A newly announced “Crypto Climate Accord” aims to erase cryptocurrencies’ legacy of climate pollution. That’s a tall order considering the enormous amounts of energy that the most popular cryptocurrencies — bitcoin and Ethereum — consume. The loose goals laid out in the plan so far face potentially insurmountable challenges.

The “accord” is led by the private sector — not governments — and outlines a few preliminary objectives. It seeks to transition all blockchains to renewable energy by 2030 or sooner. It sets a 2040 target for the crypto industry to reach “net zero” emissions, which would involve reducing pollution and turning to strategies that might be able to suck the industry’s historical carbon dioxide emissions out of the atmosphere.

Lastly and perhaps most realistically, it aims to develop an open-source accounting standard that can be used to consistently measure emissions generated by the crypto industry. They also want to develop software that can verify how much renewable energy a blockchain uses.

If achieved, those goals would solve a very real problem. Bitcoin alone has roughly the same carbon footprint annually as Hong Kong, while Ethereum’s annual carbon emissions rival Lithuania’s. Their climate pollution is growing even as scientists’ research warns that global emissions need to be cut almost in half this decade to avoid the worst effects of climate change.

The accord has support from some influential names in climate action and the crypto industry — including cryptocurrency company Ripple,