Er... "using" 100 percent sustainable fuel ... in one of its engines. While in the other engine:
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.”
I am not sure the GP caught the article's statement that the regulatory cap on SAF is 50%, and that as a result this is arguably the most aggressive test UA could have run.
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.
So I definitely should have read the GE headline more closely (which doesn't make this obfuscation). But that's what happens when these companies keep lying, and lying, and lying - at some point your senses go numb, your eyes start to bleed... and you lose track of detail.
Nothing about it being modern is relevant to them missing specific information here. That's happened for centuries. But I agree nonetheless, we shouldn't fault the company for having a fail-safe
It's also unfair to blame the article. The actual press releases headline was correct and precise about this. The only place it got messed up was the HN headline.
A 50% reduction in the emissions associated with flying, with no additional changes to the infrastructure involved is a game changer. If we can do this for planes, then ships and trains aren't far off.
Yup - that's exactly the take-away they would like the reader to have.
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.
True. The point was that there’s a progression in the technology. Nickel Cadmium -> Lithium Ion -> ?Solid State. More importantly, there’s the cost curve improvement.
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.
> 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.
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.
This appears to be the synthetic jet fuel from Virent. It is made from light carbohydrates and other small organic molecules by their "Bioforming" process. This removes oxygen from the molecules by reaction in solution with hydrogen gas and a ruthenium catalyst. The resulting hydrocarbon molecules are then put through a reforming process where they are linked together and isomerized to get the right distribution of molecular weights.
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.
I saw this news while on a public place watching NHK Newsline. Interestingly I couldn’t find it on Google search under News or All. The very interesting part is that the feed stock used to make the liquid fuel comes from common garbage waste. Have we finally found a place for the tons of household garbage we generate? The company cited as the supplier was Fulcrum Bioenergy in Reno Nevada. https://fulcrum-bioenergy.com/
> ”Have we finally found a place for the tons of household garbage we generate?”
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 mirror argument is that from a climate perspective, as long as we are still burning low energy-per-co2 fossils like lignite for energy (spot the embarrassed German) it might be a net reduction if we burn those high energy future landfills instead. Plastics are very useful, perhaps we should consider it wasteful to leave any well-to-atmosphere paths where the carbon did not go through a stage of making itself useful as plastics? Hard to find any numbers, because the CO2/MWh stats of incineration plants always contain a considerable fraction of renewable on the input and that would have to be removed from the equation an all sides (input, CO2 output, energy output) for a useful answer.
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?
Probably the most common plant-based plastic is PLA. Or at least, that's the one I come across most often. While technically it's compostable, you need an industrial composting process to do it. It's not something you can just throw in the ground and dig up as usable soil a year later. And it's entirely possible that there would be ecosystem-unfriendly additives in it unless you were careful.
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.
There's a reasonable argument that turning them to biochar would enable us to enrinch soil enough to make it globally more efficient at capturing carbon. That would do both: the carbon in the plastics gets captured, and a carbon capture mechanism gets boosted.
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.
If it works as jet fuel it should also work as diesel fuel, as jet fuel is bascially high-grade diesel. That could be a benefit to railroads and long-haul trucking where batteries are not practical, as well as passenger cars, since the fuel delivery infrastructure is already well established.
It depends. Small organisms can potentially scale really well. If yeast, bacteria or algae can do what you want, you have at least some hope of scaling that up arbitrarily.
I think the idea is the microorganism you output some precursor(s) that you'd then process. If not, I guess you could pasteurize whatever it is, after filtering and such. Doesn't seem like it should be too much of a problem.
This is the problem algae farms all run headlong into: sunlight density. The energy output you get from doing anything with the biomass can't exceed the received sunlight energy times the photosynthetic efficiency of your microorganisms. And that efficiency might not be as good as solar cells.
The way this process does an end-run round that with added hydrogen is interesting, though.
I think algae farms are actually CO2 limited. Even a corn field, in calm air and bright sunlight, runs out of CO2 in about five minutes. And plants like corn have all those leaves above the ground for lots of mass transfer.
(Transfer of turbulence to ground level may be a way wind turbines can increase agricultural yield, I think.)
They're quite similar, and, in fact, there are plenty of engines that can run interchangeably on either (though possibly with a shorter lifespan on pure kerosene - it doesn't have much of the lubricity of diesel, so is really hard on fuel pumps, injectors, etc).
