I believe the argument is explained in the linked post by about slide 7. You simply didn't read enough. The author is not arguing that transaction volume and "work" are directly related, but rather that for the entire system to function meaningfully, mining "work" is required to secure the chain and in order for the miners to be meaningfully rewarded, a speculative market of transactions is required (the author does not agree with you that miner's are meaningfully rewarded by Bitcoins, he argues they require fiat, again see slides 1-7). So by his argument if you stopped 90% of transactions you will see a commensurate drop in mining, because the miners won't do it without reward.

This is part of a larger argument that these requirements drive the system towards centralization, thereby defeating all the work to decentralize. These are not my arguments, but they seemed to be reasonably well presented by someone who understands the mechanics of proof of work.

You're final argument that other chains may rob Bitcoin of incentives to mine may well be additional vulnerabilities of the network, I don't know.

>we keep having articles saying that bitcoin transactions are a waste of energy, and everyone ignoring that the block reward halves every few years until it drops to zero, so it not built with the incentives to use this much energy forever.

Bitcoin transactions aren't a waste of energy, a high bitcoin valuation is an incentive to "waste" energy (commit resources to mining).

The block rewards will drop over time, but they're denominated in BTC, so it's hard to predict what the incentive to mine will be.

It will be a long time before block rewards reach zero.

But not such a long time before block rewards are dominated by transaction fees, a few decades at most (in two decades, the block subsidy will be 32x smaller).

> and everyone ignoring that the block reward halves every few years until it drops to zero

It's not the reward that drops to zero, but only the block subsidy. Thus the reward will largely (eventually entirely) consist of transaction fees. Which means your first observation

> The energy usage does not come from processing transactions; it is largely independent

becomes increasingly wrong over time.

So which part of those 2 statements you quoted is false? Sure, the energy of usage of Bitcoin is not directly used to process transactions, but it still part of the Bitcoin system.

It is strange language to say 'carbon footprint is used' but I see no interpretation where the statement is correct. The 'carbon footprint' is actually 'used' to secure the network, motivated by how the process generates more bitcoin. The size of the carbon footprint is not caused by, nor dependent on, that 90% of transaction volume. It doesn't make sense even when I try to find the most forgiving interpretation. There's an implication that the data means the transactions are enormously wasteful but it doesnt logically follow.

The block reward dropping doesn't mean that the value of the block reward drops though, does it? If the value of bitcoin goes up then the value of the block reward can increase even though the amount of bitcoin in the reward decreases.

The block reward consists of two parts, the ever-halving block subsidy, and the transaction fees.

I wonder if anyone has modeled what the energy usage is AFTER all the mining is done?

It's a complete unknown and entirely open field of inquiry.

It's like asking about what types of books will be published in a 100 years from now, given we just invented the Gutenberg press.

In short, it will depend entirely upon the demand. This whole thing is about money, technology is secondary.

Presumably high transaction fees to offset the loss of direct reward for mining to keep the engine of PoW running so the network remains secure.

That's what is required for the network to remain secure, but there is no direct mechanism to cause that to happen. You can observe all the other blockchains with weak security as experiments: there is nothing preventing the security from just dropping to the point where it is easy to perform 51% attacks.

Absolutely but even as someone who is very much against crypto it’s such a massive hole that threatens miners directly I can’t see it going unaddressed. Or the whole thing collapses which suits me just fine.

It sounds like just a nitpick to me. The networks exists to process transactions. It's only fair to count its total energy consumptions to see how efficient it is. That it does a lot empty work without processing anything is a by product of a bad design. If it's mainly about minting new coins and once it's done the energy usage goes down then we could just skip the step, you know?