The cryptocurrency’s production generated about as much carbon dioxide over 30 months as 1 million cars in the same period.

It takes approximately the same amount of energy to mine a dollar’s worth of cryptocurrency as it does to mine a dollar’s worth of certain metals.

Cryptocurrencies such as Bitcoin have raised environmental concerns because ‘mining’ virtual coins requires energy-intensive computer calculations. But quantifying the environmental impact of cryptocurrency production is difficult.

Independent researchers Max Krause and Thabet Tolaymat calculated that it takes about 17 megajoules of computer power to generate US$1 in Bitcoin, even when the energy used for peripheral activities, such as cooling computers, is not factored in. By comparison, it takes 5 megajoules to mine US$1 in gold and 7 megajoules to mine an equivalent value of platinum. Aluminium-mining energy requirements, at 122 megajoules, topped the researchers’ list.

Over 30 months from 2016 to 2018, the authors report, Bitcoin mining produced an estimated 3 million to 13 million tonnes of carbon dioxide. That range does not account for mine operation and maintenance; even so, it is roughly equivalent to the range of carbon dioxide produced by about 1 million cars, although it is still less than 0.01% of global emissions.