Directly converting CO2 into a gasoline fuel (2017)
nature.com
nature.com
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..)
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.)
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.
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.
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.
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
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?
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.
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
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.
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
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.
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.
You mean the electrolysis efficiency? There are examples of up to 70% on the lab, but it was never economically important to optimize it.
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
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.
Can anyone spot how efficient it is? It declares that it's "Highly efficient", but then no details on what the actual efficiency is.
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.
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.
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.
In small aeroplanes yes, I don't think Jet-A has lead in though.
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.
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.
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.