A type of charcoal first used by Amazonian tribes thousands of years ago is becoming a key component of net-zero goals set by Microsoft, JPMorgan Chase and other blue chip companies eager to offset their carbon emissions.

Known as biochar, this black substance created by heating biomass and other agricultural waste can store carbon for hundreds of years and improve soil quality at the same time. It’s a "true carbon removal solution at scale,” according to Microsoft, and the tech giant along with BlackRock and JPMorgan are among those that have bought biochar credits.

The market for biochar remains small for now, thought it seems poised to soar as more farmers use it as a soil additive and companies seek new ways to meet net-zero targets. Biochar has the potential to sequester up to 2 billion tons of carbon dioxide annually by 2050, or almost as much as India emits in a year.