But at $230 dollars per kilogram, there is bound to be a lot of energy input in its extraction, not to mention a lot of earth moving. Even though it's nearly as abundant as lead, it's not concentrated anywhere, else it would be as cheap as lead.
Everything has "hidden" environmental costs. Even wind power. There's over 1000 tons of concrete in the base of every 1.5 MW wind turbine. Also enough steel to make a locomotive. I wonder how long a wind turbine has to be on line before it pays back the energy debt created by building it.
No form of land transport is more energy efficient than a railroad train, but an airplane doesn't need millions of tons of steel rail, a forest of railroad ties, and bridges connecting the airports. Makes me wonder if it's really more efficient when you take into account everything. There's a reason a train ticket across the U.S. is more expensive than air fare.