Bitcoin miners are putting as much CO2 into the atmosphere as the entire city of London for the benefit of "almost no one".
Bitcoin, the world’s biggest and best-known cryptocurrency, has fallen 26 percent from the year's high.
All digital coins combined have a market cap of around $1.7 trillion.
Musk has backed bitcoin, a digital currency estimated to cause more pollution than a small country every year.
"He's gone off the rails."
Elon Musk's Tesla car company has invested US$1.5 billion in Bitcoin and plans to accept it as payment.
The digital currency almost almost quadrupled in value during 2020.
Bitcoin reached it's three-year high of US$19,666 earlier this week before crashing.