If we have a large supply of very cheap energy, say from fusion or feeding a black hole, then a CO2 to jet fuel to CO2 cycle can be considered the same kind of thing as charging and discharging a battery. And it would be similarly "net zero" for CO2.
Exactly. It's not "making fuel" in the sense that would be energy positive. It's using CO₂ as feedstock into an energy conversion process that transforms energy otherwise obtained into a form usable in jet engines.
I hope these misleading "turned into" style of headlines go away when energy input is required. Carbon + Hydrogen + Oxygen + energy + information can be "turned into" pretty much any organic substance.
The sibling comment from jeffbee is essentially correct, depending on which part of the "petroleum infrastructure" you're referring to in your comment: the price of extracting and burning fossil hydrocarbon fuels does not reflect the cost of their externalities, primarily climate change driven by CO2 emissions.
However, you are right in the sense that taking advantage of our current hydrocarbon distribution infrastructure would save capital costs versus switching to, e.g., an all-hydrogen or all-electric energy infrastructure. The trick is to get those hydrocarbons from non-fossil sources, which is a solved problem from a technical perspective but very much still unsolved from an economic perspective.
The German government recently updated its estimate for the societal costs of putting a ton of CO2 into the atmosphere to 195 euros (up from 180 euros a few years ago).
If you pay the energy price you can upgrade it to almost anything you want. But that is the question, how many joules of energy do I need (end-to-end) to spend to store one joule in a synthesized hydrocarbon.
Is the heat given off by burning fossil fuels significant compared to the amount of heat trapped by the released CO2 over it's lifetime in the atmosphere?
The advance described in the paper in question could turn out to have a fairly significant impact on the economics of an air-to-fuels process that includes it.
For context: the paper describes an air-to-fuels system requires carbon dioxide as a carbon source as well as some source of hydrogen gas. Given these two feedstocks there are then two main routes to fuel production: reduction of carbon dioxide to methanol or ethanol, which can then be "upgraded" to heavier fuels, or reduction of carbon dioxide to carbon monoxide, which is used along with the hydrogen to feed a Fischer-Tropsch reaction producing a variety of fuels directly. My understanding is that in either case production costs are dominated by the cost of acquiring the feedstocks, which are in turn mainly driven by the cost of energy.
What the article describes is a technique that modifies the Fischer-Tropsch step of the process that uses it, which would perhaps bring costs down somewhat for that step. Additionally, and more importantly, carbon monoxide is not needed as a separate feedstock as CO2 is apparently directly reduced by this new catalyst - this is where significant cost savings could potentially realized.
I'm no expert in any of this but for what it's worth I did go through a process of estimating what "air-to-fuels" fuel might cost to produce and came up with a cost of about $1300 per metric ton. If the technique described in the paper were applied to the process I investigated, the $1300/mt price could potentially decrease to around $1000/mt. For comparison, Brent crude oil is currently about $380/mt and aviation fuel is about $430/mt.
The example in the article of colocating with a coal plant is bonkers. Seems like coal gasification would be more efficient than turning coal into electricity and carbon and then trying to turn the carbon into liquid fuels.
This is a valuable technique but only if we have a lot of spare clean electrical power to do it with.
I'd rather CO2 be turned into a building material... like wood or bricks. That way it's fixated. Sorta defeats the purpose to put it back out into the atmosphere, and why I don't really see today's "carbon capture" stuff going anywhere unless we find a source of "free" energy.
It depends on your comparison point. If the comparison point is "we're going to fly all these airplanes; with what shall we fuel them?" it makes a lot more sense than if you start with "we have a lot of excess energy and want to remove carbon dioxide from the atmosphere; where shall we put it?"
Ah so what you're saying is it's like flying an airplane with a nuclear plant, but the nuclear plant is on the ground and hooked up to a hydrocarbon plant as an intermediary.
Simple question: will it take less energy to do the conversion than you get out the other end? Will the process itself generate less carbon than the existing process? All these “net zero” claims never mention how the rest of the system is affected. Eg, zero emission electric cars: where I live, our electricity comes from coal power plants.
1) The conversion will always be energy-negative due to the laws of thermodynamics, as a sibling comment mentioned. This is true even of existing fossil fuels, though we tend not to think of it that way.
2) The process of converting CO2 to hydrocarbon fuels leads to a decrease in atmospheric carbon. Burning these fuels or fossil fuels (what I assume you mean by "the existing process") produces an increase in atmospheric carbon.
