Sampling is critical to issuing Enhanced Weathering credits because measurements from soil and porewater are needed to verify carbon removal. Isometric works with suppliers to ensure their sampling program meets the protocol. The amount of samples needed is flexible and varies by project.

For sampling to be compliant under the protocol:

• Measurements taken in control and treatment plots should accurately represent a project
• Chemical analysis should be used in control and treatment plots

No other protocols give clear guidance like this on the type of sampling needed to verify carbon removal via enhanced weathering.

Direct measurements are needed to ensure Enhanced Weathering removes carbon because existing models are not yet robust enough.

Measurements required under the protocol include:

• Direct measurements over the full project area
• Allocating 2.5% of the project area for both treatment and control plots

Other protocols allow certification with fewer measurements and rely more heavily on models.

Soil chemistry is extremely complex, meaning it can be difficult to confirm that Enhanced Weathering removed carbon dioxide from the atmosphere.

To verify removal, the protocol requires:

• A statistically significant signal that demonstrates the weathering process took place, with a minimum 95% confidence threshold
• Cross validation of weathering signal (from soil and aqueous measurements)

Statistical significance ensures robust quantification and avoids over-certifying. Other protocols do not specify statistical significance thresholds.