# FAQs

**What does C3 do?**

C3 is a carbon bridge that enables anyone to bridge their carbon credits on-chain and integrate with the ReFi ecosystem. This is achieved by ensuring each 'tokenised carbon tonne' (i.e. the onchain carbon credit) is backed by one verifiable carbon credit from the legacy system. This protects the integrity of the tokenised carbon tonnes, and enables market participants to reap the benefits that Web3 can bring to the Voluntary Carbon Market. 

**Who can use C3?**

As a permissionless protocol, anyone can use C3. Existing players who have access to carbon credits can bridge their assets on to the blockchain to participate in the onchain markets. Those who wish to secure carbon credits can do so via the C3 website. Those who wish to purchase tokenised carbon tonnes can do so in the C3 [carbon pools](/the-basics/carbon-pools.md). 

**How does C3 protect against double counting?** 

At launch, C3 requires each tokenised carbon tonne to correspond to a specially-retired carbon credit in the legacy system. This process copies the metadata of each retired project onto the blockchain and also creates a unique hash that can be used to identify the retired carbon credit. Each unique hash can only be used once to avoid nefarious actors who may try to game the system.  The immutable nature of Ethereum means that once the tokenised carbon tonnes are on the blockchain, they cannot be changed. 

**What carbon projects are eligible?** 

At launch, any type of verified carbon project can be bridged across to the blockchain. There will be 2 AMM pools that projects can be sold into: 

* **Universal Basic Offset (UBO):** accepting all VCS and GS methodologies for credits issued with a vintage > six years from the current calendar year. 
* **Nature Based Offset (NBO):** Nature-based offset index accepting all VCS and GS methodologies characterized as NCS, including REDD+, IFM, and those with VCS or GS certification utilizing CDM-based forestry methodologies such as AR-AM0014. 


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