>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...