Last year I diaried about a 2010 study done by the NRL that suggested a very similar process was feasible for manufacturing jet fuel at sea, using excess electricity from a dedicated nuclear-powered factory ship. The key to the process is the realization that a liter of seawater contains 140 times as much CO 2 as a liter of air. In seawater, nearly all of the CO 2 is actually in the form of bicarbonate ions, which should make extraction from water fairly straightforward because of the electrical charge they carry.

So it's a pleasant surprise to see that the Navy not only was paying attention to their own research, but they have also moved from theory to practice and have actually manufactured real fuel using a similar process.

One big caveat: obviously, there is no free lunch, and this process requires energy as input. But since it is entirely feasible to use non-fossil energy sources to power the process, the fuel created could be essentially fossil-free (carbon neutral) gasoline. The oceans and atmosphere exchange CO2 readily in massive quantities, so taking it from one place is functionally the same as taking it from the other.

The NRL press release contains this interesting quote:



Using an innovative and proprietary NRL electrolytic cation exchange module (E-CEM), both dissolved and bound CO 2 are removed from seawater at 92 percent efficiency by re-equilibrating carbonate and bicarbonate to CO 2 and simultaneously producing H 2 .

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2(HCO 3 -) --> 2(CO 2 ) + H 2 + O 2 + 2(e-)

I'm not enough of a chemist to know whether there is an energy advantage in creating the hydrogen this way rather than by electrolysis of water -- but I'm betting some Kossack out there can figure it out and post in the comments. If there is, that would be huge.

Cost

In the 2010 study, a cost analysis of a jet fuel-from-seawater factory ship came in at about $6 per gallon. But about half the capital cost was for the ship. so presumably a beached reactor would have been able to manufacture fossil-free jet fuel for roughly half that.