From that perspective, there will be a strong need for various rare earth elements. Leading to an insane amount of pollution. Are there any breakthroughs in rare earth extraction & treatment process?

Rare earth is not "that" rare. Not every rare earth element is equally rare. https://en.wikipedia.org/wiki/Rare-earth_element

Quote: Despite their name, rare-earth elements are – with the exception of the radioactive promethium – relatively plentiful in Earth's crust

From https://en.wikipedia.org/wiki/Neodymium: Although neodymium is classed as a rare earth, it is a fairly common element, no rarer than cobalt, nickel, or copper, and is widely distributed in the Earth's crust.

Good practices and recycling could be very important with regard to costs and environment protection.

There is always progress if progress is financed.

Example: https://www.nextbigfuture.com/2018/11/european-ecoswing-buil...

Quote: A conventional wind generator making 1MW of power will have about one tonne of neodymium in its magnets. The superconductor uses about 1 kilogram of the rare earth gadolinium. It costs just $18.70/kg (£14.50/kg) of gadolinium oxide versus $45.50/kg of neodymium oxide.

I doubt that the rare earth is an important cost factor for such a turbine.

http://www.windustry.org/how_much_do_wind_turbines_cost

Quote: The costs for a utility scale wind turbine range from about $1.3 million to $2.2 million per MW of nameplate capacity installed. Most of the commercial-scale turbines installed today are 2 MW in size and cost roughly $3-$4 million installed.

> From that perspective, there will be a strong need for various rare earth elements. Leading to an insane amount of pollution. Are there any breakthroughs in rare earth extraction & treatment process?

What rare earth elements are you talking about, exactly? I keep hearing about the scarcity of such "rare" elements, but except lithium (which isn't that rare, it's just we haven't invested in the infrastructure), I'm not aware of the lack of any other materials needed for EV cells.

Yeah, there's a lot of nonspecific scaremongering; I think the bottleneck metal at the moment is cobalt, but Tesla and others are working on that. http://www.mining.com/tesla-delivers-bad-news-cobalt-price/

Yes, extraction from "red mud" (a widely available waste product of aluminium extraction): https://kuleuven.sim2.be/wp-content/uploads/2018/02/Rodolfo_...

The resulting pollution level is effectively a cost choice.

You've not explained where all this hydrogen is supposed to come from and get transported.