Quote Originally Posted by Gelatinous Cube
Unless I'm missing something, none of the alternatives will pay off enough to repay the energy expended in extracting them.
Wrong.

Nuklear power - Already the cheapest source of energy available.

Biodiesel/ethanol - More expensive than oil products, but will rather soon have a commercially viable price when oil prices goes up and the volumes of alternatives goes up.

Solar power - Still limitations in the usage, but already its viable for smaller need of electricity as well as heat.

Wind power - Well, here you have a point. Still hard to get economy in to it.

Hydro power - Already establised. Limitations due to locations.

Garbage disposal - Turning garbage and spill in to energy is something that has economy in areas where you can combine it. Very possible alternative for cities and densely populated areas.

Just to mention a few...