CBLKs, or Changeblocks, are a class of ERC20 assets representing proportional ownership of a pool of CBTs. Specifically, each CBLK represents one tonne’s worth of CBT assets from an underlying pool. There are many possible types of CBLK, depending on the types of CBT comprising the pool. CBLKs offer incredible flexibility when tokenising climate assets: users can select the kinds of assets that best suit their requirements, without losing the ease-of-use and transparency of blockchain assets.

Users will most likely interact with CBLKs, as opposed to CBTs, as they provide exposure to the average value of a collection of climate asset and offer increased liquidity compared to CBTs. Furthermore, the value of a CBLK will be more stable than the values of the individual assets in its underlying CBT pool.

CBLKs always exhibit a 1-to-1 with the tonnage of the credits backing the CBTs, as well as the CBTs themselves. This means that 1 CBLK always maps to 1 tonne, or 1 total CBT, split amongst multiple projects/CBTs.

For example, in the above 'Better Shipping' CBLK, burning 1 CBLK yields the following quantities of CBTs:

  • 0.2 Improved Ship Hull Coatings

  • 0.3 Reduced Shipping Fuel Consumption

  • 0.5 Sonihull Ultrasonic Anti-Fouling Technology


The first, and simpler CBLK is fixedCBLK wherein the composition of underlying CBTs does not change. This means that the types of assets, and their relative quantities can never be changed, including by contract owner.


The other type of CBLK, unfixedCBLK acts more like an index token, allowing the contract owner to rebalance the ratio of underlying CBTs, as well as add or remove assets. The mechanism by which this occurs is somewhat complex and is outlined further in the technical docs.

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