Heirloom, a San Francisco–based carbon-capture start-up, has raised $53 million in venture capital funding. The firm uses carbon mineralization, like that found in nature to produce limestone, to capture and store carbon. The company says its technology is more efficient at the “gigaton” scale than other direct-air-capture technologies. Heirloom aims to capture 1 billion metric tons of carbon dioxide by 2035. Investors include Breakthrough Energy Ventures and Microsoft’s Climate Innovation Fund.