So this process is "CO2 hydrogenation" meaning that it needs elemental hydrogen, which is not naturally available (except in trace amounts). To make this work one needs to first produce hydrogen which is itself an energy consuming process.
So basically, we'd burn fossil fuels producing CO2 and then reverse this process via "CO2 hydrogenation" (with significant losses) to again get the hydrocarbons (aka gasoline) ?
This whole thing would only make sense if we had abundant source of elemental hydrogen. But then why burn fuel in the first place.
(This would only make sense if all fuel totally ran out and then we'd need this process to make hydrocarbons for material use: plastics, etc..)
Can also make sense if this is cheaper than batteries.
Electrolytic hydrogen is so easy I did it when I was nine years old — the only reason I powered the reaction using a battery instead of PV was that back in 1992, PV wasn't something a kid could easily get hold of with pocket money.
PV is so cheap the efficiency is the least important part of this.
PV without batteries is the cheapest power source on earth, bids in the order of single US ¢ / kWh, but last I saw batteries had LCOE comparable with nuclear reactors (about 15¢/kWh in 2020).
I’m certainly hopeful that batteries will improve, but right now even a mere 10% efficient process for turning electricity into gasoline and then burning it is still useful as both heating and aviation fuel, and just about on the edge of useful as strategic diversity for nations that don’t want to limit strategic energy storage to just batteries.
PV needs physical resources that aren't for free or unlimited. PV needs space. Most energy used has still an high negative impact on the atmosphere. Low efficiency somewhere is energy potentially wasted that could reduce carbon emissions somewhere else.
Heating is waaay more efficient with heat pumps. Aviation... Well who can still afford it...
There are other forms of storage as well, e.g. hydro, heat storage, and many more
I'm not saying it doesn't have it's uses, but efficiency is important
> Heating is waaay more efficient with heat pumps.
Absolutely.
With electricity you can power heat pumps (which are say, 5x more efficient than resistive heaters), but by synthesizing fuels with electricity, you can get strictly less than a resistive heater's equivalent energy.
Oddly enough (but not really that odd) it seems to be affordable to a lot of people who jet around the globe to tell each-other and the media that people need to fly less, for the climate. It used to be for the environment but that trope seems to be worn out.
> PV needs physical resources that aren't for free or unlimited. PV needs space.
We have about 10,000 times as much space as we need for a pure-solar economy at current power use, 1,000 times what we need if we raise everyone to the power use of the average American, but still better than 100 times what we need if we want to do that while having a 10% efficient storage system because most energy is used while the sun is up anyway.
> Most energy used has still an high negative impact on the atmosphere.
Yup, and will do until it’s renewable. If it was already renewable, using that power to make more renewables has no impact whatsoever.
> Low efficiency somewhere is energy potentially wasted that could reduce carbon emissions somewhere else.
Sure, but the ideal is a global superconducting grid, and even if you do that the easy way [0] we’re a long way from the necessary industrial base to get it done.
This option is sufficiently good to be interesting in the meantime.
[0] a ballistic superconductor, specifically a charged non-conductive ring in orbit.
Second best option: a few square meter cross section HVDC cable encircling the planet, which needs quite a big investment in mining to get the materials for but has the advantage we can get most of it done gradually just by continuously upgrading existing grids until the very last step of crossing the Atlantic and/or Pacific.
Not to mention that it requires capturing and probably liquifying the CO2 first, which is also energy intense.
If we do CO2 Hydrogenation, it will be for Methane gases, not liquid. Methane is easy to store, has rather flexible uses and would help in keeping the grid stable.
Liquids, especially when used in ICE engines later on, would result in an energy efficiency of 5-10% max. This is abysmal and we could use that otherwise wasted energy to decarbonize many other things by directly electrifying them.
It is hilarious how many people think the problem is with reversing the CO2 creation. No, it's a matter of getting the joules to sustain the modern lifestyle and the population count.
