Carbon and credits
Methodology
A methodology is the approved rulebook for one type of carbon project. It sets which projects qualify, how the baseline is set, which carbon pools and gases count, what must be monitored, and how the credits are calculated. Every credit traces back to one.
Two projects doing similar work under different methodologies can produce different numbers of credits for the same tonnes, which is why buyers increasingly ask which methodology was used and in which version.
Methodologies are revised over time, often tightened. A project registered under an older version keeps it until renewal.