6.4 Quantification

complies with 2.5.6 NCS

Forests are greenhouse gas storages (carbon storages). They can be both greenhouse gas sources and sinks.

Relevant greenhouse gas storages in the forest:

• Above-ground living biomass (trees, shrubs, ground vegetation)

• Below-ground living biomass (roots of trees, shrubs, ground vegetation)

• Deadwood (from trees and shrubs, standing and lying) 10-30% of total biomass

• Litter layer (partially decomposed biomass lying on the ground)

• Soil carbon (mineralised C component in soil)

In principle, all greenhouse gas storages could be taken into account by measuring them or estimating with reliable models. For practical reasons, non-tree biomass, deadwood, litter layer, and soil carbon can be omitted. This is conservative since these storages align with the timber stock or are negligible in quantity (above-ground non-tree biomass, ground vegetation).

Greenhouse gas emissions, e.g., from burning logging residue, soil cultivation, artificial fertilizers, and emissions from the decomposition of N-binding species cannot be identified as being caused by the project. These emissions, which are connected with timber use and stock establishment, tend to decrease due to project activities (reduced timber use). Therefore, it is conservative that such emissions are not considered as baseline or project emissions for the method.

The storage (timber stock) is influenced by the following dynamic parameters:

• Harvest (source)

• Growth (sink)

• Mortality / Risk (source)

6.4.1 Carbon sources, sinks, and storage controlled by the project operator

The main C storage is the living tree biomass, which is directly influenced by the project owner through timber use. The timber stock is determined through usual recognized methods of forest inventory or stock estimation. It is then deduced to the biomass of the entire tree using the relevant conversion factors.

Yield and stock models refer always to the living timber reserve (above-ground). For the conversion from living standing timber reserve to the biomass of the entire tree, there are corresponding conversion factors (Root to shoot ratio, Biomass Expansion Factors BEF, e.g., Ref. 06). The timber stock is recorded by conventional inventories and timber use by conventional measurement methods. Both data sources are converted to the living tree biomass.

Project emissions are greenhouse gas emissions that are generated by the project, such as harvesting or planting, construction and maintenance of roads, transportation, forester's planning and control trips, and biodiversity measures. These emissions are lower or at most equal to those of standard management due to the adapted management.

Therefore, the project emissions are conservatively assumed to be zero in this methodology.

6.4.2 Carbon sources, sinks, and storage related to the climate protection project

Non-tree biomass (shrubs, ground vegetation, litter layer) can be credited if recognized methods are applied for determination. The non-tree biomass can also be omitted. This is conservative, as the amount is negligible compared to tree biomass.

Deadwood can constitute a significant portion of the biomass in near-natural forest stands. The proportion of deadwood increases with the age and the timber stock of forest stands, often due to long-term non-use. The deadwood stock aligns with the standing living timber stock. Decomposition is very slow. Over the project duration, thick trunks do not completely decompose. If recognized methods are applied for measurement or estimation of the deadwood volume, this C storage can be credited in the project. It is conservative not to account for deadwood in the project.

Soil Carbon

In temperate zone forests, soil carbon accounts for half to two-thirds of the total carbon (Ref. 27, 40, 54, 65 cited in Ref. 64). Some underestimation arises from the fact that more C is stored under large trees than between the trees (Ref. 59). Usually, soil C between the trees is measured. Furthermore, carbon continues to accumulate in the soil of natural forests over centuries Ref. 28. A literature review on this topic can be found in Ref. 66 considering Ref. 58, 59, 60, 61, 67.

In the soil of normal sites, approximately the same amount of carbon is present as in the living biomass (Ref. 10, 40). For every ton of CO₂ stored in trees, another ton is expected in the soil. The storage aligns with the living biomass. However, soil carbon is only measurable through laboratory techniques, with an effort hardly conceivable on the operational level. Moreover, soil carbon reacts slowly to management measures (Ref. 27, 35). Soil carbon can be fully credited if recognized methods for assessment and monitoring are used. It is conservative not to account for soil carbon in the project.

6.4.3 Determination of living tree biomass from timber stock (storage)

Recognized methods of timber stock inventory are applied, usually on a sample basis with defined accuracy for tree species and/or groups of tree species. Inventory procedures at different times must be identical or conservative to each other to avoid overestimating the sink performance. For sample inventories, a standard error of at most 5% with a confidence range of 95% is permitted. If the error is higher, the difference to 5% must be considered in the project assumptions. This inventory error can be calculated using permanent sample inventories, two-phase inventories, and inventories with synthetic estimators. Other inventory procedures must state a comparable, verifiable degree of accuracy. If no inventory data is available and estimation procedures are used, assumptions must be made conservatively to rule out overestimation of sink performance. The standing timber stock is measured in cubic meters of stem wood, separated by tree species or groups of tree species. The standing timber stock in m3 is converted into tCO₂e of living tree biomass using recognized conversion procedures.

