Woodland Carbon Units

A Woodland Carbon Unit (WCU) represents one tonne of CO2e (carbon dioxide equivalent) that has been removed from the atmosphere by the growing trees. A WCU’s forerunner, a Pending Issuance Unit (PIU), represents a ‘promise to deliver’ a Woodland Carbon Unit during a given period.

Legally Backed and Certifiable Woodland Carbon Units

The Project Design Document, the carbon calculator and the additionality test (see the previous section) are all necessary precursors to validating your woodlands under the Woodland Carbon Code.

This occurs just after planting and is undertaken by a third-party auditor who checks that the details submitted in the calculator match the reality on site. If the scheme passes the auditors inspection, it is “validated” and the corresponding volume of Pending Issuance Units (PIUs) can be registered in the IHS Markit Registry.

Woodland Carbon Units

A Woodland Carbon Unit (WCU) represents one tonne of CO2 which has actually been sequestered. A PIU is therefore commuted into a WCU when the woodland has undergone another inspection.

This is known as verification and involves the third-party auditor verifying that the woodland has grown as was originally expected so that the predicted volume of CO2 has been sequestered.

Confirmation, that the sequestration is actual, as opposed to pending, allows companies use WCUs to offset current emissions, as opposed to PIUs which can only counter-balance future emissions.

Pending Issuance Units

PIUs are the forerunners of Woodland Carbon Units.

One PIU represents the anticipated (or “pending”) sequestration of one tonne of carbon dioxide. They are registered to a woodland while it grows and sucks up the corresponding tonne of CO2.

They are certified when a woodland is validated and can be sold to companies to offset their future emissions.

Who Buys Woodland Carbon Units?

Greenhouse gas reporting is mandatory for all large UK companies i.e. those with annual sales above £25.9mn or balance sheet assets above £12mn. There are approximately 12,000 such companies

The Woodland Carbon Code offers them the ability to:

  • EITHER purchase PIUs as part of their long-term plans for neutralising their carbon emissions.
  • OR buy WCUs which will compensate for their immediate emissions.

Companies who are planning to compensate for their emissions and achieve ‘net zero’ can buy PIUs as part of the long-term strategy for achieving carbon neutrality. Alternatively, they can buy verified WCUs which will offset their current emissions.

Assessment & Certification


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Pending Issuance Unit: A promise to deliver a Woodland Carbon Unit during a given period, based on the trees’ predicted growth Woodland Carbon Unit: A ton of carbon dioxide which has been sequestered in a scheme verified under the Woodland Carbon Code