Primary energy assessment follows certain rules[note 1] to ease measurement of different kinds of energy. These rules are controversial. Water and air flow energy that drives hydro and wind turbines, and sunlight that powers solar panels, are not taken as PE, which is set at the electric energy produced. But fossil and nuclear energy are set at the reaction heat which is about 3 times the electric energy. This measurement difference can lead to underestimating the economic contribution of renewable energy.[7]
Wait, does the mean that if we wanted to use solar as an energy source for the world we would need to cover roughly 1/1700 of the entire surface of the planet with perfectly efficient panels and interconnections between the east and the west to support the energy transfer during nighttime ?
Wouldn't absorbing 0.06% of the incoming solar energy have a significant impact on the planet's ecosystems, either by the absorbed energy by the massive production of PV and storage required for that end ?
I think that your statement does not rebutt the parent comment : producing the energy required to sustain our modern lifestyle and population count will have significant impacts on the ecosystems, whatever the source we use for that energy.
All generated primary energy will eventually be turned into heat. However, the climate effect of this direct heating is orders of magnitude smaller than the greenhouse effect from burning hydrocarbons.
Indeed, there is hope! And note how fast the renewables portion is growing, we're looking at a fairly good projection here: 1, 2, maybe 3 decades ahead of us it should get really substantial. The biggest problem is the EROEI, which is a lot higher for the clean stuff, though still improving.
> That says global 'consumption' is about 80000 TWh a year. Incoming solar energy is about 1700 times that
Assuming that you still want oceans to work, about 2/3rds of that is not available, which get us to 500x. You also want land-based plants to work, which gets us to <250x and much of the remainder is unsuitable, so let's call it <100x.
"make equipment" through end-use solar is <20%, so we're down to <20x.
Why do this? Because we don't have electric or hydrogen airplanes yet, and it takes forever to approve an airplane and for it to become widespread.
Even if it is only 10% efficient, some form of carbon capture is going to be required to hit carbon zero. This is one of the most promising mechanisms for carbon capture.
What if you had massive amounts of virtually free energy just falling out of the sky in one or a few isolated locations, but only for a few hours every day, and your consumption patterns required an available-24-by-7 safely transportable consumer-safety-level supply?
Carbon-hydrogen bonds are an relatively efficient and safe way of storing energy and we have well-developed technology and infrastructure in place to take advantage of that.
> This whole thing would only make sense if we had abundant source of elemental hydrogen. But then why burn fuel in the first place.
water is an easy elemental source of hydrogen. If it is possible to fuel this electrolysis via cheaply obtained renewable energy, then it makes a lot of sense to produce fossil fuels using this method - it will allow the existing infrastructure to consume such produced fuels, so you save capital and energy on replacing them.
Absolutely. Look at intraday electricity prices, and you see that the energy is cheapest when the sun is shining.
Problem is, if you use it for cooling, it's strictly better to use the electricity directly (chances are the sun is shining when it's hot).
And if you use it for heating (at least from day to night), the round-trip efficiency is probably still better for batteries, or electric heating + hot water storage, because you can use heat pumps which are say, 5x more efficient than burning fuel.
Eh... There are more uses for fuel than cooling and heating.
If you have an stationary application you will never use something like that. (Except maybe for long time storage, I don't think this will win over long time storage, but it isn't settled.)
This requires batteries which are very heavy. This is not a big problem in cars, but an absolute deal breaker in aircraft. The energy consumption of a plane scales roughly with the weight, which makes efficient battery powered flight pretty much impossible.
Current battery tech just isn't that good. A Tesla battery pack weighs 900 pounds and only holds the energy of 3 gallons of gas. They are also a hell of a lot more expensive and wear faster than a gas tank.
Carbon hydrogen bonds are one of the best ways to store energy that we have.
Hydrocarbon fuels are a lot more energy dense than batteries or hydrogen (with tankage), so they are needed for things like long distance flight for now.
