[nullifidian]

Gold is something fundamental in this universe -- a chemical element. Bitcoin will become outdated as technology changes, so as a store of value it's inferior long term. Gold is also actually useful in many technological processes.

>The cost of mining gold each year is therefore US$97.6B.

That's not the cost of mining. That's the market cost of gold mined this year.

Also, the presupposition that gold pollutes far more is not backed by any evidence and or reasoning. Fuel used in China to power bitcoin farms had been mined somewhere, with corresponding pollution and other externalities. To compare pollution between these two one has to develop a criteria/scoring system for various forms of pollution, and go through a lot of data.