You can do proof of work based on random memory access for example rather than pure computation. The monetary cost ends up being identical, but it’s much better for the environment.

>but it’s much better for the environment.

Why? If OPEX is reduced (lower electricity costs), it's logical to assume that it will be replaced with CAPEX, given how competitive mining operations are. If that's the case, that will mean electricity being used to power ASICs being replaced with chemicals required to fab semiconductors (along with electricity for those fabs). It might be better in terms of GHG emissions, it would be a wash for overall environmental impact.

Thinking about environmental issues abstractly aka energy vs chemicals doesn’t give you a basis for comparison. You need to dig into the details. In a green world you’re comparing X square feet of solar panels + Batteries with building RAM and environmentally building more RAM is less damaging.

I haven't heard of this sort of proof of work before. Do you have a reference to it?

If you're referring to memory-hard hashing algorithms, I believe those are just resilient to ASICs/GPUs, but still require significant CPU energy. I'm not convinced those would be better for the environment, so if you're referring to those, do you also have an explanation for why they'd draw relatively less power?

Memory-hard hashing algorithms are basically the same idea.

They use less power simply because people are going to spend the same total amount of money in terms of compute hardware + energy, however RAM consumes less energy per per dollar spent on it than ASICs/CPU’s etc.

3W per 8GB of DDR4 is a reasonable baseline. https://www.crucial.com/support/articles-faq-memory/how-much...

The effort going into proof of work is the effect of Bitcoin's value, not the cause. Due to the difficulty adjustment, the total mining expense adjusts to be a little less than the real value of the reward offered.

It is hoped among Ethereum enthusiasts that moving from Proof of Work to Proof of Stake in Ethereum 2.0 will solve those massive energy usage problems without introducing vulnerabilities into the system.

>without introducing vulnerabilities into the system.

Did they end up solving the "nothing at stake" problem?

Yes. With Ethereum’s PoS system, you get penalized for voting in multiple forks.

See https://eth.wiki/en/concepts/proof-of-stake-faqs (I can’t link to the paragraph).

The "What is the “nothing at stake” problem and how can it be fixed?" proposes 2 solutions. Which one does ethereum use? The page itself is pretty long, and I can't find an answer with a quick skim.