Occidental has been shopping for investors since last year for its Stratos project in Ector County, Texas, the largest project designed to suck up carbon dioxide directly from the air, as it plans about another 100 plants of the kind.

Occidental’s first large-scale DAC facility is a crucial test of economics for a technology that the International Energy Agency says will play a key role in decarbonizing the global industry, but which has been too costly in early test efforts.

BlackRock's investment shows support for Occidental's ambitious plans on DAC, despite Stratos' repeated construction delays and cost increases in the past couple of years.

DAC strips CO2 from the atmosphere to bury underground or for use in making products such as concrete and aviation fuel. Both Occidental and Exxon Mobil Corp estimate DAC could be a multi-trillion market for oil producers by 2050, as scale brings costs down.

“This joint venture demonstrates that direct air capture is becoming an investable technology," Occidental's chief executive, Vicki Hollub, said in a statement Tuesday. "BlackRock’s commitment in Stratos underscores its importance and potential for the world."

Occidental on Tuesday increased project costs to $1.3 billion, the second price increase this year. The project was estimated between $800 million and $1 billion in 2022. Its start-up is planned for 2025, from 2024 previously.

Stratos is designed to capture up to 500,000 tonnes of CO2 per year, with construction works expected to employ more than 1,000 people about 30% complete, Occidental said.

BlackRock has signed a definitive agreement to form a joint venture with Occidental through its subsidiary 1PointFive that will own Stratos.

Berkshire Hathaway, the conglomerate run by billionaire Warren Buffett, has been endorsing Occidental's plans indirectly, by buying shares and increasing its participation in the company. It currently owns a 25.8% stake worth about $14 billion.