Is Bitcoin bad for the environment?
The BBC's Ros Atkins looks into Bitcoin's affect on the environment after Tesla suspended vehicle purchases using Bitcoin due to climate change concerns.
After CEO Elon Musk's tweet, Bitcoin fell by more than 10% after the tweet, while Tesla shares also dipped.
Tesla's announcement in March that it would accept the crypto-currency was met with an outcry from some environmentalists and investors.
The electric car-maker had in February revealed it had bought $1.5bn (£1bn) of the world's biggest digital currency.