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Bitcoin has been criticized for the amount of electricity consumed by mining.As of 2022, the Cambridge Centre for Alternative Finance (CCAF) estimates that bitcoin consumes 131 TWh annually, representing 0.29% of the world's energy production and ranking bitcoin mining between Ukraine and Egypt in terms of electricity consumption.Until 2021, according to the CCAF much of bitcoin mining was done in China. Chinese miners used to rely on cheap coal power in Xinjiang in late autumn, winter and spring, and then migrate to regions with overcapacities in low-cost hydropower, like Sichuan, between May and October. In June 2021 China banned Bitcoin mining and Chinese miners moved to other countries such as the US and Kazakhstan.As of September 2021, according to the New York Times, Bitcoin's use of renewables range from 40% to 75%. According to the Bitcoin Mining Council and based on a survey of 32% of the current global bitcoin network, 56% of bitcoin mining came from renewable resources in Q2 2021.The development of intermittent renewable energy sources, such as wind power and solar power, is challenging because they cause instability in the electrical grid. Several papers concluded that these renewable power stations could use the surplus energy to mine Bitcoin and thereby reduce curtailment, hedge electricity price risk, stabilize the grid, increase the profitability of renewable energy infrastructure, and therefore accelerate transition to sustainable energy and decrease Bitcoin's carbon footprint.Concerns about bitcoin's environmental impact relate bitcoin's energy consumption to carbon emissions. The difficulty of translating the energy consumption into carbon emissions lies in the decentralized nature of bitcoin impeding the localization of miners to examine the electricity mix used. The results of recent studies analyzing bitcoin's carbon footprint vary. A 2018 study published in Nature Climate Change by Mora et al. claimed that bitcoin "could alone produce enough CO2 emissions to push warming above 2 °C within less than three decades." However, three other studies also published in Nature Climate Change later dismissed this analysis on account of its poor methodology and false assumptions with one study concluding: "[T]he scenarios used by Mora et al are fundamentally flawed and should not be taken seriously by the public, researchers, or policymakers." According to studies published in Joule and American Chemical Society in 2019, bitcoin's annual energy consumption results in annual carbon emission ranging from 17 to 22.9 MtCO2 which is comparable to the level of emissions of countries as Jordan and Sri Lanka or Kansas City. George Kamiya, writing for the International Energy Agency, says that "predictions about bitcoin consuming the entire world's electricity" are sensational, but that the area "requires careful monitoring and rigorous analysis". One study done by Michael Novogratz's Galaxy Digital claimed that Bitcoin mining used less energy than the traditional banking system.
