out the fuel costs like $25 per gallon to produce. The basic concept that you can make fuel from biomass is not challenging. And flying it in a plane's gas tank is not new. Manufacturing it at a competitive price is.
What will happen is that this will go nowhere, because neither United Airlines nor any other carrier will pay that per gallon compared to the $6-7 they usually pay. Unless it's continuously subsidized. Or until a technology comes along to make the price much more economical.
Past examples:
2008: https://abcnews.go.com/Technology/story?id=4338149&page=1
2010: https://www.scientificamerican.com/gallery/military-green-us...
2011: https://www.npr.org/2011/09/26/140702387/air-force-and-navy-...
2016: https://www.biofuelsdigest.com/bdigest/2016/10/02/american-a...
2018: https://www.theguardian.com/environment/2018/jan/30/qantas-u...
Not a peep heard from these practically since.
Sorry this is a little negative. But if there is to be any informed / useful understanding of the topic (which I think this place is about), and not just feeling good after reading a story for 30 seconds, this is the key issue, not just the nice headline. Otherwise you go away for a couple years and wonder "hey what happened to that good news about achieving biofuels?"
It's like if I told you I demonstrated that we could run your car on biofuels. Great. At $25/gallon? Not so impressive.
The reason why you don't want to use straight kerosene is that it is too pure - diesel has additives that lubricate the engine, without which you will cause more wear and tear on the engine. If that's all you have it'll probably work though, especially if you mix it with a little engine oil.
1. The plane didn’t actually use 100% SAF
And it’s clear enough if you read the press release, as some of Twitter’s users did.
In fact, one engine was running with 100% SAF and the other with traditional jet fuel.
That’s because the US Federal Aviation Administration (FAA) allows for a 50% total of SAT to be used during a flight, United explains.
For this reason, SAF is basically employed by airlines as a drop-in fuel that gets blended with the conventional one at a 50-50 ratio. United decided to fly its plane with one SAT-powered engine and one fossil fuel-powered to demonstrate that “there are no operational differences between the two.”
This proves that an engine can run on this fuel at 100% concentration. The other engine is exactly the same, there's no reason that this result doesn't carry over to a flight with /both/ engines using this new fuel. This is just a safer test if there turned out to be problems with the experimental fuel.
The article mentions this in the very first paragraph, I don't think there's anything to complain about here.
I also don't think the headline is misleading either. The important thing being tested here is that the engine managed a flight with a 100% concentration of the new fuel, the other engine being a failsafe with known safe fuel doesn't make the outcome of the test any less useful.
Edit: the headline on the page mentions the second engine using legacy fuel, I'm not sure why the HN headline was modified.
My horrible, ostentatioous BAD! I mixed up the GE headline with the viral United Airlines tweet about the same exercise:
https://twitter.com/united/status/1466045020473942020
In which they took care not to mention the second engine using standard fuel, going so far as to say (this time quoting correctly):
Today, United will be the first in aviation history to fly a passenger flight using 100% sustainable aviation fuel (SAF).
This flight will serve as a turning point in the industry's effort to combat climate change.
But at the end of the day - my bad!
Earlier, ill-thought transmission (from me) follows below, as-is:
The point isn't the testing protocol, or that two different fuel types were used.
It's that these companies are trying to play with our heads.But (as noted in the article I linked to), apparently has significant scalability issues, and (because of sourcing and transport issues) is not "100 percent" emissions-free.
Do you mean the HN headline? As far as I can see, that's the source of consternation.
If one engine works entirely fine on a 100% blend, with no ill effects in operation or in analysis afterwards (for weird deposits on the hot section), it's reasonable to conclude that one could run exclusively on it.
There's a chunk of wisdom over in experimental aviation (the "You can build and fly whatever you want, please try not to kill anyone else in the process..." side of things): "Never test an experimental engine on an experimental airframe." If you're building a new airframe, use a proven engine. If you're trying a new engine, use a proven airframe. Otherwise you just end up with an explosion of possible issues, and "experimental engine plus experimental airframe" tends to lead to an alarmingly short lifespan.
Running one engine on an experimental fuel, while keeping the other on something you know is entirely sane and will work fine, is entirely reasonable. You know the airplane can fly and land safely on one. You think the other one works fine - but there are some weird corner cases in aviation - British Airways Flight 38 was one of those things. In this particular, exceedingly difficult to reproduce case, water in the fuel iced up and clogged the fuel flow to both engines, leading to a crash short of the runway (no fatalities, mostly due to the skill of the pilots). The engines behaved absolutely fine, until short final, at which point they suddenly, and without any prior warning, refused to make power - because they couldn't get enough fuel.
The entire point of testing is to work out as much of this sort of stuff as you can. If it turns out that after cruise, you've got weird fuel icing issues, it is far better to have that problem limited to one engine, where the other one can pick up the slack and haul you into a goaround if needed (twinjets are typically obscenely overpowered on two, because they need to perform well with an engine out).
Doing it the way United did is entirely sane, reasonable, and rational for any sort of aviation testing. Doing it on both engines, without serious testing beforehand (of the "on one side" variety), would be insane in aviation.
The article title doesn't have this issue because it clearly says "Supplying One Of Its Engines". I wonder if they added after getting criticized or if it was there all along. Edit: probably the former, since the original press release omitted it: https://www.prnewswire.com/news-releases/united-to-become-fi.... Pretty silly to think they could get away with that.
But from the company pushing the product.
"United Flies World’s First Passenger Flight On 100% Sustainable Aviation Fuel Supplying One Of Its Engines"
And it's in the url too.
> United Flies World’s First Passenger Flight On 100% Sustainable Aviation Fuel Supplying One Of Its Engines
Third sentence:
> It was the first commercial flight with passengers on board to use 100% drop-in sustainable aviation fuel (SAF) for one of the aircraft’s two engines.