https://www.truthcoin.info/blog/pow-cheapest/
"Nothing is Cheaper than Proof of Work"
on | 04 Aug 2015
Just to belabor this a bit, the paper demonstrates that the mining market will tend to expend resources equivalent to miner reward. It does not prove that mining work has to expend *energy* as a primary cost.
Some might argue that energy expenditure has negative externalities and that we should move to other resources. I would argue that the negative externalities will go away soon because of the move to renewables, so the point is likely moot.