But, yes, if you can make one, you can almost certainly make a good simulation of the other.
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 :)
Could you clarify: is this a replacement for traditional hydrocarbon based co2 producing fuels that does not produce co2 gas as an output when burned?
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.
It means you can pull CO2 out of the air to make biomass (plants), then you can add (renewable) energy to the biomass to make it into fuel. When you burn the fuel, the CO2 is put back into the air.
Barring any nuclear processes, everything is carbon neutral as long as no fossilized combustibles are taken from the ground and released back into the eternal cycle of carbon neutral processes.
Really it nets to < 0, because there will always be a bunch of fuel sitting around waiting to be burned basically acting as captured carbon. This just doesn't accumulate over time so it's perhaps not really worth taking into account unless it is a massive amount of carbon.
Really it nets to >> 0 because you still make water from combustion, and condensation trails have a sizable impact on climate. They transmit visible light but are opaque to infrared, just like a greenhouse. Still better than fossil fuel, though.
Ah, cool, a red herring. Where did you get your atmospheric science degree? I got mine at UC Davis. Can you explain to me how the radiative forcing is less because it reaches steady state so quickly? The regime in the upper troposphere around the 250mb level is poor in ice condensation nuclei and the phase change is an irreversible thermodynamic process. Most of the time those parcels don’t condense easily, and the forcing is quite large as we observed in the 9/11 studies.
The point is that the water we inject into the atmosphere does not accumulate in the atmosphere. Once that water rains out it's in that enormous bucket that is the oceans (and to a lesser extent fresh water and ice), and the effect is gone. Emission of CO2, on the other hand, perturbs atmospheric CO2 level for a much longer time -- the reservoirs at the surface it's in intimate contact with are much smaller and more easily saturated.
And where the electricity come from ? Ah yes, hydrogen is 95% made from fossil fuels for now. "But soon we will make it from solar panels and wind turbines".
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.
It's a safe bet that hydrogen can be made without fossil fuels. Since hydrogen is essential to maintaining current world population (via manufacture of nitrogen fertilizer), if that were false we'd be doomed.
So you didn't answered my question regarding your sources. Here's mine:
- 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...
You will notice that 46% > 30%, so you have confirmed my statement and contradicted your own. Thanks!
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.
Fascinating argument, but unfortunately, we are doomed. That is, unless we go nuclear. Apart from that, there is nowhere near enough energy or resources to maintain our current lifestyle (and that's ignoring the fact that the vast majority of the world's population don't enjoy this lifestyle and very much wish to) in a "renewable" fashion.
There is absolutely no reason to assume that nuclear energy will be cheaper than wind and solar. For hydrogen production the "base load!!" argument doesn't apply either. You can just produce hydrogen when power is plentiful.
Just fine, if you're happy with approximately 1/4th the energy output for a given (manufacturing) energy input. And that's for the best case, for certain wind power installations. Solar is the worst, at about 1/15th the energy output for the same energy input (compared to nuclear). [1]
I fail to see how this argument is "debunked". I'd also like to see what other arguments are on my supposed list.
By 1/4th, do you mean 1/4th of nuclear? Sure, I'm totally happy with that. Once EROI is high enough, further improvement has only marginal effect. If EROI of PV is 10 (say) and nuclear is 40 (say), that just means nuclear is 1/10 - 1/40 or .075 better than PV by this metric. The contribution of this to the cost difference is minor, and is swamped by the other contributions to the cost of nuclear.
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.
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.)
For this the hydrogen likely comes from natural gas, but it will eventually come from renewable electricity via electrolysis ("green hydrogen") when CO2 fees are high enough.
Which will make fuel much more expensive, and thus less consumed (which is really what is needed). Obviously that will also mean poor people can't travel very far, but what are you going to do about that? Maybe just hand out a universal ration of 1 gallon of biofuel per year per person.
Their fuels burn the same as conventional fuels (that seems to be the point). The fuel needs carbon to have the right properties and when you burn it, the carbon atoms have to go somewhere. CO2 is the best option, carbon monoxide and soot are worse.
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).
