that sounds pretty cool.
We never know what will happen with the massive electricity which bitcoin miners consume. Maybe some goverments will put a law, sanction what ever on the mining process to cut the electricity waste.
Than IOTA would be the green coin.
Then the PoS algorithm (proof-of-stake) can be called such a "green" nonvolatile one. We need only any computer with Internet access, on which a synchronized wallet will be launched - this is called the masternode. You earn new coins by confirming transactions on the network.
There can be of course both PoW/PoS or as IOTA own unique PoW.