4. Returning VCUs to Tero Carbon (Detokenization/Retokenization)

This flow is used when a Marketplace user wants to withdraw their VCUs back to their own native Tero Carbon account, or if the Marketplace needs to return unsold inventory.

Marketplace Action:

User initiates withdrawal request on the Marketplace to their Tero Carbon account address.

The Marketplace must first detokenize (burn/destroy) the corresponding quantity of its internal VCU token representation. If operating in kgCO2e, it must detokenize the full amount requested.

Calculate Whole Tonnes: Determine the number of full tCO2e being returned (e.g., floor(total_kgCO2e / 1000)). Any remaining fraction < 1 tCO2e cannot be returned to Tero and must be handled/accounted for within the Marketplace system.

Notification to Tero: The Marketplace calls reportTransaction with operation: Detokenization, specifying:

The quantity of whole tCO2e being returned.

The source issuance ID.

The destination Tero Carbon account ID (unitsAccountDestinationID).

Proof or reference of the internal detokenization/burn (e.g., internal transaction ID).

Tero Action:

Receives notification (202 Accepted).

Admin reviews the request, including the quantity and destination account.

[Webhook] Sends rejection webhook if data is inconsistent or invalid.

If approved:

Tero executes its Retokenization process (using the Rebuild Tero smart contract logic). This reactivates the corresponding native Tero VCU tokens or mints new ones with the original lineage, crediting them to the specified destination Tero Carbon account. The quantity will be the whole tCO2e amount specified in the notification.

Generates a new blockchain record and potentially an NFT certificate for the re-tokenization event, publishing to OpenSea.

Updates its internal registry: decrements the Marketplace custody balance, increments the destination user's balance. Marks the VCUs as active ("Held") again.
Sends notifications (email) to the destination Tero user.

[Webhook] Sends a confirmation webhook to the Marketplace that the detokenization notification was processed successfully and the VCUs were re-tokenized.