If electrical energy was cheap but hydrocarbons were expensive, it would be cost-effective to electrolyze water into hydrogen and oxygen. By mass, hydrogen is the most efficient way to store chemical energy. By volume, it's not so efficient, and currently storage is difficult. Still, 200 years from now I think materials technology will have advanced a little.
Another option is nuclear-powered aircraft. (http://en.wikipedia.org/wiki/Nuclear_aircraft)
Yet another pie-in-the-sky option would be to beam power to the airplane (either from satellites or ground stations).
I'm no physicist, but I think I just listed three ways airplanes can exist without hydrocarbons.
* Nuclear has trouble with radiation shielding - not good for passenger planes unless you make enormous planes with a couple of thousand passengers.
* Beaming power is going to cook birds along the route
* If you're going to the trouble of making hydrogen, which is notoriously hard to store, you might as well just make jet fuel instead.
The US Air Force has a goal of qualifying all of their aircraft to fly on biofuels by 2011; they've flown B-52s and other aircraft on 50-100% biofuel mixtures. Currently, most biofuels for aviation use cost several times what petrochemicals cost, but I could definitely see this changing. It's actually pretty easy to get a jet turbine to run on anything, but the difficulty is more with qualifying the entire storage/supply chain to be stable, and stability at temperature extremes. If the Air Force can transition to biofuels, it will be relatively easy for scheduled commercial flights to transition.
Given relatively cheap electricity to input, there are plenty of processes to make liquid hydrocarbon fuels -- algae biodiesel, some forms of intensive agriculture, and CO2 sequestration from the air, as are pointed out in the article. These would be "carbon neutral" in terms of atmospheric CO2 as well.
The only reason not all US Navy ships are nuclear is because you can get better performance for frequently-resupplied, less-than-supercarrier-size vessels with gas turbine engines (literally off-the-shelf jet engines exhausting underwater). The fuel is even the exact same as aviation fuel, so you only need your resupply ships to carry one type of fuel.
So I think energy diversification is the key.
Also, I think nuclear is a great alternative to coal,but for it to be a global option there has to be a lot of stuff done foreign policy wise and in the global security space.
This guy's a physicist? The claim is absurd, unless he's rolling economics into the bucket - especially as he's talking decades or centuries from now.
