Brazil is currently running a fleet of agricultural-use airplanes on 100% ethanol.
Probably. However, we can’t produce enough for ALL the cars AND the airplanes, so for this to work cars/trucks/buses/etc. would have to utilize something else, such as electricity or power cells or something. That would leave enough biofuel for the airplanes. Probably.
Probably convert to biodiesel. There are some issues with it, but they’re probably solvable with today’s technology given sufficient incentive. Ethanol is less dense as a fuel (you get less energy per unit of measure than diesel) and also has some issues, which means it’s less favorable for long-distance air travel although for short distance (such as agricultural uses) it works just fine.
The thing about jet engines is that in an airplane pretty much the optimal fuel is kerosene. Hydrogen isn’t viable simple because it has such low density, even in liquid form. The volume of hydrogen tanks needed would significantly impact on the design, even in liquid form. Further, moving to a cryogenic fuel is really a major ask.
The thing is to think of kerosene as an energy storage medium. Jet aircraft are much more finely balanced in their needs than most other transport systems. They really need the most optimal energy storage mechanism. And that is going to be kerosene for the foreseeable future. There just isn’t any other technology that gets even close. But that isn’t all that big a deal. We can convert other energy sources to store energy as kerosene. The raw materials are, after all, just carbon and hydrogen. Plenty of that about. There might be the complication that in the worst case we have to drag some oxygen off the the carbon and hydrogen first, but that is simply a matter of how much energy we need to put into the problem, and thus how much we are willing to pay. In a world with no fossil fuels at all, that is where we would be. However we have so much coal that running out is simply not on the horizon. So the cost of creating kerosene can be a lot lower. Still not exactly as cheap as it is now, but it all depends upon how much one is willing to pay. A middle ground starts with methane, of which we have lots. Still not as cheap as pumping oil out of the ground, but not insane either.
So the answer is very likely that airlines will continue to use kerosene to run their jet engines. They just won’t be getting it out of the ground, and it will cost more.
For all practical purposes, we will “run out” of underground crude oil when there is so little of it left that it’s not economically feasible to extract it, even if the price of a barrel of oil hits an astronomical level – say, 50-100 times its current price.
No, that does not mean that we will ever extract every last mL before we stop drilling.
So I promise to never use the phrase “run out of oil” in this thread ever again, and I will instead use the phrase “when the price point is reached when there is so little crude oil left underground that it’s not economically feasible to extract it, even if the price of a barrel of oil hits an astronomical level.”
P.S. I’m learning a lot from the discussions and the facts presented in this thread. Energy economics is a fascinating topic. Thanks, everyone.
The whole discussion assumes there will be no massive breakthroughs in either technology or energy before the oil reaches that point. I am doubtful this will happen. History has shown repeatedly that given the incentive, people can find all sorts of ways around problems. Fusion power could be an answer, So could anti-matter. So could reverting to hydrogen as a lift agent (Go, Zeppelins!). We will develop whatever is needed. Airlines and air travel as we now know it may be transformed beyond recognition, but we’ll still be traveling.
For that matter, the Puppeteers may have given us stepping disks by then!
Numerous SDMB threads have discussed this. Given that the fuel specifics & overall economics of all current and forecast lighter-than-air craft are spectacularly worse than airliners (and indeed than nearly all other forms of transport), barring unforeseen breakthroughs, it’s unlikely in a future where energy is expensive.
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For all practical purposes, we will “run out” of underground crude oil when there is so little of it left that it’s not economically feasible to extract it, even if the price of a barrel of oil hits an astronomical level – say, 50-100 times its current price.
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This is simply wrong. We will never ‘run out’ of crude oil. Not until the sun goes all red giant on us and burns the world to cinders, and by then we’ll have bigger problems. We’ll gradually stop using the stuff because at a certain price point (far below your ‘50-100 times its current price’, assuming you are adjusting for inflation) many alternatives that already exist, as well as alternatives being developed or that will be developed, will become economically viable. Several people in this thread have tried to tell you this in other ways, but you don’t seem to be getting it for some reason.
So, in summary, we will never run out of oil…and there are alternatives to using fossil fuels for jet fuel as well as everything else that already exist and aren’t commonly used today because oil is still relatively cheap and plentiful. When oil isn’t relatively cheap anymore we’ll gradually start cutting over to alternatives based on market demand.
This is a solvable infrastructure problem, if we decide to commit. The government could throw $100 billion (or whatever) of stimulus money to provide every gas station with one hydrogen pump and then mandate that all new construction must provide for one.
There are other fuels that could be implemented in a similar manner, again, if we got serious about it.
The vast majority of commercially produced hydrogen is made from natural gas. Hydrogen cannot be made cheaply enough by cracking water with renewable electricity. The math just doesn’t add up. For all intents and purposes, hydrogen is a fossil fuel.
