No, mining will continue as usual even after the block reward drops to 0. At that point, miners will only receive transaction fees, and not transaction fees + the block reward as they do currently.
The energy spent on block production is something that, in theory, _could_ be regulated so as to reduce or cap the pollution it may create. We already do this with other industries, like banning CFCs from refrigerants. Why not do the same with mining?
But before we can have a serious conversation about this, the folks on this site need to understand that the problem is _using fossil fuels to mine blocks_. It makes no sense to talk about how much electricity a Bitcoin transaction consumes, as if that meant anything. Loading and rendering HN takes more electricity, and no one complains about that.
Even "clean" energy isn't free energy.
We need to consider both the costs on the supply side as well as what's driving the demand side for our energy consumption if we want sustainable systems.
The costs of running both our Internet as well as the Bitcoin blockchain are components of that, and if we aren't considering them, it's a mistake.
The energy costs of the Bitcoin blockchain will become highly significant very quickly if the network continues to grow at the pace that it has to date, even if the work is done by machines relying on energy sources multiple times cleaner than those that currently exist.
If we want to alleviate this, I suspect that we'll have to consider what the underlying social factors are that are driving the demand for such a network.
No one said it was. But some energy sources produce far less pollution than others, and are far safer. Also, everything I'm saying about regulating and taxing pollution from PoW applies to every single energy-intensive industry; PoW just happens to be the particular industry at hand.
> If we want to alleviate this, I suspect that we'll have to consider what the underlying social factors are that are driving the demand for such a network.
This is literally what regulation and taxation could address. If you tax cryptocurrency transactions based on how much pollution their miners create, the problem could fix itself -- miners would then be incentivized to use only clean energy to mine (and prove that they are doing so), since that's the way to stay competitive. Also, because literally every transaction is a public record, a government could (a) require KYC for you to trade crypto -- up to requiring you to register your address(es) -- and (b) send you a tax bill each year for the pollution caused by each block that included one of your transactions. Exchanges operating under its jurisdiction would only let you cash out once you paid that tax.
In addition, suitable regulation could require that no more than X% of a utility's electricity can go towards mining (e.g. only during off-peak hours; only if its excess; etc.).
You said "It makes no sense to talk about how much electricity a Bitcoin transaction consumes, as if that meant anything".
The only way for the amount of consumption to not matter is if there is a free or nearly free energy source.
For what it's worth, I agree with you somewhat that regulation and taxation could help, at least to the extent that such actions are enforceable - my issue is simply with your proposition that it is only the source of the energy that matters and not the amount, when in fact it is both.
Yes, but that's not saying that energy is free. I was saying that the energy used to create a Bitcoin transaction is negligible. It only takes a handful of ECDSA signing and cryptographic hash operations, as well as some serialization operations to produce a transaction. The act of validating a Bitcoin transaction only takes a handful of ECDSA verifying and cryptographic hash operations, as well as some deserialization operations (such as evaluating Bitcoin scripts). Loading HN takes more CPU cycles than this, but as I was saying here and elsewhere, it's quite often the case that people mistakenly believe that the high energy cost of producing a block must also mean that the act of producing and validating a Bitcoin transaction takes a lot of energy. This simply is not the case, per the above.
> my issue is simply with your proposition that it is only the source of the energy that matters and not the amount, when in fact it is both.
We're trying to control pollution, not energy output. They are linked, but we shouldn't penalize low-pollution high-yield power plants (like hydro-electric dams or wind farms).
My proposition considers how to effectively regulate miners (really, any high-energy industry) who can easily pack up operations and move between countries. To me, this means that it makes more sense to apply a universal carbon tax/tariff than it is to try and target individual industries. This is something we can actually get decent data for -- all we need to do is use satellites to monitor how much pollution gets emitted from each country or other political division, and apply a tax/tariff on its goods/services proportional to the pollution emitted per capita. Pollution data is something that already gets tracked; we just need to translate it into tax policy.
Life as we know it doesn't care about which industry creates which pollutant, nor does it care about how many gigawatt-hours we can create. Life as we know it only cares that the environment is not so polluted that it can't keep on living.