Batteries aren't great for super-cold areas. Pure hydrogen, my understanding is that it's pretty much impossible to make a 'leak free' tank. So for things like backup power generation there is an additional challenge. More thinking about need to top off than risks, I'm not qualified to speak to whether such a tank would be a risk.
Right battery chemistries with right thermal management and especially right software would work well also in cold climates. Bjørn Nyland from Norway tests a lot of this stuff on youtube.
I don't think that leakage is a serious issue in high-pressure hydrogen storage. The tanks used in hydrogen fuel cell vehicles have leakage rates of a few mL/minute [1]. The first generation Toyota Mirai has a storage capacity of 85000 standard liters of hydrogen. It would take tens of years to leak out a significant fraction of that.
They also make for great storage. Using solar to make a hydrocarbon fuel which is turned into electricity in our existing fossil fuel infrastructure seems way more plausible than spending trillions on batteries or pumped hydro.
Fossil fuels are cheaper because nature did the energy intensive "turn dinosaurs into oil" part (i.e creating the hydrocarbon molecules) for us over the span of millions of years and we just extract it from the ground and do some chemistry magic to make it into useful stuff.
The "create the useful hydrocarbon out of atmospheric carbon" step needs to necessarily be cheaper than getting dead dinosaurs to a refinery and refining them.
Screeching about externalities adds nothing to the discussion. Burning synthetic hydrocarbon fuel would also release carbon. A CO2 tax would hit it just as hard as it hits traditional hydrocarbon fuels unless you do stupid "craft the tax to pick and choose winners" crap that a carbon tax is explicitly supposed to avoid.
Elon Musk once pointed to the low energi state of CO2 as a problem meaning it doesn't react with other things without additional energy added. This makes carbon capture fundamentally hard and anyone claiming otherwise is either in possession of some infinite power supply or we live in a post scarcity society.
Either way, planting trees appears to be a good mechanism for carbon capture. So go do that instead!
Some activities are much more difficult to do with electricity because of the weight of batteries or because the environment is cold, flying planes or existing in Arctic climates being the most notable. So if we want a totally carbon-neutral world while still being able to do everything we can today, some carbon capture is important.
Hopefully we’ll have a huge innovation in batteries, but oil is very energy dense and some burning seems likely for a long time. We also will probably want to reduce CO2 levels from wherever we peak, even assuming we’re not burning any more oil, so carbon capture is important for that too.
Now some of that carbon capture can be in the form of well managed trees, but they take up a lot of land and you have to chop them down and store the wood somewhere that it won’t break down, and that becomes its own storage problem.
If this worked, then you'd still need it to be better than using the money expended to offset other other fossil carbon usage, one means of which could be converting gasoline using processes to use electricity directly.
As a result, I don't think this can ever make logical sense under any circumstances, very similar to carbon capture attached to fossil fuel generators. It just doesn't pencil out, even in theory.
Basically, gasoline isn't a particularly good fuel unless society is letting you dump the pollution for free, in which case it still isn't particularly good, but some other sucker is paying the price for it. And that other sucker is often you.
Hydrocarbons are fantastic fuels when high energy density is required. In fact, airliners would be completely impossible without them. Even the most fantastic experimental batteries have nowhere near enough energy density for efficient powered flight. There are some plausible concepts for hydrogen powered planes, but those waste a lot more space on fuel tanks compared to hydrocarbon powered ones.
Synthetic hydrocarbons will probably remain the only option for carbon-neutral long-distance travel in the foreseeable future.
Simply offsetting the carbon, by replacing fossil fuel uses in other sectors, makes more financial/economic/practical sense than creating synthetic hydrocarbons to greenwash your own specific usage. People really are stuck in a fossil-fuel mindset when the real solution is to stop using them as fast as possible. A simple carbon fee does this without much fuss. People peddling synthetic hydrocarbons are, again like carbon capture and storage attached to fossil fuel generators, simply bullshitting. They might as well claim to be transitioning to perpetual motion powered flight that they have working today at lab scale. Because, basically that is what they are saying.
but tomorrow, in that we expect a lot of growth in aviation. That might not be the case, why take a lover for a weekend to Paris when you can go to Montréal? A nuclear powered aircraft carrier could synthesize jet fuel from the ocean and atmosphere and even if it is $15 a gallon it is a bargain -- so the US Military sponsors this kind of research.
