Carbon Stock Quantification

INITIAL CARBON STOCK

This step is used to estimate the initial baseline of the Restoration Site.

  1. Land Cover Assessment

    A land cover assessment is performed upon receipt of the Project shapefile. This assessment is performed to distinguish woody from non-woody areas within the Restoration Site. 

    πŸ’‘ Remote sensing models quantifying AGB are solely trained on woody biomass and should not be used to estimate non-woody biomass. To assess carbon stocks accurately, ERS separates woody from non-woody areas and uses different datasets to estimate them.

    1. Woody/Non-woody mask. The Project shapefile is transferred to an AGB Provider to obtain a woody/non-woody biomass mask, a raster format map that distinguishes the location and size of woody areas within the Restoration Site. Refer to Appendix 1 for more details on the AGB provider.
    2. Non-woody areas classification. An analysis is performed to distinguish the different primary classes of the remaining non-woody areas (water, shrubs, grasses, bare soil, crops and buildings). The latest version of the ten-metre ESA WorldCover model is used to classify non-woody areas into specific land cover types (grasslands, shrublands, croplands, bare soils, built-up, and snow). This model harnesses data from Sentinel-1 and Sentinel-2 satellites and employs machine-learning techniques to generate maps with a resolution of ten (10) metres.

  2. Biomass Quantification of Woody and Non-Woody Areas

Separate approaches are then used to estimate AGB for woody and non-woody land cover classes.

    1. Above Ground Biomass.
      1. Woody areas. The AGB Provider generates a Woody AGB map that estimates the AGB at the pixel level in raster format for woody areas. This is referred to as π—”π—šπ—•π—‹π–Ύπ—Œπ—π—. 
      2. Non-woody areas. Various methods are employed to calculate non-woody AGB based on the information provided in the non-woody areas classification (1.2). Non-woody AGB is referred to as π—”π—šπ—•π—‹π–Ύπ—Œπ—π—‡β€“π—.
        • For shrublands, a default ratio of 0.1 is used to convert forest biomass to shrubland biomass according to the AR-TOOL14.
        • For grasslands, a default value for each climate zone is selected, according to the IPCC, as demonstrated in Appendix 2.
        • For bare soils and croplands, the AGB is estimated at 0.
        • Non-forestable areas such as infrastructure and water bodies are excluded from the AGB quantification.
    2. Below Ground Biomass.
      1. Woody areas. The woody BGB is estimated to be a proportion of its AGB as dictated by the root-to-shoot ratio (RS). The relationship between BGB and AGB is represented by the equation (1):

                • Where: 
                  • π—•π—šπ—•π—‹π–Ύπ—Œπ—π— = Woody BGB at the Restoration Site; tDM.
                  • π—”π—šπ—•π—‹π–Ύπ—Œπ—π— = Woody AGB at the Restoration Site; tDM.
                  • 𝖱𝖲𝗐 =Root-to-shoot ratio of woody biomass; dimensionless. The root-to-shoot ratios applied are based on the 2019 updated values from the IPCC, which provides root-to-shoot (RS) values for each ecological zone across continents (Asia, Africa, North and South America), distinguishing between above-ground biomass values less than and greater than 125 tDMΒ·Ha-1. ERS uses values specific to natural origins; dimensionless.
      2. Non-woody areas. For non-woody terrains, the estimation of BGB follows the same equation as for woody areas, guided by the IPCC's root-to-shoot ratio (RS), tailored to the specific climate zone. This approach ensures that the BGB estimation is reflective of the region's ecological and climatic characteristics. Non-woody BGB is obtained using equation (2):

              • Where:
                • π—•π—šπ—•π—‹π–Ύπ—Œπ—π—‡β€“π— = Non-woody BGB at the Restoration Site; tDM.
                • π—”π—šπ—•π—‹π–Ύπ—Œπ—π—‡β€“π— = Non-woody AGB at the Restoration Site; tDM.
                • 𝖱𝖲𝗇–𝗐 = Root-to-shoot ratio of non-woody biomass. A default value is obtained from the IPCC for each climate zone; dimensionless.
      3. For grasslands, the aggregated biomass (AGB and BGB) provided by the IPCC is used. Refer to Appendix 2 for more details.

  1. Total Biomass of the Restoration Site

The aggregated biomass comprises the above and below-ground biomass of the woody and non-woody components within the Restoration Site. The aggregated biomass is obtained using equations (3), (4) and (5):

    • Where:
      • π—•π—‹π–Ύπ—Œπ—π— = Total woody biomass at the Restoration Site; tDM.
      • π—”π—šπ—•π—‹π–Ύπ—Œπ—π— = Woody AGB at the Restoration Site; tDM.
      • π—•π—šπ—•π—‹π–Ύπ—Œπ—π— = Woody BGB at the Restoration Site; tDM.

    • Where:
      • π—•π—‹π–Ύπ—Œπ—π—‡β€“π— = Total non-woody biomass at the Restoration Site; tDM.
      • π—”π—šπ—•π—‹π–Ύπ—Œπ—π—‡β€“π— = Non-woody AGB at the Restoration Site; tDM.
      • π—•π—šπ—•π—‹π–Ύπ—Œπ—π—‡β€“π— = Non-woody BGB at the Restoration Site; tDM.

