What is verified during a mandatory surveillance audit in a high-risk RFNBO supply chain involving CO₂?

The surveillance audit of a high-risk RFNBO supply chain involving CO₂ mainly focuses on traceability, in particular the verification of delivery documents and mass balances. Where relevant, this also includes the mass balance of each dependent collecting point and external storage facility. Where CO₂ is used in RFNBO production, the auditor should additionally verify the origin and eligibility of the CO₂, whether capture, compression and upstream transport emissions have been correctly included in the GHG calculation, and whether any exclusions apply, for example, if credits have already been granted to the CO₂ or the fuel was deliberately combusted to produce CO₂ for capture.

Related question: What is meant by a high-risk supply chain under ISCC EU RFNBOs, and when is a mandatory surveillance audit required?