| > The bigger problem (IMHO) is going to be certain elements and metals that aren't so easily replaced. I agree with the author that getting certain elements from space is going to be economically tricky (rather than technologically tricky) compared to how cheap it is to pull stuff out of the ground. I don't think this is a real issue. Expensive metals are recycled extremely efficiently even today. This is only going to get easier as we go on. > You can recycle iron to a degree but a certain amount is lost through corrosion/rust. Rare earth elements are harder to replace. Iron is the metal that least needs recycling. There are deposits for essentially unlimited amounts at prices not absurdly higher than the present market conditions. Also, should energy get cheaper, iron would be greatly substituted with aluminium in construction. (And the aluminium supplies of the surface of the earth are essentially infinite.) The talk about REE is largely misguided. REE are not rare. There are exploitable deposits pretty much in every country that's larger than Luxembourg and has exposed rock. The world deposits are greatly larger than any reasonable use we have for them. The reason REE is in the news is that extracting it is an extremely dirty process, and if you want to do it in a first-world country, you have to pay very much to clean up after you. China captured nearly all of the world production not because they have a large share of a limited resource, but because they allowed miners to dump their separation waste in rivers. This makes REE extraction cost a fraction what it would be if you had to rebury all those unwanted heavy metals, and so the Chinese mines so depressed the market price that all the non-subsidized mines elsewhere in the world shut down. As the Chinese started restricting exports (which is only shrewd of them, considering the massive societal cost they bear of the cheap production), the market price rose again and mines elsewhere started to open. The Mountain pass mine is now finally entering large-scale production, and will very soon make the US a net exporter of REE. |