Could Carbon Dioxide Be Turned into Jet Fuel?
wired.com
wired.com
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.
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.
I mean, until the reserves are depleted the energy is basically free, we just need to pump it up and refine it.
(Then again, solar power is basically "free", we just need to catch it and store it... so my 2nd paragraph is maybe kind of dumb.)
If you had the renewable energy surplus necessary to do it, you'd make as much liquid hydrocarbon as you could, and pump it back into the ground.
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.
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.
[EDIT] Forgot to include a link to my analysis: https://bit.ly/34JTCFm
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.
Trees are 90-95% air. Carbon, hydrogen, oxygen, nitrogen. Here's Feynman explaining this.[1]
Last one in the e-fuel space I was staring at was: https://doi.org/10.1016/j.joule.2020.01.002 from Rob McGinnis of a startup called Prometheus.
airminers.org lists other startups in this space. I'm still skeptical of it but curious to see what's out there.
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.
Scaling volumetric storage by a factor of four produces about 2.5x the wetted frontal area (4 ^ (2/3))
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?)
With an airplane, which gets its oxidizer from the atmosphere, methane's lower oxidizer requirement is basically irrelevant.
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.
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.