The best case for carbon capture now is this technology
applied to sugar cane alcohol factories in Brazil. You can catch CO2 from fermentation and not have to separate it from N2, compress to 1500 psi and inject into a saline aquifer. Those bioenergy plants are much better than bioenergy plants in the US by any economic or environmental metric. They'd have to get paid something per ton of CO2 captured to make it worth it. This industry is located close to populated areas such as São Paulo and does no harm to rainforests that Brazil must also protect.
Another case is the petrochemical industry in the southern US where CO2 streams are abundant and could be aggregated for scalable saline injection.
Any sort of space manufacturing will require a "circular economy" for carbon (it's precious) and whatever passes for a "petrochemical factory" will produce CO2 and that needs to have energy put into it into some form that can be put back into the "head end", methane would be great. The unique opportunity there is very high temperature chemistry with 24-7 sunlight concentrated with metallized plastic membranes made from the produce of the "petrochemical factory".
I'm optimistic about turquoise hydrogen, which is effectively the same thing as your bioenergy link, except you don't burn the biofuel then capture the CO2 you just remove solid carbon from it, and use the hydrogen as a chemical feedstock (or, if really, really necessary and there's literally no other option, as a fuel). And the key reason that would be better, is because burning biofuel is kind of crappy, just like burning fossil fuel is, and you're better off just directly using the cheap renewable electrical energy that you're going to waste seperating and storing the CO2 you create.
I'm also fairly sure electrical flight will be a thing long before we get to the last 3.5% of fossil fuel use anywhere on earth. Gasoline isn't magic, it's just something that we had a lot of lying around and didn't punish people for polluting and killing people with it, because the people with access to it became politically influential. That's it's only unique advantage, which thankfully seems to finally be fading.
How long ago were EVs totally impossible because of the amazing energy density of gasoline? Like 5 years maybe, and now that's laughable. EVs are clearly better. Did gasoline get suddently less energy dense in that period or was that always just BS supported by nothing more than status quo bias?
No, EVs were not "totally impossible" 5 years ago. The first GM EV1s with NiMH batteries were produced 23 years ago, and the first Tesla roadsters with Li-ion batteries 14 years ago. The battery capacity and weight of the roadster are not dramatically different from that of modern EVs.
In vehicles, energy density is not terribly important. The issue has always been the price of the cells. Only very recently they started becoming cost competitive compared to ICE powered vehicles.
The situation is very different in airplanes. At takeoff, something like 40% of the total mass of an airliner is just fuel. The best Li-ion cells have something like 50 times lower energy density than kerosine. It is simply not possible to fly any useful distance with such a low energy density.
Famous and highly cited energy theorist Vaclav Smil was still calling them an overhyped dead end 5 years ago, a decade ago he said "The myth that the future belongs to electric cars is one of the original misconceptions of the modern energy era".
And he literally wrote a book published in 2015 on the topic of energy density.
So I'm glad it's obvious now with 20/20 hindsight, but it seems a lot of people can be wrong about this stuff and have their opinions promoted.
It doesn’t make sense for cars (electricity is a practical alternative and if you wanted to use chemical fuels you would synthesize methane or 1-butanol, dimethyl ether or some other single-entity fuel for which the production process can be optimized)
Aviation is 30-40 years behind in fuels (they still use leaded gas.). The kind of Fischer-Tropsch chemistry that these guys are messing with has been basically abandoned for automotive use but is still being pursued for jet fuel because they are afraid to use any fuel which isn’t identical to existing fuels in composition…
Traditionally these processes start with a stream of hydrogen and carbon monoxide which can be made from coal or methane, the economics are gawdawful because the reactions that build up hydrocarbons and break them down have to be closely balanced —- polyethylene formation can be explosive, methane forms quickly if the temperature is too high. What it means is you have a big machine (high capital cost) that makes just a trickle of fuel. In the green era people like these guys are mixing up the chemistry so you can put CO2 in instead.
