Additionality and Permanence: The Two Tests Every Credit Must Pass
Two questions decide whether a carbon credit represents a real and lasting reduction: would it have happened anyway, and will the carbon stay stored?
Additionality
A credit is additional when the emissions reduction would not have happened without the carbon finance it generates. If a forest would have been protected anyway, or a technology would have been installed for other reasons, selling credits for it adds nothing to the atmosphere's outcome.
Methodologies test this in different ways. Some ask whether the project is required by law, some compare it with what is common practice in the sector, and some check whether the credit revenue was needed for the project to go ahead. Good methodologies use more than one test.
Permanence
Permanence asks how long the stored carbon stays out of the atmosphere. Forests are vulnerable to fire, drought, pests, and later logging or land conversion. A tonne of carbon released years after it was credited undoes the claim.
Registries manage this risk in several ways. Many forest methodologies hold a share of credits in a buffer pool, which can be used to replace credits if a reversal occurs. Some require the project to assess its non-permanence risk and to commit to monitoring over a long period.
What to check
Look for a published additionality analysis and the methodology's reasoning for it. For storage projects, check the permanence assessment, the buffer contribution, and the monitoring period. A credit with a short monitoring period or no buffer deserves more scrutiny, especially for forest carbon.