0.6% is not a very large amount. Also, the proportion of renewable sources in electricity production is growing with every passing year. Why no one is talking about the environmental footprint of minting coins and printing banknotes? How much ecological damage is done by the mining of metals that are being used to mint coins? Also, how much forest is cut down every year, for printing banknotes? Once mined, Bitcoin is indestructible. On the other hand, banknotes and coins need to be replaced time to time.
Including for this reason, I do not see any serious fears of obtaining energy to mine bitcoins. Nowadays solar panel production technologies are getting cheaper every day. The construction of power plants is very beneficial even for individuals on the roofs of houses and it can completely solve the problem of cheap clean energy. The sun can still be considered an inexhaustible source of such energy.