I have been thinking about how you would make plastic membranes from asteroid materials, we think some asteroids have something that is basically coal and the head end would turn that into ‘petrochemicals’ and might have a lot in common with fuel synthesizers… A lot of chemical processes will create waste CO2 which is precious in that context and has to be recycled.
The only place aviation uses leaded gas is in the small, piston engine part of the market that represents primary training or hobbyist/personal transportation flying. In those cases, it's more like engine designs are 70 or 80 years behind current designs; and oftentimes the actual aircraft are not much younger.
There's no lead in jet fuel, and I'm just not exactly sure what you mean by aviation being "behind" in fuels in that respect. What's the leading edge supposed to be, in gas turbine technology, other than essentially kerosene?
Jet A is just fine in the context that you are making it from crude oil and you don’t mind the CO2 emissions.
If you want to make carbon neutral jet fuel based on biomass or direct captured CO2 on the other hand, kero is terribly hard to synthesize. Back in the bad old days politically isolated countries such as Nazi Germany and apartheid South Africa built expensive factories to make gasoline and diesel from coal using the same kind of chemistry that the authors of that paper are using.
Even then the economics were so bad it was an act of desperation and nobody would be attempting to synthesize hydrocarbons for ground transportation today because we have batteries, fuel cells, methane, alcohol and other fuels that can be bio based or synthesized more easily.
The Jet A problem is different from the leaded avgas problem but it comes from the same root that if your engine stalls out because of a fuel problem (say water separates out, freezes, clogs your fuel lines and all the engines fail) you have to hurry and find a place to land pretty quick, whereas if it happens to your car it is not so bad. There’s that any and also an unwillingness to make aviators upgrade their hardware (look at the 5G vs altimeters fight.)
> .. you would synthesize methane or 1-butanol, dimethyl ether or some other single-entity fuel ...
I agree that simple fuels makes more sense to synthesize.
Methane is simple, but way more difficult to handle than gasoline.
1-butanol and other liquids would be great, but it is not so easy to produce in scale yet, I believe.
Methane is very low cost (where pipeline networks exist), will probably still be comparatively low cost in the synthetic fuel age, and is much easier to handle than hydrogen. Big airports could have LNG plants on site, smaller ones would have to truck it in.
Methane-based planes might have a lower TCO if the industry made the switch but the switch would be hard.
I don't think you can talk about the engines being the problem if the supposed alternative to kerosene-type fuels are methane and alcohol - the engines are probably the easy part of the problem there; it's the pressurization or cryogenic requirement for methane and the significantly lower (~half?) mass energy density for alcohol fuels.
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[ 3.9 ms ] story [ 140 ms ] threadCan anyone spot how efficient it is? It declares that it's "Highly efficient", but then no details on what the actual efficiency is.
Or maybe cars would be equipped with a tank that compresses CO2, but even then.
It's funny how the solution is all about stopping to use fossil fuels, but people still find ways to CREATE fossil fuels.
So basically, we'd burn fossil fuels producing CO2 and then reverse this process via "CO2 hydrogenation" (with significant losses) to again get the hydrocarbons (aka gasoline) ?
This whole thing would only make sense if we had abundant source of elemental hydrogen. But then why burn fuel in the first place.
(This would only make sense if all fuel totally ran out and then we'd need this process to make hydrocarbons for material use: plastics, etc..)
Electrolytic hydrogen is so easy I did it when I was nine years old — the only reason I powered the reaction using a battery instead of PV was that back in 1992, PV wasn't something a kid could easily get hold of with pocket money.
PV without batteries is the cheapest power source on earth, bids in the order of single US ¢ / kWh, but last I saw batteries had LCOE comparable with nuclear reactors (about 15¢/kWh in 2020).
