[thorn]

Found this interesting comparison of gasoline:

When you fill up your car you are transferring about as much energy as a 747 jet engine could provide in the same amount of time. Here's why:

One gallon of gasoline has about 130,000,000 joules (130 megajoules) of chemical potential energy.

If your car holds 20 gallons then that means the potential energy in your tank is 20 times 130MJ or 2600 MJ. If you filled your tank in 4 minutes (240 sec), then the power (rate of energy transfer) flowing through the gas hose into your gas tank was 2600 MJ/240 sec, or 10.8 megawatts.
For simplicity let's just say about 10MW.

This means that if your car ran on a perfect battery and you could go to an electric filling station and charge your battery in 4 minutes, it would take a 10MW electric generator to provide this much power. Just how big of a generator is that? (by the way, you would need some very large cables).

Well, a power level of 10MW is equivalent to about 13500 horsepower.
A Boeing 747 loaded at 700,000 pounds cruising at 530mph develops about 15000 horsepower in each of its four engines. So, if you could somehow capture all the energy produced by a 747 engine in four minutes and put it into your gas tank, the effect would be very similar to filling it with 20 gallons of gasoline. The next time you are in a large jet and it is taking off, look at your watch for four minutes and think about how much energy that is.

http://www.geocities.com/pughscott/Gasoline.html

[Clouseau2]

Isn't a much simpler way of saying this just "A 747 engine burns the equivalent of 20 gallons of gasoline every 4 minutes"?

[Geology_Guy]

I realize that biofuels take land and energy to produce, but I wonder if in the future planes might use ethanol? It provides almost as much energy per gallon as gasoline.

[MicroHydro]

Embraer in Brazil makes a single seat cropduster that runs on ethanol. You can buy one off the assembly line now. It has a little better performance than the AVgas version of the same plane.

It is possible that in the 2030s rich people will be flying around in DC-3 sized planes fueled with ethanol. The rich flew like that in the 1930s.

As far as jets or average people flying, forget it. All aboard the train, and don't forget to bring your bicycle along for the ride.

[panzer]

Junkers made diesel bombers in WWII. It seems biodiesel flight would be possible too.

[MonteQuest]

I realize that biofuels take land and energy to produce, but I wonder if in the future planes might use ethanol? It provides almost as much energy per gallon as gasoline.

Almost as much?

Gasoline 13,500 Wh/Kg
Ethanol 7,850 Wh/Kg

[OldSprocket]

I realize that biofuels take land and energy to produce, but I wonder if in the future planes might use ethanol? It provides almost as much energy per gallon as gasoline.

Almost as much?

Gasoline 13,500 Wh/Kg
Ethanol 7,850 Wh/Kg

GeoGuy was comparing volumes, not weights:

Gasoline 9,700 Wh/l
Ethanol 6,100 Wh/l

By volume ethanol roughly two-thirds the energy of gasoline. Still not "almost as much". I suspect that weight matters more for aviation than volume anyway, so MQ's figures for roughly half the energy are more pertinent.