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A simple switch in the coding behind the way bitcoin transactions are verified could cut power consumption by bitcoin mining to near zero, ending one of the main controversies over the virtual currency, according to a campaign launched on Tuesday.

Change the Code Not the Climate says bitcoin’s “proof of work” verification, which requires the use of massive computer arrays to validate and secure transactions, should be ditched in favor of etherium’s “proof of stake” model, where miners pledge their coins to verify transactions; adding inaccurate information leads to penalties, the Guardian reports.

Proof of work is a way of checking that a miner has solved the extremely complex cryptographic puzzles needed to add to the bitcoin ledger.

With the value and use of cryptocurrencies rising, the campaign’s organizers argue bitcoin must follow suit or find another, less energy intensive, method. “This is a big problem. In part because of where the industry stands now but also because of our concerns about its growth,” said Michael Brune, campaign director and former executive director of Sierra Club.

The US now leads the world in cryptocurrency mining after China launched a crackdown on mining and trading last May, reports the Guardian newspaper in London.

“Coal plants which were dormant or slated to be closed are now being revived and solely dedicated to bitcoin mining. Gas plants, which in many cases were increasingly economically uncompetitive, are also now being dedicated to bitcoin mining. We are seeing this all across the country,” Brune said. “There’s no way we can reach our climate goals if we are reviving fossil fuel plants.

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“Boutique wind or solar operations powering a few high- profile mining operations” would not do enough to counter the environmental cost, Brune said. “Fossil fuel growth is outpacing renewable growth in bitcoin mining and that’s the fundamental challenge.”

Even recent moves by energy extraction companies like ExxonMobil, to generate power for mining operations with gas that would otherwise be flared off, release vast amounts of carbon.

Without a change to the code, the fundamental problem will remain that bitcoin’s code “incentivizes maximum energy use”, said Chris Larsen, founder and executive chairman of crypto company Ripple and a climate activist. “The minute that there is the opportunity to go to something dirty, which is what you are seeing, that is going to happen.”

One “nightmare scenario”, he said, is that the world does get to a renewable future in China, the US and EU but countries rich in fossil fuel switch to bitcoin mining to keep their operations running.

“Imagine the Saudis sitting on all that oil, which has a cost of about ½ cent per kilowatt hour – no renewable can match that,” Larsen said. “Bitcoin mining could be this endless monetization engine for fossil fuels. That would be a nightmare.”