Climate and environmental groups are calling for an end to tax credits for the carbon capture and sequestration industry, describing the subsidies as wasteful.

In a Monday letter to Congressional leaders led by Food and Water Watch and signed by dozens of groups across the U.S., advocates called said the carbon sequestration tax credit program, known as 45Q, “waste billions in taxpayer money, endanger public safety, and prop up a fundamentally flawed and unreliable technology.”

Supporters of the technology say carbon capture and sequestration is needed to store industrial greenhouse gas emissions deep underground, keeping them out of the atmosphere to avoid warming the climate.

But the technology has not been proven economically viable on a large scale, especially without the 45Q subsidies, which have mostly gone to fossil fuel companies. Companies can also use the subsidies for enhanced oil recovery, which involves forcing carbon dioxide into partially depleted oil field to squeeze out more oil.

The letter cited a 2020 Treasury Inspector General for Tax Administration report that found “widespread fraud and abuse in the 45Q program, with nearly $1 billion claimed for unverified or non-existent carbon sequestration.”