One startup's method relies on the same natural process that pulls CO2 out of the air to create limestone.
By one estimate, the pledges out there already would require a forest five times the size of India.
The voluntary carbon offsets market is unregulated, with no standard pricing. And offsets may not deliver what they promise.
Cleaner jet fuels and electric planes are still decades away, meaning Delta is focusing on carbon offsets.
The carbon offset market is growing fast.
Landowners would pay to “store” carbon.