I’m certainly hopeful that batteries will improve, but right now even a mere 10% efficient process for turning electricity into gasoline and then burning it is still useful as both heating and aviation fuel, and just about on the edge of useful as strategic diversity for nations that don’t want to limit strategic energy storage to just batteries.
Heating is waaay more efficient with heat pumps. Aviation... Well who can still afford it...
There are other forms of storage as well, e.g. hydro, heat storage, and many more
I'm not saying it doesn't have it's uses, but efficiency is important
Absolutely.
With electricity you can power heat pumps (which are say, 5x more efficient than resistive heaters), but by synthesizing fuels with electricity, you can get strictly less than a resistive heater's equivalent energy.
Oddly enough (but not really that odd) it seems to be affordable to a lot of people who jet around the globe to tell each-other and the media that people need to fly less, for the climate. It used to be for the environment but that trope seems to be worn out.
We have about 10,000 times as much space as we need for a pure-solar economy at current power use, 1,000 times what we need if we raise everyone to the power use of the average American, but still better than 100 times what we need if we want to do that while having a 10% efficient storage system because most energy is used while the sun is up anyway.
> Most energy used has still an high negative impact on the atmosphere.
Yup, and will do until it’s renewable. If it was already renewable, using that power to make more renewables has no impact whatsoever.
> Low efficiency somewhere is energy potentially wasted that could reduce carbon emissions somewhere else.
Sure, but the ideal is a global superconducting grid, and even if you do that the easy way [0] we’re a long way from the necessary industrial base to get it done.
This option is sufficiently good to be interesting in the meantime.
[0] a ballistic superconductor, specifically a charged non-conductive ring in orbit.
Second best option: a few square meter cross section HVDC cable encircling the planet, which needs quite a big investment in mining to get the materials for but has the advantage we can get most of it done gradually just by continuously upgrading existing grids until the very last step of crossing the Atlantic and/or Pacific.
You mean the electrolysis efficiency? There are examples of up to 70% on the lab, but it was never economically important to optimize it.
Liquids, especially when used in ICE engines later on, would result in an energy efficiency of 5-10% max. This is abysmal and we could use that otherwise wasted energy to decarbonize many other things by directly electrifying them.
It is hilarious how many people think the problem is with reversing the CO2 creation. No, it's a matter of getting the joules to sustain the modern lifestyle and the population count.
Seems relevant
1) Assume a 1x1m solar panel generates 150W at peak.
2) It won't manage that all the time, far from it. Lets say it generates 300Wh per sq. meter. per day, or 110kWh/m^2/year.
To achieve 80000TWh we'd need about 730million 1x1m panels. For comparison, google says the land area of New York city is 783million m2.
Of course it's not just solar, throw in geothermal, tidal and wind too
I think that your statement does not rebutt the parent comment : producing the energy required to sustain our modern lifestyle and population count will have significant impacts on the ecosystems, whatever the source we use for that energy.
Assuming that you still want oceans to work, about 2/3rds of that is not available, which get us to 500x. You also want land-based plants to work, which gets us to <250x and much of the remainder is unsuitable, so let's call it <100x.
"make equipment" through end-use solar is <20%, so we're down to <20x.
What else am I missing?
Even if it is only 10% efficient, some form of carbon capture is going to be required to hit carbon zero. This is one of the most promising mechanisms for carbon capture.
Carbon-hydrogen bonds are an relatively efficient and safe way of storing energy and we have well-developed technology and infrastructure in place to take advantage of that.
water is an easy elemental source of hydrogen. If it is possible to fuel this electrolysis via cheaply obtained renewable energy, then it makes a lot of sense to produce fossil fuels using this method - it will allow the existing infrastructure to consume such produced fuels, so you save capital and energy on replacing them.
Problem is, if you use it for cooling, it's strictly better to use the electricity directly (chances are the sun is shining when it's hot).