H2O is actually a significant greenhouse gas from jets. Water is the most significant, giving Earth +30°C of warming, but most of the time we’re maxed out on that already. Still, in the dry upper troposphere, contrails make a pretty sizable contribution to AGW. Even in a carbon-neutral system, where you emit your GGs makes a difference.
Long term, CO2's worse, but that's probably not the best way to look at it.
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.
Water gives slightly more radiative forcing than CO2 from airplanes, and the effects of NOx are negligible. But of course the water disappears from that altitude in hours, while CO2 has a long atmospheric residence time.
The article implies that the radiative forcing is from the contrail clouds, not from the water per se.
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.
A very short term difference. We would not make much of a dent (or bump, if you are into being literal) in the thermal balance of our planet if our greenhouse gas activities did not involve unearthing large quantities of carbon that had been buried away "forever" in climate timescale. Years are not the issue, the problem is that everything we unearth won't re-bury itself in centuries and millennia.
The difficulty is in catastrophe curves. While the water from a single flight doesn't hang around long, there are always aircraft in the sky, so it's constantly getting refreshed and amounts to a constant thermal load. If that additional thermal load, on top of the other greenhouse gases, is enough to tip some nonlinear system past its tipping point, then we've still got a problem.
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.
You misspelled “radiative forcing” as “thermal load” but the analysis is correct. We did in fact shut down flights on 9/11 and that’s when we noticed the cooling. The tipping points are like, well, there are millions of them and they all interact with each other, thus computer models.
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.
Water is a far more efficient insulator than CO2 at more than double heat retention. This is mathematically tolerable due to atmospheric life cycle duration. Water vapor has an atmosphere duration of about 8 days before recapture at the surface but CO2 remains in the atmosphere for 72 days.
In a net zero scenario, we should start to see improvement in a couple centuries. The ocean overturning time is roughly 500 years, and getting carbonic acid under the carbonate compensation depth can have a huge effect, dwarfing anything we do in the terrestrial biosphere like “planting trees”.
A step in the right direction. Would be interested to know what the comparative energy ghg lifecycle costs for this fuel vs conventional fuel - and what prohibits them from using both engines. Is it just a liability / pilot test on the first go and then switch to both engines? Or are there concerns about going fully SAF?
Aviation is extremely conservative when it comes to adopting any new technology. It is tested and tested and tested again. Allowing only 50% (or 100% on one engine) seems like exactly what they would do. Make a small change, test it for a while, tear down some engines and look for anything unusual, etc. If it's a drop-in replacement for Jet A, it needs to work in the newest modern engines as well as the 30 year old ones that are still in service. Look how long it took to get unleaded gasoline approved as an aviation fuel for piston-engined aircraft.
Part of the difficulty is that the certifications for the (high-compression piston) engines were to run on 100LL, not to run on “a fuel with a lean mixture knock value of X and a rich mixture knock value of Y” and the specification for 100LL (ASTM D 910) is a formulation specification which includes tetraethyl lead rather than being a performance specification.
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).
There are a few methods out there for synthesizing gasoline equivalents. This fuel: no (possibly in diesel engines, jet fuel has been used but there are issues).
One interesting aspect buried deeper in the release is that United has gone out to make extensive financial commitments to get this fuel produced at greater scale. Putting these fuels to use is more than just testing.
I can't really see what the risk would have been. It's just liquid fuel and will mostly work or not work. They would have already tested heat generation and build-up of deposits etc. for many months.
> 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. For context, commercial airlines will use about 57 billion gallons of fuel by the end of 2021, down from a peak of 95 billion gallons in 2019, according to Statista. By switching from petroleum to SAF — when you take into consideration the entire life cycle of the fuel — the aviation industry could reduce its carbon contribution from fuel by up to 80%, according to industry associations the Air Transport Action Group and the International Air Transport Association.
This is massive. Aircraft are some of the biggest CO2 pollutants out there.
It's important because planes are expensive and have operational lives measured in decades. So, even though companies like Boeing and Airbus are looking at alternative forms of propulsion now (e.g. hydrogen and electric), it would take well into the second half of the century to replace the existing fleet with their newer, more sustainable versions. Realistically production for that kind of plane won't even start until the 2030s at the earliest (and probably in low volume initially).
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.
I hope this is part of a new positive development. But to me it sounds like one more in a series about biofuel that has generally gone nowhere or hit some limit that is not getting better.
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.
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.
