OGCR-Smart-Contracts

Smart contracts for the OGCR digital carbon registry (DCR). Each token carries a snapshot of a registry record plus a link back to it (_url / _uri) and an integrity hash (_hash, keccak256 of the registry's response body).

The tokenizer mints these tokens from registry records; the chain cache mirrors them back into the registry.

Token family

ParcelNFT ──────────────┐
                        ▼
                   ActivityNFT ◀── CertificationNFT   (one per certificate; a
                        ▲                              re-certification adds one)
                        │
            CarbonCreditBatchNFT ── owns ──▶ token-bound account (ERC-6551)
                                                   │ holds
                                                   ▼
                                             CarbonCredit (ERC-20)

Contract	Standard	One token per	Minted when
ParcelNFT	ERC-721	parcel_id	parcel_owner_verification is verified
ActivityNFT	ERC-721	activity_id	activity_verification is verified and a certificate_of_compliance exists
CertificationNFT	ERC-721	certificate_of_compliance_id	a certificate_of_compliance is created, including each re-certification
CarbonCreditBatchNFT	ERC-721 + ERC-6551	carbon_credit_batch_id	an activity_monitoring_period_verification carries a value for a benefit field
CarbonCredit	ERC-20	—	minted into a batch's token-bound account, amount of the batch
CarbonERC6551Registry, CarbonERC6551Account	ERC-6551	—	infrastructure for the batch accounts

Every token contract has an owner (can change the minter) and a single minter (the tokenizer's key). mint takes the recipient and the token's data struct.

Fields

ParcelNFT — parcel_id, parcel_uri, parcel_hash.

ActivityNFT — activity_id, operator_id, operator_name, name, summary, website, activity_type, unit_types, city, country_id, certification_scheme_id, parcel_ids[], start_date, end_date, activity_url, activity_hash.

CertificationNFT — certificate_of_compliance_id, certificate_of_compliance_uri/hash, activity_id, activity_nft_id, activity_uri/hash, activity_name, certification_scheme_name, certification_scheme_uri/hash, certification_body_name, certification_body_uri/hash, country_id, issue_date, expiry_date, audit_report_uri/hash, carbon_removals_under_baseline, soil_emissions_under_baseline, permanent_net_carbon_removal_benefit, carbon_farming_temporary_net_carbon_removal_benefit, carbon_farming_net_soil_emission_reduction_benefit, carbon_storage_temporary_net_carbon_removal_benefit, unit_types, certification_status.

The quantities are decimal strings exactly as recorded on the certificate (tonnes CO2e). An empty string means the certificate carries no value for that quantity, and tokenURI leaves it out.

CarbonCreditBatchNFT — carbon_credit_batch_id, batch_name, activity_id, activity_nft_id, activity_name, activity_url/hash, country_id, operator_url/hash, certificate_of_compliance_uri/hash, unit_type, monitoring_period_start_date, monitoring_period_end_date, amount, status_code, issue_date, expiry_date, certification_scheme_url/hash, certification_body_url/hash.

amount is the number of units issued for the batch, fixed at mint, in CarbonCredit base units (18 decimals): 6.5 tonnes is 6500000000000000000. The live balance is the token-bound account's CarbonCredit.balanceOf.

Benefit field on the verification	batch_name	unit_type
permanent_net_carbon_removal_benefit	Permanent Removals Carbon Credit Batch	Permanent Removal
carbon_farming_temporary_net_carbon_removal_benefit	Carbon Farming Removals Carbon Credit Batch	Carbon Farming Sequestration
carbon_farming_net_soil_emission_reduction_benefit	Soil Emissions Reductions Carbon Credit Batch	Soil Emission Reduction
carbon_storage_temporary_net_carbon_removal_benefit	Carbon Storage in Product Carbon Credit Batch	Carbon Storage in Product

CarbonCredit — besides ERC-20, mintedTo(address) is the cumulative amount ever minted to an address. The tokenizer funds a batch against that, not against the balance, so credits the owner has moved out are never issued a second time.

Build and test

# Install Foundry
curl -L https://foundry.paradigm.xyz | bash
foundryup

forge build
forge test

Deploy

PRIVATE_KEY=0x... \
MINTER_ADDRESS=0x...            `# the tokenizer's address; default: the deployer` \
PARCEL_CONTRACT_ADDRESS=0x...   `# optional: keep an already deployed ParcelNFT` \
forge script script/DeployTokenSystem.s.sol \
  --rpc-url $RPC_URL --broadcast --legacy

It writes every address to deployments/token-system-<chain id>.env, in the variable names the tokenizer and the chain cache read.

Token data is fixed in each contract's storage layout, so a change to a token's fields means a new deployment of that contract; tokens minted on the previous one stay where they are.

Local chain

anvil --chain-id 2025
forge script script/local/DeployLocalStack.s.sol \
  --rpc-url http://127.0.0.1:8545 --broadcast --legacy

Deploys the whole family and mints one coherent set of records (two parcels, an activity, a certificate, two credit batches with their credits). Addresses go to deployments/local-anvil.env. The chain cache's integration tests run against this fixture.

Reading a token

cast call $ACTIVITY_CONTRACT_ADDRESS "tokenIdByActivityId(string)(uint256)" "<activity_id>" --rpc-url $RPC_URL
cast call $ACTIVITY_CONTRACT_ADDRESS "tokenURI(uint256)(string)" 1 --rpc-url $RPC_URL
# → data:application/json;base64,... (base64-decode to read name + attributes)

Lookups by business key: ParcelNFT.tokenIdByParcelId, ActivityNFT.tokenIdByActivityId, CertificationNFT.tokenIdByComplianceId, CarbonCreditBatchNFT.tokenIdByBatchId. Each returns 0 for an id that has not been minted.

Links

• ERC6551 Standard - Token Bound Accounts
• OpenZeppelin - Smart contract framework