What about dirigibles? Don’t forget that it wasn’t the hydrogen that burned so much as the gas bag. I am not sure how this work, but I imagine a large, non-flammable, gas bag filled with hydrogen under pressure in such a way that up to half of it can be turned into motive energy while still remaining buoyant. I think a major problem would be control, especially in high winds. Is any of this actually feasible?
You can actually run short and intermediate range air travel on ammonia, which can be produced by nuclear reactors. The Russians are also working on powering airplanes using LNG, but I don’t think it will work for long haul air travel.
There are fuels that can substitute for petroleum, but it is pretty hard to compete with a fuel that you can just pump out of the ground. These other fuels are going to have lot of problems competing until petroleum gets a lot more expensive and then the natural gas derivatives will be the next choice.
People who think that high speed rail will compete air travel in the US are people who didn’t bother to do the math. All high speed rail systems in the world run with a heavy subsidy except for the Tokyo-Nagoya line. When you build an airport, you are connected to every other city in the entire world. I can go to my local airport and fly to over 90 cities non-stop. Another 30 or 40 with one stop and most of the major cities in the world with one change of plane. It is hard to get around the fact that you don’t have to build sky.
Color me pessimist, but I can’t help but feel fatalistic about all this.
[side-note: I can’t believe that this built-in spelling checker doesn’t know “color”!]
Can somebody give some statistics about this?: How much fossil fuel have we used in the last 100 years? How much coal have we used in the last 1000 years? How long did it take to produce all that in the ground?
Are we burning (literally) through fossil fuel orders of magnitude vastly faster than it took to create it all? If so, then we are going to run out. Okay, so we won’t absolutely run out, but run low enough, and it will become expensive enough, that we will no longer be able to run the world as we have done for the last 100 years. And with all the emerging societies (China, India, etc.) piling on the demand too!
My doomsday prediction is that ultimately (perhaps in another three generations or so?) we will, for most practical purposes, run out. And I think md2000’s prediction of life in the 1950’s is too optimistic. I think the world population will necessarily collapse to about what it was in the late 1800’s, before fossil fuel (specifically, petroleum) was a major energy source, and our lifestyles will necessarily regress at least somewhat similarly.
The only alternative I can imagine is some major breakthrough in alternative energy, but I am pessimistic about that too. There will be on-going major energy investment required at least throughout the R&D phase, and I am skeptical that “we” (meaning collectively “all of us”) will have the foresight or economic or political will to do that until it becomes too late.
Disclaimer: I am a total lay-person on these subjects, and I am speaking primarily from a platform of utter pessimism and cynicism, and not from any actual technical knowledge of the subject. (ETA: You could tell this from my user name, if you read it right.)
ETA2: I have a quote to add, but the edit window will expire faster that I can google it up. Stay tuned . . .
Okay, here’s the famous quote I’m looking for, sort of. I know you’ve all heard this, or variations:
My grandfather rode a camel. My father drove a car. I fly my jet. My grandson will ride a camel.
– Widely cited quote in one variation or another (you can google up umpty-ump citations), often cited as “Saudi proverb” or “Modern Arab [or Saudi] proverb” or the like. Often attributed to Saudi oil minister Sheik Ahmed Zaki Yamani.
If you plan to haul your fuel around in an extremely un-dense form, you’ll exacerbate what’s already a major problem for lighter-than-air craft: drag. It takes a depressing amount of energy to drive a giant object through our atmosphere at speeds that are at all useful.
Eh. People who say that don’t really mean “there will be no oil molecules in existence,” what they mean is, “for practical purposes, we will run out of usable/affordable oil” which is pretty much what you’re saying, if I’m reading you right.
Meanwhile we are using it faster than it is being replaced, which is a formula pointing inexorably toward some kind of change in our habits at some point.
All airlines in the world run with a heavy subsidy, too. But even granting that, you’re correct that high-speed trains are not economically competitive with air travel in most of the US… right now. That will change, as oil (and eventually other fossil fuels) grows scarcer.
That isn’t true in the United States. Our air traffic systems are run on taxes on aviation fuel and passenger tickets, landing fees and fees charged on the various concessions at the airports.
That isn’t to say that airlines don’t want a subsidy and there is a feeling that General Aviation doesn’t really carry it’s weight.
When went over all these arguments on high speed rail versus air travel back in February. It would be more better to review the thread than rehash the same arguments.
We are nearing the point now where the rise in crude oil prices will become meaningless. It cannot rise indefinitely because we already have alternative fuels that can replace them at some price break point
We’ve also been testing and certifying these fuels for aircraft use so there will never be a problem with today’s jet technology and the fuels needed to operate them.