This is completely bogus. The ever-increasing global demand for soy foodstock is already accelerating the destruction of tropical rainforests - how is it all sustainable to burn huge amounts of foodstock that so we can enjoy making the world "a smaller and better place" [1]?
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]
> 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.
By "article", you mean "marketing blub from someone trying to sell you something".
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.
It's bogus that jet fuel can be renewable, at least in anywhere near the quantity we currently use. Mainly because the amount of arable land needed is staggering, and we already are destroying virgin rainforest just to feed the world.
I mean sure, you can reach that conclusion if your number is off by a factor of 30.
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.
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.
Do you really think that our current lifestyle is at all sustainable, without using nuclear power?
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)?
Absolutely. Nuclear power is neither necessary nor particularly useful. Not only is it too expensive, but if used to power the world it requires either breeders (which have not been found to be competitive with our current burner reactors) or very aggressively cheap sea water uranium extraction.
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 don't even care about the cost of the land, it's the mind-boggling amount of solar panels that would need to be manufactured to fill it. Have a think about how the panels would get shipped and fitted in this proposed facility - the panels would start degrading and reaching end of life before you could get anywhere near completion.
Look, you're arguing by vague feeling and handwaving there, not by calculation. If you actually look at the numbers, solar's going to be cheaper than nuclear here. The shipping argument is obviously wrong if you think about it even a little.
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.
Not sure how you can say that, when almost every comment I've ever made to you has had some kind of calculation in it. Sounds like it is you who is attempting to dismiss arguments with hand-waving. How can solar possibly be cheaper per unit of power than nuclear? Do you understand how EROEI works? It's about 15x greater for nuclear than solar, which is about the most inefficient way to generate power.
>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.
This works off of carbohydrates and lignin, including cellulose. Assuming (CH2O)n + nH2 --> (CH2)n + nH2O, then 46% of the weight of dry biomass turns to fuel. The yield of Miscanthus is about 16 dry tonnes/acre/year. Jet fuel is 3 kg/gallon, so this would be about 2400 gallons/acre/year.
Just eyeballing that, it's 2 grams of hydrogen per 30 grams of carbohydrate. So, about 1 tonne/acre/year, or maybe half a kilogram per gallon. The hydrogen right now almost certainly is tapped off existing industrial supply, which comes from natural gas, but there's no reason one couldn't use "green hydrogen" from renewable-powered electrolysis instead. PV produces much more energy/acre than biomass does (and can produce it even outside the growing season), so this wouldn't increase land use very much.
Generating 500g hydrogen requires 25kWh (and a perfectly-efficient electrolyser would require 20kWh). One gallon of fuel has about 40kWh of energy available.
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.
Right. Using biomass to generate that hydrogen would be bad. Biomass, among all the renewable energy sources, has very poor power/area. PV is an order of magnitude better.
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.
Using the advertised final cost of electricity is, in my opinion, a useless way to work out the sustainability of any power source. It is skewed beyond usefulness by government incentives, tax breaks, etc etc.
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.
Using foodstock, or land that even competes with foodstock, or land that is important for sensitive ecosystems or CO2 balance is obviously all out of the question if this technology is to be viable.
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.
Arguably the Amazon rainforest isn't competing with food supply, at least on a global scale.
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.
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[ 3.0 ms ] story [ 160 ms ] threadMy 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):
So I definitely should have read the GE headline more closely (which doesn't make this obfuscation). But that's what happens when these companies keep lying, and lying, and lying - at some point your senses go numb, your eyes start to bleed... and you lose track of detail.But at the end of the day - my bad!
Earlier, ill-thought transmission (from me) follows below, as-is:
Do you mean the HN headline? As far as I can see, that's the source of consternation.
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.
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.
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.
> 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.
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.
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.
https://www.virent.com/products/jet-fuel/
https://www.virent.com/technology/bioforming/
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.
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.
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.
https://www.google.com/search?q=diesel+bug
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.)
But, yes, if you can make one, you can almost certainly make a good simulation of the other.
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 :)
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.
https://www.patentguru.com/assignee/fulcrum-bioenergy-inc
https://patents.google.com/patent/EP2534122A4/en
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.)
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).
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.
https://www.nature.com/articles/s41467-018-04068-0
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.
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.
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).
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.
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.
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...
> 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.
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.
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.