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Carbon-Capture Startup Using Dirt Cheap Material Raises $53 Million

Heirloom uses cheap and widely available limestone to suck carbon from the air. The latest funds will help build its first pilot-scale facility

Piles of limestone at a warehouse in Brazil.

Piles of limestone at a warehouse in Brazil.

Photographer: Dado Galdieri/Bloomberg

A California-based startup has found a way to use limestone — a cheap and widely available material — to remove carbon dioxide directly from the air, potentially overcoming a major hurdle in scaling up the technology needed to avoid catastrophic global warming. 

Heirloom Carbon Technologies Inc. said Thursday it raised $53 million from investors including Breakthrough Energy Ventures, a clean-technology fund led by Bill Gates, and the Microsoft Climate Innovation Fund.