I wonder how the environmental impact of mining gold compares to mining bitcoin?

Both are pretty bad.

Gold mining is mostly strip mining tons of ore, spraying it with cyanide, collecting the runoff, and refining that. Then you pack up and leave before someone makes you clean up.

Pollution from Gold mining: https://sciencing.com/types-pollution-generated-gold-mining-...

A very rough estimate: World wide Bitcoin mining operation spends per year around 60% as much electricity as all of USA's bank offices: https://news.ycombinator.com/item?id=15615601

With Bitcoin mining there is a high incentive to actually use renewable energy sources and could be physically outsourced to places where building green power plants is otherwise not practical due to the limits of creating a power grid to make such a power plant profitable.

Maybe it's digital gold.

Maybe when the price stops rising no one feels any desire to buy it anymore and people are left holding worthless numbers.

Yes, maybe it will become digital gold. If it were true digital gold, it would have a similar valuation closer to gold, i.e. $8tn (a 60 fold increase of its current value).

A whole lot of the world's gold is held by governments. For BTC to reach similar valuations, it would need governments to buy it. Why would they?

Pension funds will be buying next year.

I don't know whether governments will buy Bitcoin, but I wouldn't consider it unlikely that some country decides to use crypto as a replacement to their fiat currency -- either the government of a developed nation does it, or the people just decide that their local money isn't worth the paper it's printed on, and decide to use some sort of cryptocurrency.

I know this sounds crazy, and I would've called it a ridiculous notion if someone told me this 5 years ago, but I don't consider it too unlikely anymore. It has grown on me.

Due to quantitative easing, money just isn't worth much anymore and asset prices have gone up a lot across the board. Just look at the recent acquisition of a painting by Leonardo da Vinci: $450m. That could not have happened 20 years ago.

Would a country whose currency isn't worth the paper it's printed on have the infrastructure to use BTC? Would they be able to afford the transaction fees?

BTC would really need the support of a developed government, but those governments aren't eager to give up control of their currency.

Not saying it will be Bitcoin. It could be Ethereum, or some other crypto with (very) low transaction fees.

I don't think Bitcoin is a currency anyway.

Building a crypto banking service that can be controlled through a phone (e.g. in Africa) should have tremendous value given the very high inflation in some countries there.

Like people holding gold in the period when gold does not appreciate are left holding worthless chunks of metal?

Gold doesn't require a worldwide network of specialized computers to continue operating so it will continue to be useful.

The internet needs a worldwide network of specialised computers to continue operating. I bet it won't be very useful anymore once we turn those off.

People use the Internet for a lot more than speculation.

What do people use BTC for other than speculation?

Buying drugs, money laundering, and ransomware

/s?

Gold only requires worldwide network of traders and physically secure holding places and general sense of security so it can change hands.

All that's required to to exchange gold is one person that has gold and another person who wants gold and has something the first wants to trade for it.

Really? Let's meet, I'll give you gold.

Or: for the majority of people, holding hold, recognizing gold, and exchanging gold is not possible. You need experts for that, and they all take commissions. And sometimes scam you.

You don't need experts; you can learn how to identify real gold yourself, in far, far less time than is required to learn to understand a cryptocurrency.