Miners earn money by creating new Bitcoins, but the computing power needed to do it consumes large amounts of energy.
They audit Bitcoin transactions in exchange for an opportunity to acquire the digital currency.
Global mining requires enormous computing power, which in turn uses huge amounts of electricity, and consequently contributes significantly to global emissions.
The CBECI, which is produced by the Cambridge Centre for Alternative Finance, tracks the geographic distribution of computing power used for mining Bitcoin – receiving data from a number of commercial Bitcoin mining pools.
The latest data, which covers the four months to the end of August, suggests that most Bitcoin mining (35.4%) is now US based, with Kazakhstan (18.1%) second and Russia (11%) third.