3. Carbon sequestration

Projects shall describe the original condition of the project site, including details of the vegetation cover, soil type and their carbon content.

For standard projects, project developers shall estimate the baseline or changes in the carbon stock at the site for the duration of the project in the absence of the project activities (i.e. business as usual). 

The following carbon pools shall be included in the baseline scenario:

• Tree biomass (above and below ground)
• Litter and deadwood
• Non-tree biomass (above and below ground)
• Soil

Where the carbon baseline shows significant sequestration (i.e. 5% or more of the project carbon sequestration over the duration of the project), it shall be accounted for in ‘net carbon sequestration’ (section 3.4). Otherwise, the carbon baseline is assumed to be ‘no change over time’.

For site description:

• Appropriate maps, photographs or remotely sensed images to indicate previous land cover.
• Results of field survey for vegetation or soil type.
• Maps for soil type.

For baseline calculations:

• Carbon baseline calculations in project design document.
• More detailed calculations of carbon baseline.

• Confirmation in the project progress report of any changes to the baseline assumptions.
• Updated carbon calculator and further baseline calculations (if required). 
   

What is a baseline scenario?

A baseline scenario is a projection of the changes to carbon on the site over the project duration in the absence of the project (e.g. woodland creation) going ahead. It is the reference scenario from which the impact of the project can be measured.  

Small projects: We assume that the baseline is 'no change in carbon stocks over time'. No assessment is necessary.

Standard projects: It is often the case with standard projects that the baseline will be 'no change in carbon stocks over time' if the project was previously grazed pasture or arable land. It would be unlikely there was any carbon sequestration in these cases and we do not allow projects to claim for the 'reduction in emissions' from stopping the previous land-use. 

Calculating the carbon stock at the start of the project

Refer to any maps, photographs, remotely sensed images or field survey results which confirm the condition of vegetation and soil before woodland creation. This will allow an estimate of the carbon stock onsite prior to the project taking place.

• For tree biomass - Use the survey protocol to  estimate the carbon any trees already onsite contain.
• For litter and deadwood - It is unlikely that this carbon pool or changes to it will be significant.   
• For non-tree biomass – Project developers should reference Natural England's Carbon Storage and Sequestration by Habitat 2021 (NERR094) or contact the Woodland Carbon Code team for further information on estimates of carbon stock of other shrubs and vegetation.
• For soil carbon - Unless the project has undertaken specific soil carbon assessment before tree planting, we will assume that the soil carbon content at the site at the start of the project can be derived from looking at the closest land use type. See Table 1 in Soil Carbon and the Woodland Carbon Code. 

Calculating changes to the baseline scenario over the project duration

The baseline scenario is conservative by accounting for sequestration but not emissions. This means the net carbon sequestration (project sequestration minus baseline) will not be more than the actual sequestration of the ecosystem.  

• For tree biomass. In the baseline scenario, any trees already present on the site will continue to accumulate carbon without the project going ahead and this should be accounted for. This can be done by:

   o  Assessing the density of trees present and their current age

   o  Converting this to an equivalent area of woodland of a given age at a given planting spacing

   o  Using the carbon lookup tables to estimate the likely changes to that stock over time

• For litter and deadwood. It is unlikely that this carbon pool or changes to it will be significant. Projects can assume that, in the baseline scenario, there is no change over time to this carbon pool.
• For non-tree biomass. In the baseline scenario, non-tree biomass could accumulate or it could be in equilibrium over the project duration (in which case no changes over time will be accountable). This depends largely on the type of vegetation present. Crops and established grass can be assumed to be in equilibrium and therefore there will be no change over the project duration in the carbon stock of non-tree biomass. However, other biomass may still be growing and sequestering carbon and projects should account for the change to the carbon stock over the duration of the project. Projects should refer to the IPCC 2003 Good Practice Guide for LULUCF.
• For soil carbon. It is hard to predict what soil carbon changes would have occurred in a given baseline scenario. However, given that gains to soil carbon in the non-wooded baseline scenario are unlikely to be significant (greater than or equal to 5% of the project carbon sequestration over the duration of the project) for sites with with mineral or organomineral soil, projects can assume that there is no change over time to soil carbon in the baseline scenario.

The land manager shall confirm any intention to change or intensify the use of land elsewhere on the holding as a consequence of the woodland creation.

For standard projects, if leakage (land use change/intensification outside the project boundary but within the UK) is proposed, then projects shall carry out an assessment to determine whether this will result in greenhouse gas emissions.

If significant greenhouse gas emissions occur (e.g. 5% or more of the project carbon sequestration over the duration of the project), they shall be quantified for the duration of the project and accounted for in ‘net carbon sequestration’ (see section 3.4). Otherwise, leakage is assumed to be ‘no change over time’.

Carbon pools shall include:

• Tree above and below ground biomass
• Litter and deadwood
• Non-tree above and below ground biomass
• Soil
• Greenhouse gas emissions to manage the land which has changed use

• Statement in project design document of intention by the landowner to replace the previous land use or activity elsewhere.
• Leakage assessment in project design document.
• Map of site and surrounding area with leakage risks highlighted.
• Carbon calculator incorporating further leakage calculations.

• Confirmation in the project progress report of current assessment of level of leakage from the project.
• Updated carbon calculator and further leakage calculations (if required)

Leakage is greenhouse gas emissions outside the project boundary as a result of the project (e.g. displacement of agricultural activities might result in deforestation or intensification of use of non-wooded land elsewhere).

Approach to leakage

Due to the existing legislation in the UK which protects semi-natural habitats, biodiversity and protects against deforestation, the Woodland Carbon Code assumes that in most cases there will be no leakage (i.e. leakage equals zero, no change over time) in woodland creation projects. 