And if you use it for heating (at least from day to night), the round-trip efficiency is probably still better for batteries, or electric heating + hot water storage, because you can use heat pumps which are say, 5x more efficient than burning fuel.
If you have an stationary application you will never use something like that. (Except maybe for long time storage, I don't think this will win over long time storage, but it isn't settled.)
One could imagine battery boosters jettisoned after supporting the climb to cruising altitude which autonomously return as drones to the airport.
Carbon hydrogen bonds are one of the best ways to store energy that we have.
A Tesla battery pack is good for about 300 miles. If that's equivalent to 3 gallons of gas, that's saying that Teslas would get 100mpg.
I can believe 40-45 mpg, but 100 requires some evidence.
They are rated for 134 combined MPGe. That is not that crazy for an EV, the ford Mach E gets 93:
https://www.fueleconomy.gov/feg/Find.do?action=sbs&id=43602
Electric drivetrains are really efficient, which is why EV's are practical at all.
Sorry but this goes against the definition in elemental form (in this case it's H2).
Also there is no such thing as `cheaply obtained renewable energy`. If it was your electricity bill would be 0.
Batteries aren't great for super-cold areas. Pure hydrogen, my understanding is that it's pretty much impossible to make a 'leak free' tank. So for things like backup power generation there is an additional challenge. More thinking about need to top off than risks, I'm not qualified to speak to whether such a tank would be a risk.
[1] https://link.springer.com/article/10.1007/s42154-020-00096-z
It's always cheaper to use oil from the ground than it is to use another power source to manufacture oil.
They could be internalized by CO2 pricing, such as CO2 tax or certificates
The "create the useful hydrocarbon out of atmospheric carbon" step needs to necessarily be cheaper than getting dead dinosaurs to a refinery and refining them.
Screeching about externalities adds nothing to the discussion. Burning synthetic hydrocarbon fuel would also release carbon. A CO2 tax would hit it just as hard as it hits traditional hydrocarbon fuels unless you do stupid "craft the tax to pick and choose winners" crap that a carbon tax is explicitly supposed to avoid.
Either way, planting trees appears to be a good mechanism for carbon capture. So go do that instead!
Hopefully we’ll have a huge innovation in batteries, but oil is very energy dense and some burning seems likely for a long time. We also will probably want to reduce CO2 levels from wherever we peak, even assuming we’re not burning any more oil, so carbon capture is important for that too.
Now some of that carbon capture can be in the form of well managed trees, but they take up a lot of land and you have to chop them down and store the wood somewhere that it won’t break down, and that becomes its own storage problem.
As a result, I don't think this can ever make logical sense under any circumstances, very similar to carbon capture attached to fossil fuel generators. It just doesn't pencil out, even in theory.
Basically, gasoline isn't a particularly good fuel unless society is letting you dump the pollution for free, in which case it still isn't particularly good, but some other sucker is paying the price for it. And that other sucker is often you.
Synthetic hydrocarbons will probably remain the only option for carbon-neutral long-distance travel in the foreseeable future.
https://research.noaa.gov/article/ArtMID/587/ArticleID/2667/...
but tomorrow, in that we expect a lot of growth in aviation. That might not be the case, why take a lover for a weekend to Paris when you can go to Montréal? A nuclear powered aircraft carrier could synthesize jet fuel from the ocean and atmosphere and even if it is $15 a gallon it is a bargain -- so the US Military sponsors this kind of research.
The best case for carbon capture now is this technology
https://en.wikipedia.org/wiki/Bioenergy_with_carbon_capture_...
applied to sugar cane alcohol factories in Brazil. You can catch CO2 from fermentation and not have to separate it from N2, compress to 1500 psi and inject into a saline aquifer. Those bioenergy plants are much better than bioenergy plants in the US by any economic or environmental metric. They'd have to get paid something per ton of CO2 captured to make it worth it. This industry is located close to populated areas such as São Paulo and does no harm to rainforests that Brazil must also protect.
Another case is the petrochemical industry in the southern US where CO2 streams are abundant and could be aggregated for scalable saline injection.
