[Sohcahtoa82]

The thing is, it doesn't have to.

Bitcoin (and all other Proof-of-Work cryptos, which is basically all the major ones) only consume tons of power because the incentive to mine creates an arms race where whoever has the most hashing power makes the most money.

Bitcoin could be run on a single computer mining on a 10 year old CPU, but then it would be highly centralized, and decentralization is touted as one of the greatest features of Bitcoin. But with the incentive to run your own miner(s), and make it/them as powerful as you can to get the largest piece of the block reward pie, it ends up being a massive energy sink.

That's why people are pushing for the change to Proof-of-Stake in Ethereum. By taking away the incentive to waste tons of power on mining, it drastically reduces the carbon footprint of it.