Further relevant storages can be credited if they are captured with recognized methods and conservatively converted into tCO₂e.

Schematic conversion of stem wood to CO2e according to Ref. 6 (adjusted)

As a rule, national conversion factors are used (see country modules). If such bases are not available, other applicable conversion factors are used, such as Ref. 73.

6.4.4 Determination of use (source)

Use can be determined in one of the following two ways:

1. The timber use is measured standing in m3. The same conversion procedures from m3 to tCO₂e as for stock may be used. Recognized methods are used (grouping at 1.3 meters height, using a recognized volume tariff). Supplementary estimates should be handled conservatively.

2. Timber use is measured after the harvest (harvest volume lying measure, harvester measure, factory measurement, estimates): The volume is completely recorded. Estimates are to be made conservatively. Harvest losses are additionally considered.

As a rule, national conversion factors are used (see country modules). Recognized estimation and calculation methods are applied to deduce from the harvested masses m3 to the standing harvest volume in m3 and from there to tCO₂e. Conversions should be undertaken conservatively. Harvested wood is included as a CO₂ source in the calculation.

6.4.5 Determination of growth (sink)

Growth can be determined in two ways:

1. Growth is derived from follow-up inventories.

2. Growth is estimated.

To 1. growth is derived from follow-up inventories (stock change method): summarizing, two stocks are compared. Usage and mortality are considered in this. The difference directly results in the sink performance.

To 2. growth is derived from models: yield table models or other growth models provide the site class based on the natural site assuming certain management concepts for tree species. Yield table models give growth in volume cubic meters (Vfm) or harvest cubic meters (Efm). Back calculation into tCO₂e is conservatively done with recognized factors.

6.4.6 Quantitative determination of sink performance

Basically, the method is based on the formulas of the AR CDM method AR-AMS0001. IPCC 2006, GL for AFOLU (Ref. 12)

The formulas of the CDM methodology are used as follows:

• Reference scenario (Baseline): Equation 1

• Baseline sink: Equation 10

• For the conversion of timber stock into biomass of the living trees, recognized conversion factors BEF are used. Equations 2-9, 15, and 16 are therefore not applied. The national biomass expansion factors BEF consider the entire tree biomass and not just the above-ground. The variable for the root to shoot ratio is therefore not applied.

• For the ex-ante calculation of the sink performance, equations 11-14. 17 and 18 are used.

• Leakage is assumed to be zero, therefore equation 19 is applied. The conditions for this should be noted in Chap. 6.5.
• The total net sink performance is calculated according to equation 21.

• The VER are time-restricted to the monitoring period, equations 22 and 23 are not applied.

• For ex-post calculation, equations 24, 29, 35, and 36 are applied. The remaining equations are not relevant due to the use of recognized conversion factors.

6.4.6.1 Determination of the reference scenario (Baseline)

Carbon stock in the reference scenario

In equation 1 according to the tool, above-ground and below-ground biomass are added. This is superfluous due to the use of BEF.

Equation 1: $\Delta C_{\mathit{BSL},t} = (B_{(t)} - B_{(t-1)}) \cdot \frac{44}{12}$

corresponds to equation 10 in AR CDM method AR-AMS0001, whereby

$\Delta C_{\mathit{BSL},t}$ = C - stock change in the reference scenario (without project) in year t (tCO₂/a)\n= Net greenhouse gas sink or source in the reference scenario in year t (tCO₂/a)

$B_{(t)}$ = C - stock in the reference scenario (without project) in year t (tC)

$B_{(t-1)}$ = C - stock in the reference scenario (without project) in year t-1 (tC)

$\frac{44}{12}$ = $\frac{CO_{2}}{C}$

Example: Term 30 years,\nStock of the reference scenario at the beginning of the project (Baseline): $B_{(t0)}$ = current stock

Target stock of the reference scenario (Baseline): $B_{(t30)}$ = normal stock derived from ET or other literature

Normal stock: derived in detail or summarised from tree species or group of tree species and site class, or conservatively estimated.

Assumed sink performance of the reference scenario

The target stock and thus the intended sink performance can be chosen within forestry and legal scope. This is a decision of the owner that needs to be coordinated with other operational goals. Starting with the stock at the beginning of the project, this is balanced linearly over the project duration to the target stock at the end of the project.

6.4.6.2 Determination of the project scenario in managed forest (ex-ante)

Equation 2 states that the carbon stocks of the project scenario at the start of the project ($t=0$) must be as high as the carbon stocks of the reference scenario ($t=0$).

