The Bitcoin wiki has a number of counter-arguments https://en.bitcoin.it/wiki/Myths#Bitcoin_mining_is_a_waste_of_energy_and_harmful_for_ecology https://en.bitco

The Bitcoin wiki has a number of counter-arguments https://en.bitcoin.it/wiki/Myths#Bitcoin_mining_is_a_waste_of_energy_and_harmful_for_ecology https://en.bitcoin.it/wiki/Myths#Bitcoin_mining_is_a_waste_o... The future for ethereum is proof-of-stake. This project is called Casper and will be in Ethereum 2.0. For Bitcoin most transactions will be off-loaded to layer-2 networks but PoW will remain on the main chain.