I quit thinking about this energy source after re-opening my chemistry book.
You need ~400M-500M tons of steel to make 2-3 Terawatt Hours of Electricity
Disclaimer: My family owns a steel plant, so I'm bias in that I think the carbon emissions required to produce steel wind turbines don't make sense/don't match the intention of building wind turbines.
Where does that "~400M-500M tons of steel" number come from?
The turbines tend to have composite blades and steel towers. Actual studies put the amount of energy returned by wind turbines at ~18 times the energy invested: http://www.theoildrum.com/node/1863
And if not wind turbines, then what is your preferred low-carbon energy source?
Any sort of libertarian or free-market approach to this problem will likely fail. This is one of those mission critically deal breakers where human behavior can't be modulated in a desired direction.
"the aggregate installed wind power of about 2.5 terawatts would require roughly 450 million metric tons [of steel]"
That's terawatts (nameplate power capacity) NOT terawatt-hours! A very important distinction since the steel is a onetime cost for the life of the turbine and can potentially be recycled at EOL.
Yes, you need currently available usually fossil energy to make renewable sources, including PV and nuclear. What is the alternative? Yes, embodied energy / EROEI is important, but it has to be considered fairly across all technologies. Including battery storage and nuclear plants, and the replacement of petrol vehicles with EVs.
You need ~400M-500M tons of steel to make 2-3 Terawatt Hours of Electricity
Disclaimer: My family owns a steel plant, so I'm bias in that I think the carbon emissions required to produce steel wind turbines don't make sense/don't match the intention of building wind turbines.