Bitcoin mining consumed enough electricity last year to release carbon emissions on a par with Estonia, according to a study that suggests the climate change impact of the cryptocurrency isn’t as bad as previously thought.
Past research has suggested that the emissions from mining bitcoin – where computing power is used to solve mathematical problems to create new currency – may be as high as 63 megatonnes of CO2 per year. Some researchers have even claimed the cryptocurrency alone could bust global climate goals.
Susanne Köhler and Massimo Pizzol at Aalborg University in Denmark found that earlier estimates had made blanket assumptions that carbon emissions from electricity generation were uniform across China, where they estimate just over half of all bitcoin mining takes place.
But breaking down the emissions within China to a more regional level produced a much lower global footprint for the crytpocurrency, of 17.29 megatonnes of CO2 in 2018. While coal-heavy Inner Mongolia accounted for just 12.3 per cent of bitcoin mining, it resulted in more than a quarter of the total emissions. The reverse effect was seen in the hydropower-rich Chinese province of Sichuan.
China accounts for 47 per cent of Bitcoin's carbon emissions
Percentage contribution to Bitcoin mining's carbon footprint by location
The researchers also found that it is overwhelmingly the electricity use of bitcoin mining that contributes to the cryptocurrency’s carbon emissions, not the production and disposal of the computers doing the mining, which accounted for just 1 per cent of the emissions.
Köhler says the findings don’t mean we can stop worrying about bitcoin – especially given electricity use per new bitcoin is growing – but we should put it in perspective. “On the one hand we have these alarmist voices saying we won’t hit the Paris agreement because of bitcoin only. But on the other hand there are a lot of voices from the bitcoin community saying that most of the mining is done with green energy and that it’s not high impact,” she says.
Getting a better handle on bitcoin’s carbon footprint will remain tricky until we have more accurate data on where mining takes place – information which Köhler and Pizzol say is scarce today.
Camilo Mora at the University of Hawaii, who wasn’t involved in the work, says the results show the need for more transparency on the location and equipment used in bitcoin mining. Even though the new estimate of the cryptocurrency’s climate contribution is smaller, he says it is hard to believe the impacts from mining are trivial, given many countries, including China, are considering regulating the activity because of its large electricity consumption.
Journal reference: Environmental Science and Technology, DOI: 10.1021/acs.est.9b05687