Any sort of space manufacturing will require a "circular economy" for carbon (it's precious) and whatever passes for a "petrochemical factory" will produce CO2 and that needs to have energy put into it into some form that can be put back into the "head end", methane would be great. The unique opportunity there is very high temperature chemistry with 24-7 sunlight concentrated with metallized plastic membranes made from the produce of the "petrochemical factory".
I'm also fairly sure electrical flight will be a thing long before we get to the last 3.5% of fossil fuel use anywhere on earth. Gasoline isn't magic, it's just something that we had a lot of lying around and didn't punish people for polluting and killing people with it, because the people with access to it became politically influential. That's it's only unique advantage, which thankfully seems to finally be fading.
How long ago were EVs totally impossible because of the amazing energy density of gasoline? Like 5 years maybe, and now that's laughable. EVs are clearly better. Did gasoline get suddently less energy dense in that period or was that always just BS supported by nothing more than status quo bias?
In vehicles, energy density is not terribly important. The issue has always been the price of the cells. Only very recently they started becoming cost competitive compared to ICE powered vehicles.
The situation is very different in airplanes. At takeoff, something like 40% of the total mass of an airliner is just fuel. The best Li-ion cells have something like 50 times lower energy density than kerosine. It is simply not possible to fly any useful distance with such a low energy density.
And he literally wrote a book published in 2015 on the topic of energy density.
So I'm glad it's obvious now with 20/20 hindsight, but it seems a lot of people can be wrong about this stuff and have their opinions promoted.
Aviation is 30-40 years behind in fuels (they still use leaded gas.). The kind of Fischer-Tropsch chemistry that these guys are messing with has been basically abandoned for automotive use but is still being pursued for jet fuel because they are afraid to use any fuel which isn’t identical to existing fuels in composition…
Traditionally these processes start with a stream of hydrogen and carbon monoxide which can be made from coal or methane, the economics are gawdawful because the reactions that build up hydrocarbons and break them down have to be closely balanced —- polyethylene formation can be explosive, methane forms quickly if the temperature is too high. What it means is you have a big machine (high capital cost) that makes just a trickle of fuel. In the green era people like these guys are mixing up the chemistry so you can put CO2 in instead.
I have been thinking about how you would make plastic membranes from asteroid materials, we think some asteroids have something that is basically coal and the head end would turn that into ‘petrochemicals’ and might have a lot in common with fuel synthesizers… A lot of chemical processes will create waste CO2 which is precious in that context and has to be recycled.
In small aeroplanes yes, I don't think Jet-A has lead in though.
There's no lead in jet fuel, and I'm just not exactly sure what you mean by aviation being "behind" in fuels in that respect. What's the leading edge supposed to be, in gas turbine technology, other than essentially kerosene?
If you want to make carbon neutral jet fuel based on biomass or direct captured CO2 on the other hand, kero is terribly hard to synthesize. Back in the bad old days politically isolated countries such as Nazi Germany and apartheid South Africa built expensive factories to make gasoline and diesel from coal using the same kind of chemistry that the authors of that paper are using.
Even then the economics were so bad it was an act of desperation and nobody would be attempting to synthesize hydrocarbons for ground transportation today because we have batteries, fuel cells, methane, alcohol and other fuels that can be bio based or synthesized more easily.
The Jet A problem is different from the leaded avgas problem but it comes from the same root that if your engine stalls out because of a fuel problem (say water separates out, freezes, clogs your fuel lines and all the engines fail) you have to hurry and find a place to land pretty quick, whereas if it happens to your car it is not so bad. There’s that any and also an unwillingness to make aviators upgrade their hardware (look at the 5G vs altimeters fight.)
I agree that simple fuels makes more sense to synthesize. Methane is simple, but way more difficult to handle than gasoline. 1-butanol and other liquids would be great, but it is not so easy to produce in scale yet, I believe.
Methane-based planes might have a lower TCO if the industry made the switch but the switch would be hard.