Quick TakeEthereum, the second-largest crypto by market capitalization, currently uses a Proof-of-Work consensus mechanism similar to BitcoinThis means that the same concerns raised previously about Bitcoin mining are also relatively applicable to Ethereum mining, albeit to a lesser extentEthereum is migrating to a Proof-of-Stake consensus model which is supposed to use 99.95% less energy than the current Proof-of-Work modelThere are many other protocols with different consensus models that are significantly more energy-efficient than Bitcoin and Ethereum today, though they have other trade-offsCrypto and blockchain can possibly lead the way to a sustainable development of technology