3.3 Project carbon sequestration
- Project developers shall use the relevant template WCC Carbon Calculation Spreadsheet (Standard or Small Project tab) to predict the project carbon sequestration.
- Emissions resulting from the preparation of a site prior to planting, shall be calculated and subtracted from the project carbon sequestration at year 1. This includes losses of carbon through removal of vegetation (trees or other biomass) or disturbance of the soil.
- Carbon sequestration in woodland biomass shall be restricted to the long-term average carbon stock that is projected to accumulate on the site.
The prediction of project carbon sequestration is checked at validation. It may be re-assessed at verification if there are changes to the management or growth rate/health of trees.
Project carbon sequestration is the changes in carbon stocks due to woodland creation over the project duration as a direct result of the project.
This page outlines how to predict changes to carbon stocks that will occur over the duration of the project. The monitoring section explains how to assess actual carbon stocks later on in the project once the trees are growing and carbon has been sequestered.
Project developers should bear in mind when agreeing to sell PIUs that the tools here provide a prediction of the carbon that is likely to be sequestered, and not a guarantee that a particular woodland will sequester a certain amount.
Projects should account for project carbon sequestration using the WCC Carbon Calculation Spreadsheet V2.4 March 2021 (xlsx) following the associated guidance (pdf). The calculator includes the following:
- Emissions from establishment activities, ongoing management and clearfell.
- Emissions from soil disturbance
- Sequestration in tree biomass, litter and deadwood (and in a limited number of scenarios, soil)
SMALL PROJECTS (5 hectares net planting or less): Can use the 'Small Project Carbon Calculator' which is simpler to complete, and conservative. Projects using this prediction tool can use the less intensive Basic Monitoring' from year 15 onwards.
STANDARD PROJECTS: Should use the 'Standard Project Carbon Calculator'.
Soil Carbon and the Woodland Carbon Code sets out the methodology for Organomineral and Mineral soils. The WCC Carbon Calculator includes assumptions about the likely soil disturbance and soil GHG emissions. Alternatively, projects can make a soil carbon assessment prior to tree planting with repeat assessments as the project progresses.
Soil carbon accumulation can currently only be claimed for projects on a mineral soil where the previous landuse was arable or rotational grass and the woodland will be managed as minimum intervention. This is included within the WCC Carbon Calculator.
- Tree biomass: During 2022/3, the data behind the WCC Carbon Calculator is being reviewed and revised to incorporate new growth and yield models and to refine estimates of contributions from root and branch biomass. The revised estimates for some tree species may be more conservative than current predictions, particularly for the early growth period of broadleaved species. The WCC Carbon Calculator already subtracts 20% from modelled predictions and it is anticipated that these revisions will fall within this threshold.
- Tree biomass: We will develop our Carbon Calculator to include a wider selection of spacings, and to account for the carbon stored in roots and stumps when clearfelling.
- Non-tree biomass: We will publish estimates of the carbon stock of other types of non-tree vegetation.
- Soil. There will be a number of developments:
- We will update the soil carbon methodology using results of ongoing research. This will allow us to say with more certainty both the amount of soil carbon lost on woodland establishment as well as the rate of accumulation of soil carbon as the woodland grows and matures.
- We will establish a soil carbon assessment protocol to enable projects to consistently assess the soil carbon content of their soil.
- Ongoing research will help us better understand the changes to soil carbon due to woodland creation and management.