The newest study on bitcoin's energy consumption estimates that about 22 megatons in CO2 emissions are generated per year, Wired reports; approximately equivalent to the carbon footprint of Jordan, Sri Lanka, or Kansas City. When other cryptocurrencies beyond bitcoin are taken into the equation, the figure doubles.
The biggest issue is the use of coal and other "dirty energies" in bitcoin mining. According to the paper's author, an energy researcher at the Technical University of Munich Christian Stoll, “Coal is fueling Bitcoin. The question is how to prevent it, and that’s up to local regulators.”
Until now, it has been difficult to get reliable or consistent estimates on mining's environmental impact. There was limited information regarding the miners in use, their location, and the fuel used to feed them. While one study suggested that bitcoin mining could lead to a 2°C increase in global temperatures, others claimed those figures were way off due to the use of renewable energies.
Stoll managed to get more specific data after three major Chinese mining chip makers disclosed information when filing for initial public offerings. That made “technical details and data about market share” available to the public for the first time, which Stoll’s team used to estimate bitcoin's carbon footprint. Although the estimates are lower than some groups predicted, Stoll suggested regulators in key mining regions take mining's emissions into consideration and to act accordingly.