Greenpeace USA – an environmental advocacy group – is calling out Bitcoin for having what it calls an “outdated and efficient” code system. 

In a tweet on Thursday, the organization doubled down on claims that Bitcoin’s proof of work mechanism is contributing to the climate crisis. Instead, it suggested that the code be swapped out for a less energy-intensive mechanism like proof of stake. 

Campaigning Against Mining

The advocacy group’s statements were in response to Ethereum’s successful Merge on Thursday – an event that transitioned the protocol from proof of work to proof of stake. 

“Ethereum just proved that cryptocurrency doesn’t have to come at the cost of a livable planet,” said the non-profit. Meanwhile, it criticized Bitcoin for continuing to consume more electricity than “entire countries.”

Bitcoin’s energy consumption can fluctuate as market conditions change, but has generally risen over time as the Bitcoin mining industry expands. According to the Cambridge Bitcoin Electricity Consumption Index, Its theoretical upper bound consumption is roughly 159.63 TW/h right now. By comparison, the entire country of Norway consumes about 124 TW/h, per data from Forbes last year. 

Its energy footprint comes down to proof of work – a mechanism for achieving blockchain consensus and security by consuming energy. Specifically, users (miners) consume energy in a race to build Bitcoin’s next block, where winners are rewarded with BTC. Naturally, as Bitcoin’s price rises over time, they are incentivized to burn more energy to earn additional rewards. 

As Greenpeace explained, this process is incentivizing miners to bring old coal and gas plants “back to life”, thereby “fueling the climate crisis.”

“It doesn’t have to be this way,” argued the non-profit. “Ethereum – one of Bitcoin’s top competitors — just changed its code system to reduce its energy usage by 99.95%.”

Greenpeace last targeted Bitcoin in March, after Ripple co-founder Chris Larsen funded a $5 million campaign to see Bitcoin transition to proof of stake. Like last time, Greenpeace has also called on Bitcoin-affiliated tech billionaires – Jack Dorsey and Elon Musk included – to spread awareness about its energy footprint. 

Arguments for Proof of Work

Yet Bitcoiners aren’t budging. Dorsey, for one, made clear his distaste for proof of stake protocols after sharing a blog post extolling the superiority of proof of work on Wednesday. 

Dorsey also co-signed a pro-proof of work letter to the Environmental Protection Agency in May, which criticized proof of stake for being prone to centralization. 

MicroStrategy’s Executive Chairman Michael Saylor has also stopped pulling punches in his defense of Bitcoin mining. 

“[Bitcoin’s carbon emissions] would hardly be noticed if it were not for the competitive guerrilla marketing activities of other crypto promoters & lobbyists that seek to focus negative attention on Proof of Work mining,” he said in a letter on Wednesday.

There’s also a question of how much global emissions would fall if the transition actually took place. Bitcoin is estimated to be responsible for about 0.08% of global emissions right now, which would presumably be the limit of its emissions reduction. 

Furthermore, the Merge has demonstrated that not all miners will go offline after such an upgrade. Rather, many appear to have migrated to other proof of work chains, such as Ethereum Classic.