I have a little bit of experience in energy...
Our energy issues are divided into two problems
1) How to generate what we need. This is easy, after you account for coal and methane (natural gas) we probably have enough fossile fuels for hundreds of years. In the long term nuclear actually works great, the french (of all people) have a terrific nuclear program. Theirs is better than ours not because of technology, but because of management. Fortunately the NRC has seen the light on that, and our next generation of nuclear plants should less problematic. Throw in a few renewable sources, and we really are in pretty good shape here.
2) How to deliver it in useable form where we need it. This is where it gets complicated...
-Almost every point of energey consumption in our industrial society is technically flexible as to how it is delivered. Cars and trucks can use batteries or alternative fuels, trains can use electric, and large ships can burn almost anything (including peanut butter).
-The one major point of consumption that has essentially NO flexibility is, you guessed it, large commercial aircraft:
Kerosene has a fairly unique combination of low weight, high density, high energy/mass ratio, low volatility, and ease of handling. There simply is no obvious substitute.
To make matters worse, airplanes and their engines are designed for kerosene, and due to the inherently tight integration of aircraft systems, it would be essentially impossible to modify (and then certify) an existing airplane for another fuel source. You would have to build NEW airplanes from scratch $$$$$$.
Even if you build new airplanes, you will take a huge hit on performance due to the relatively poor energy energy/mass/density relationship of non-kerosene fuels. Some of these fuels, and why they suck for airplanes:
Gasoline: Also petroleum based, very volatile.
Methanol/Ethanol: Low energy density. A 747 would barely have enough range to do PHX - LAX. Trans-oceanic flights would be out of the question.
Methane: Low energy density, requires either high-pressure or cryogenic tanks.
Hydrogen: EXTREMELY corrosive, volatile, explosive, and cryogenic. It is easy to make from tap water though. Very good energy/weight ratio (think space shuttle), very poor energy density (imagine a space shuttle external tank attached to your airliner)
Batteries: Ridiculous. The technology needs to improve by a factor of 1000 to even think about it. And after you spend all that money on batteries, you still have to buy electricity to charge them.
Nuclear: Required shielding is too heavy(yes this has been tried
)
The only really practical solution for airliners as we know them is to find an economical and practical industrial process to make kerosene out of coal, methane, or raw carbon and hydrogen. This can be done in the laboratory now, it just needs to be scaled up (a lot)... Othewise our airliners will be replaced by blimps and bullet trains in 70 years or so.