This means it's possible to create a net-positive, net-neutral, or net-negative outcome with respect to atmospheric CO2 concentration depending on how you balance these two processes.
As you point out, "zero emission" doesn't mean the same thing as "no net CO2 release"; rather, it more often means "zero emissions of CO2 at the point of energy usage," with CO2 emissions usually occurring elsewhere. That said, with a system of hydrocarbon fuel production from air-captured CO2 it is genuinely possible to have "zero emission" mean "zero net emission of CO2 over the entire energy transport process."
EDIT: The key enabling technology is, of course, carbon-free renewable energy, of which solar is likely to represent the lions' share as time passes.
Obviously not (laws of thermodynamics), but if we ever get eg a profitable fusion reactor going, it'll be a huge deal to be able to do this - because existing petroleum-fuel stock will still need to run.
If fusion power ever works it could be a useful base load source to replace coal and fission. But fusion is unlikely to ever be cost competitive with solar and wind, so I expect those sources to be used for synthesizing liquid fuel.
Agreed; this kind of thing seems like a more attractive target for unused peak capacity of renewables. But it only makes sense if the capital costs are low enough that the economics still work even if it's only run part time. Which is a pretty high bar.
Methane doesn't seem very practical for an airplane, storing the pressurized gas in tanks seems heavy. Would you store liquid methane? Liquid methane and liquid oxygen are used as rocket propellants, not sure if that makes sense for an airplane compared to conventional liquid (at ambient temperature/pressure) fuels.
You're correct: methane would not work well as a replacement for conventional aviation fuel both for the reason you mention (weight of storage system) as well as the lower energy density per unit volume: 35 MJ/L for jet fuel vs. 9 MJ/L for compressed natural gas at 3600 PSI. (https://en.wikipedia.org/wiki/Energy_density)
kg matters a lot, of course, but most airplanes are out of space for additional tankage as currently designed. (They are designed for a given mount of fuel capacity volume, in relation to the mass of that fuel volume. None would have a 4x multiple.)
Scaling volumetric storage by a factor of four produces about 2.5x the wetted frontal area (4 ^ (2/3))
If I understand correctly LNG is 20MJ/L so not a 4x difference (but much colder, with all that implies...)
I would agree there’s a likely range reduction, but I don’t have any stats on current normal fueling as a percent of max capacity (iow: are there many routes that are running more than half full today?)
Liquid actually makes a lot of sense for airplanes. You can even use simple styrofoam insulation, as the consumption rates would still exceed the evaporation rates. The drawback is that if for some reason the plane can't fly but has fuel, it would have to be bled off to not build pressure.
One of the reasons liquid methane works well as a rocket propellant is that rockets need to carry their own oxidizer with them. Because methane is a smaller molecule, less oxygen is required to oxidize a given amount of methane.
With an airplane, which gets its oxidizer from the atmosphere, methane's lower oxidizer requirement is basically irrelevant.
The amount of oxidizer on a molar basis shouldn't depend on the size of the molecule, just the number of C and H atoms that need to be oxidized to carbon dioxide and water, respectively. Some molecules (ex. ethanol) also have some oxygen already in them which reduces oxidizer needed but also reduces the energy density of the fuel (its basically partially burned already).
You don't. You take yesterday's CO2 from the atmosphere, turn it into today's fuel, and emit it as tomorrow's CO2 into the atmosphere. Then repeat the cycle continuously.
If you were successful in capturing the CO2 from the jet and taking it to the point of landing, the airplane would get (much!) heavier as it flew rather than lighter.
The article says that by adding heat to raw materials such as carbon dioxide and some catalyst they can produce jet fuel. Which can be burned to produce carbon dioxide and more heat.
I'm glad to know that according to this article's author they have invented a perpetual motion machine that generates free energy.
I would however, prefer to read an article by someone who understands basic thermodynamics and feels like explaining this to an audience who is assumed to also understand basic thermodynamics. Presumably there is an input of energy (other than heat) which is the most significant part of generating jet fuel -- but unless I overlooked something, the article doesn't mention it.
It is using the fuel as a battery. Will still take more energy in than you get by burning, but it is better to do that from solar than digging it out of the ground
If we have a large supply of very cheap energy, say from fusion or feeding a black hole, then a CO2 to jet fuel to CO2 cycle can be considered the same kind of thing as charging and discharging a battery. And it would be similarly "net zero" for CO2.