Signals

Heirloom Carbon

Heirloom Carbon,

315,000 metric tons of carbon from the atmosphere over 10 years. For a sense of scale, that’s equivalent to about 75% of the carbon Microsoft emitted in 2022

$200 million, “based on market prices,” or $635 per ton

The process starts with limestone, which is formed from the detritus of corals, clams, and other sea creatures that use the dissolved carbon and calcium in the ocean to build their shells. Heirloom grinds up limestone and does something that humans have been doing for thousands of years — heats it in a kiln. This loosens carbon dioxide from the rock, leaving behind calcium oxide