Projects using the small project calculator can assume that there is no leakage.

Standard projects should consider whether the project will result in more intensive use of another area of land elsewhere in the UK. If so, then any significant greenhouse gas emissions through changes in land use or management of the area of land should be accounted for over the project duration (significant is more than 5% of the project carbon sequestration over the duration of the project). Leakage assessments are likely to be project specific. The following guidance should help define the scope of the assessment.

1. Any land use change or intensification within the UK which can be attributed to the project going ahead should be accounted for.
2. Only significant greenhouse gas emissions need to be accounted for in the project's net carbon sequestration. Emissions are considered significant if they amount to more than 5% of the project carbon sequestration over the duration of the project.
3. Projects can refer to the IPCC 2003 Good Practice Guide for Land Use, Land-Use change and Forestry and IPCC 2006 Guidelines for national greenhouse gas inventories for guidance.

Project developers shall use the carbon calculator (standard or small project tab) to predict the project carbon sequestration.

Emissions resulting from the preparation of a site before 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) and 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.

At verification, if any changes to your project mean there is 5% or more reduction to the predicted sequestration of your project over time, the carbon calculator shall be updated. 

At verification, you may update your carbon calculator if changes to your project result in less than a 5% reduction in units or increases. Extra Pending Issuance Units shall not be issued until the next verification if your project receives a ‘red’ rating.

Updated carbon calculators shall include a comparison between the new and old calculation. 

The current version of the carbon calculator shall be used where changes are made.

• Carbon calculator.
• Other evidence to justify growth rates.

• Updated carbon calculator, with comparison of old and new prediction of units by vintage if required.

What is 'project carbon sequestration'?

Project carbon sequestration is the change in carbon stocks due to woodland creation over the project duration as a direct result of the project.

Accounting for project carbon sequestration

Projects should account for project carbon sequestration using the carbon calculator and associated guidance. The calculator includes the following:

• Emissions from establishment activities, ongoing management and clearfell
• Emissions from soil disturbance
• Emission from removal of non-tree above and below ground biomass (at project outset)
• Sequestration in tree biomass, litter and deadwood
• Sequestration in soil (in a limited number of scenarios)

Small projects may use the 'small project carbon calculator'. It is easier to complete and conservative. 

Standard projects should use the 'standard project carbon calculator'.

Vegetation removed at start of project

If any vegetation is removed before the start of the project, this should be accounted for (both tree and non-tree biomass). Projects should use Natural England's Carbon Storage and Sequestration by Habitat or contact us for further information on estimates of the carbon stocks of non-tree biomass. They may also refer to the IPCC 2003 Good Practice Guide for Land Use, Land-Use change and Forestry and the IPCC 2006 Guidelines for national greenhouse gas inventories for guidance on estimating the carbon stock of existing vegetation.

Carbon in the soil

Soil Carbon and the Woodland Carbon Code sets out the code's methodology for organomineral and mineral soils. The carbon calculator includes assumptions about the likely soil disturbance and soil greenhouse gas emissions. 

Soil carbon accumulation may currently only be claimed for projects on a mineral soil where the previous land use was arable and the woodland will be managed as minimum intervention. This is included within the carbon calculator.

When should I update my carbon calculator?

If changes to your project result in a 5% or more reduction in units (based on the carbon calculator you used at the time), you should update the carbon calculator at verification. 

If changes to your project result in less than a 5% reduction in units or increases, you may update your carbon calculator at verification. However, if your project is rated ‘red’, no further Pending Issuance Units will be issued until the next verification. 

The following changes to your project may make it necessary to update your carbon calculator

• Changes in species composition or areas of open ground
• Stocking density (at year 5) or predicted growth rates (from year 15+) not achieved
• Extensive beat-up
• Change to long-term management intentions
• Where the project has suffered a reversal since the previous verification (from year 15+) 

If there is a reduction in units in an updated carbon calculator at verification, Pending Issuance Units will be marked ‘not delivered’. There is no cost to mark Pending Issuance Units ‘not delivered’. However, you should consider how you will compensate any buyers of affected units.

If there is an increase in units in an updated carbon calculator at verification, extra Pending Issuance Units may be issued, unless your project is rated ‘red’. There is a cost to issue new Pending Issuance Units at verification. See registry fees.

Projects shall calculate the net project carbon sequestration within the relevant worksheet (standard project or small project) of the carbon calculator. The calculator estimates the total project carbon sequestration (3.3) adjusted for leakage (3.2) and baseline (3.1).

The predicted number of carbon units by vintage shall be identified according to the project’s verification schedule. These shall be divided into the contribution to the Woodland Carbon Code buffer and the claimable carbon sequestration.

At verification, the monitoring report shall confirm the net carbon sequestered since the project start date and the carbon sequestered in the current vintage/monitoring period. 

If the ‘self-assessment’ option has been used, then no Pending Issuance Units shall be converted to Woodland Carbon Units. They will remain pending until the next third-party verification. See 2.5 Monitoring.

• Carbon calculator.
• Pending Issuance Units by vintage in project design document.

• Confirmation of carbon sequestered to date and carbon sequestered in current vintage from monitoring report.
• Updated carbon calculator, with comparison of old and new prediction of units by vintage, if required.

Net carbon sequestration is the total amount of carbon sequestered by the project which can be converted into carbon units. These are divided between the proportion that will contribute to the shared Woodland Carbon Code buffer and the claimable carbon sequestration which is the amount the project can sell or claim. 

Net carbon sequestration equals the project carbon (3.3) plus leakage (3.2) minus the baseline (3.1).