If we can use electricity to turn atmospheric CO2 back into jet fuel it could still be net zero emissions. At that point the planes are just using hydrocarbons as a means of dense energy storage.
Technologically-speaking, been done; the economics aren’t quite there yet, but there are some promising noncarbonization paths that potentially could scale to price-parity, depending on global fuel costs.
Going into the future, I think the assumption that one needs to hit exact parity with existing fossil fuels at their current price point will be re-examined. The economic comparison should be conventional extraction fossil fuels + externality costs vs cost of a scaled carbon neutral jet fuel production.
One could already see maybe small scale operations capturing niches - maybe if a corporation that operates a private jet wants to further a reduction in their carbon footprint.
Completely agree that the best and most market-friendly path is to take socialized CO2 costs and apply them to point-of-emission prices — though I doubt entrenched interests of the iron triangle variety will allow that to happen. Nonetheless, if we assume Johnson and Hope (2012)’s range of $55-$266 social cost per ton of CO2, even current capture-and-sequester methods look price-competitive, which is encouraging!
Politically, I wonder if the best solution is the approach the other end of the development cycle, with dynamically scaling investment incentives that expand your "credit limit" to lend more if your projects successfully reduce carbon, but overall scale back as total carbon emissions reduce. Sort of a Green New Deal Fannie Mae type entity. Add in incentives to retire stranded fossil fuel centric assets like fracking rights, etc. This creates a psychologically different environment, more like a Fear of Missing Out on the development rush instead of a Fear of getting a Big Stick regulation.
Sounds like an approach that would coexist nicely alongside technology funding efforts! ARPA-E and EERE have done some great work in that regard; thankfully and a bit surprisingly Congress has so far declined to defund them, despite the Trump administration’s consistent efforts to shut them down, so hopefully they’ll continue to support innovative and incremental advances. Adding carbon incentives to a tax-and-rebate scenario (should we ever get to that) would seem prudent.
I not intimately familiar with ARPA-E and EERE funding programs, but if the follow the common model of selection of funding to a expert tech evaluators, they are a bit different from what I was musing about. They aren't bad, just far too constrained for what we need.
Instead, I'm for transferring funding decisions under the program to a much more open set of actors to originate investment loans (much like mortgage brokers). The investment performances are evaluated on their successes/feasibility, the loans purchased from their originators with high feasibility (i.e. we're scaling known limits), as well as opening up higher origination limits (if they prove out better carbon negative/netural tech). It's more of a financial tooling solution than a tech centered solution. This increases the possibility of failures, but provides a regulated scale out needed with a optimization criteria to keep scaling along successful lines with more organizations rewarded who make successful carbon investments. Experts like ARPA-E could definitely be involved in assessment, but the scale would be completely different then what has gone on before.
The economics are extremely attractive if you have an abundance of electricity production at unpredictable times with build electricity rates tending negative occasionally. Turn that excess electricity into kerosene for jets and ocean travel and turn a profit!
Aviation accounts for 10-13% of transportation [2]. (global data looks similar, although I don't have a link at hand)
So while 2.5% is not nothing, it is only a small fraction of energy consumption and could remain Kerosene based in the medium term.
Also, a lot of flights could theoretically be shifted to high speed rail.
[1] https://en.wikipedia.org/wiki/World_energy_consumption#By_se...
[2] (2016) https://www.eea.europa.eu/data-and-maps/indicators/transport...