    • Where: 
      • ππ—‹π–Ύπ—Œπ— = Total biomass at the Restoration Site; tDM.
      • ππ—‹π–Ύπ—Œπ—π— = Total woody biomass at the Restoration Site; tDM.
      • ππ—‹π–Ύπ—Œπ—π—‡β€“π— = Total non-woody biomass at the Restoration Site; tDM.

  1. Biomass Conversion to CO2 Equivalents

Biomass in the Restoration Site is converted into CO2 equivalents (CO2e) to determine its total GHG removals. 

The AR-TOOL14 A/R Methodological tool’s equations are used to translate biomass into carbon content and subsequently into CO2e. This ensures a consistent and standardised measurement aligned with global carbon reporting metrics.

The relation between carbon stock and tree biomass is obtained using equation (6).

    • Where:
      • π—–π—‹π–Ύπ—Œπ— = Carbon stock in the Restoration Site; tCO2e.
      • 4412 = Molecular weight ratio of CO2 to Carbon, which is 4412; dimensionless. 
      • 𝖒π–₯ = Carbon fraction of tree biomass; tCΒ·tDM-1.
      • A default value of 0.47 is adopted.
      • π—•π—‹π–Ύπ—Œπ— = Total biomass at the Restoration Site; tDM.

The initial baseline is determined by the carbon stock (π—–π—‹π–Ύπ—Œπ—) and is expressed in tonnes of CO2e.


FINAL CARBON STOCK

This step estimates the carbon stock of the Reference Site. 

  1. Selection of a Reference Site

    1. ERS requests the selection and adoption of a Reference Ecosystem and geographical coordinates of a physical Reference Site. 
    2. The Project’s Reference Ecosystem is used to inform the restoration objectives.
    3. The Reference Site is used to quantify the GHG removal capacity of the Project. 

Refer to the Reference Ecosystem Guidelines for more information. 

  1. Carbon Stock at Reference Site

    1. Upon submission of the Reference Site’s shapefile, the AGB provider generates: 
      1. A woody/non-woody biomass mask in raster format, showing the distinction between woody and non-woody areas at the Reference Site.
      2. A woody AGB map that estimates the AGB at the pixel level in raster format. 
    2. Woody BGB is obtained using AGB values from step 2.1.2, using equation (7):

    • Where:
      • π—•π—šπ—•π—‹π–Ύπ–Ώπ— = Woody BGB in the Reference site; tDM.
      • π—”π—šπ—•π—‹π–Ύπ–Ώπ— = Woody AGB in the Reference site; tDM.
      • 𝖱𝖲𝗐 = Root-to-shoot ratio,; dimensionless. The root-to-shoot ratios applied are based on the 2019 updated values from the IPCC, which provides root-to-shoot (RS) values for each ecological zone across continents (Asia, Africa, North and South America), distinguishing between above-ground biomass values less than and greater than 125 tDM/Ha. ERS uses values specific to natural origins.

    1. The total biomass of the Reference Site is obtained using equation (8): 

    • Where: 
      • 𝗕𝗋𝖾𝖿  = Total woody biomass at the Reference Site; tDM.
      • π—”π—šπ—•π—‹π–Ύπ–Ώπ— = Woody AGB in the Reference Site; tDM.
      • π—•π—šπ—•π—‹π–Ύπ–Ώπ— = Woody BGB in the Reference Site; tDM.

    1. The conversion to CO2e is obtained using equation (9):

    • Where: 
      • 𝗖𝗋𝖾𝖿= Carbon stock on the Reference Site; tCO2e.
      • 4412 = Molecular weight ratio of CO2 to Carbon, which is 4412; dimensionless.
      • 𝖒π–₯ = Carbon fraction of tree biomass; tCΒ·tDM-1.
      • A default value of 0.47 is used. 
      • 𝗕𝗋𝖾𝖿= Total woody biomass at the Reference Site; tDM.

    1. The average carbon stock in the Reference Site is calculated as an estimate of the carbon stock by size (in hectares). This process enables the utilisation of this data for further processing in the calculation of the Project's GHG removal capacity. The average carbon stock per hectare in the Reference Site is obtained using equation (10): 

    • Where: 
      • 𝗖𝗋𝖾𝖿 = Mean carbon stock on the Reference Site, represents the mean CO2 sequestrated; tCO2eΒ·ha-1.
      • 𝗖𝗋𝖾𝖿 = Carbon stock on the Reference Site; tCO2e.
      • 𝗔𝗋𝖾𝖿 = Area of the Reference Site; ha.

GHG REMOVAL CAPACITY

Using the initial and final carbon stocks, this step estimates the GHG removal capacity of the Restoration Site.


πŸ’‘In this methodology, ERS expects that the Restoration Site will reach carbon stock levels comparable to the Reference Site by the end of the crediting period.


  1. GHG removal capacity of the Restoration Site

The GHG removal capacity of a terrestrial forest restoration Project is determined by calculating the difference between the carbon stock of the Reference Site and the current carbon stock of the Restoration Site. This is obtained using equation (11): 

    • Where: 
      • π—–π—‰π—ˆπ—π–Ύπ—‡π—π—‚π–Ίπ—… = Project's GHG removal capacity; tCO2e.
      • π—”π—‰π—‹π—ˆπ—ƒπ–Ύπ–Όπ— = Size of the Restoration Site; ha.
      • 𝗖𝗋𝖾𝖿 = Mean carbon stock on the Reference Site; tCO2eΒ·ha-1.
      • π—–π—‹π–Ύπ—Œπ— =  Initial baseline of the Restoration Site; tCO2e.
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