The Voluntary Carbon Standard Association, which launched trading services in November, is finally adding a global registry to its services.

However, a key component of the registry that would allow carbon offsets to be traded across multiple registries has been delayed because of technical problems, Reuters reports.

Traders of carbon offsets have awaited such a system that would provide transparent tracking and trading of Voluntary Carbon Units (VCUs).

David Antonioli, CEO of the association, said the system will enable companies to know their VCUs aren’t being double-sold and make them more tradable.

The system ideally will allow VCUs to be transferred across registries, a feature that might save buyers from having to open accounts in different registries. However, more news on this feature will not be available at least until April 1, Antonioli said.

A criticism of the carbon offset market is that some offsets have been double-traded. Last April, the California Climate Action Registry launched Climate Action Reserve to create voluntary carbon market standards in the United States.

Last fall, Point Carbon put out a paper addressing what it called “significant market confusion regarding the complex relationship between the renewable energy and carbon markets.”