I was thinking that too, initially.
It's relatively cheap to make liquid nitrogen (it cost roughly $1/gal delivered in large quantities a few years ago), and that's much colder than dry ice. I don't know the process, but it would seem that dry ice should be cheaper than LN2.
Trouble is, when you're talking about extracting millions or billions of tons, the cost gets very high very quickly. Maybe that chemical process is cheaper on that huge scale.
Of course, just extracting it isn't good enough. You need to find a cheap way to get it out of the atmospheric cycle and (ideally) return it to a rock-like state so it stops trapping infrared radiation.
It'll be interesting to see how things turn out.
Cheers,
Scott.
Trouble is, when you're talking about extracting millions or billions of tons, the cost gets very high very quickly. Maybe that chemical process is cheaper on that huge scale.
Of course, just extracting it isn't good enough. You need to find a cheap way to get it out of the atmospheric cycle and (ideally) return it to a rock-like state so it stops trapping infrared radiation.
It'll be interesting to see how things turn out.
Cheers,
Scott.