Equation 2: $N_{(t=0)} = B_{(t=0)}$

corresponds to Equation 11 in AR CDM Method AR-AMS0001, where

$N_{(t=0)}$ = Carbon stock at time t=0 in the project scenario (tC/ha)

$B_{(t=0)}$ = Carbon stock at time t=0 in the reference scenario (tC/ha)

Equation 3: $N_{(t)} = \sum\limits_{i=1}^{l} (N_{A(t)i} + N_{B(t)i}) \cdot Ai$

corresponds to Equation 12 in AR CDM Method AR-AMS0001, where

$N_{(t)}$ = Carbon stock at time t in the project scenario (tC)

$A_{i}$ = Area of stratum i (ha)

$N_{(A(t)i)}$ = Aboveground carbon stock (tC)

$N_{(B(t)i)}$ = Belowground carbon stock (tC)

Instead of $N_{(A)}$ and $N_{(B)}$, biomass expansion factors (BEF) are used.

Assumed Gross Sink Performance of the Project $\Delta C_{\mathit{PROJ},t}$

Equation 4: $\Delta C_{\mathit{PROJ},t} = (N_{(t)}-N_{(t-1)}) \cdot \frac{44}{12} \Delta {t}$

corresponds to Equation 17 in AR CDM Method AR-AMS0001, where

$\Delta C_{\mathit{PROJ},t}$ = Project Gross Greenhouse Gas Sink (tCO₂/a)

$N_{(t)}$ = Carbon stock at time t in the project scenario (tC)

Estimated Project Emissions $\text{GHG}_{\mathit{PROJ},t}$

Project emissions are assumed to be zero. The conditions for this are mentioned in Chapter 6.3.1 and must be considered.

Equation 5: $\text{GHG}_{\mathit{PROJ},t} = 0$

where

$\text{GHG}_{\mathit{PROJ},t}$ = Project emissions in year t (t CO₂/a)

Estimated External Effects (Leakage)

Leakage is assumed to be zero. The conditions for this are mentioned in Chapter Chapter 6.5 and must be considered.

Equation 6: $L_{t} = 0$

where

$L_{t}$ = Leakage in year t (tCO₂/a)

Actual Sink Performance in the Project Scenario (ex-ante)

The difference between the reference scenario and the project scenario results in the actual sink performance:

Equation 7: $\text{VER}_{t} = \Delta C_{\mathit{PROJ},t} - \Delta C_{\mathit{BSL},t} - \text{GHG}_{\mathit{PROJ},t} - L_{t}$

corresponds to Equation 21 in AR CDM Method AR-AMS0001, where

$\text{VER}_{t}$ = Net accountable sink performance in (tCO₂/a)

$\Delta C_{\mathit{PROJ},t}$ = Gross greenhouse gas sink in the project scenario in year t (tCO₂/a)

$\Delta C_{\mathit{BSL},t}$ = Net greenhouse gas sink or source in the reference scenario in year t (tCO₂/a)

$\text{GHG}_{\mathit{PROJ},t}$ = Project emissions in year t (tCO₂/a)

$L_{t}$ = Leakage in year t (t CO₂/a)

6.3.6.3 Determination of Sink Performance in the Managed Forest (ex-post)

In the managed forest, the sink performance (emission reduction) is determined ex-post. The evidence method focuses on the timber stock, which is converted into living tree biomass. The omission of other carbon stores (soil, etc.) is conservative.

Calculation of Sink Performance ex-post

Equation 8: $VER_{total,t} = V_{t} - B_{t} - L$

The sink performance $ER_{total}$ is divided into the sink performance removal $VER_{removal}$ and reduction $VER_{reduction}$. The following applies: $VER_{total,t} = VER_{removal,t} + VER_{reduction,t}$

The sink performance $VER_{removal}$ can be determined in two ways:

1. Stock Change Method:

Equation 9: $VER_{removal,t} = V_{t} - V_{t0} - L$

1. Gain - Loss Method:

Equation 10: $VER_{removal,t} = \sum\limits_{t=1}^{n}(\frac{n}{t}) z - \sum\limits_{t=1}^{n}(\frac{n}{t}) N- \sum\limits_{t=1}^{n}(\frac{n}{t})M-L$

For Equations 9 and 10, the following baseline applies: $B_{removal,t} = V_{t0}$

The sink performance $VER_{reduction}$ is determined as follows. The following applies: $V_{t} <= V_{t0}$

Equation 11: $VER_{reduction,t} = V_{t} - B_{reduction,t} - L$

Hereby Are:

$VER_{t}$ = Carbon sink performance at time t (tC) of type removal, or reduction

$V_{t}$ = Carbon stock at time t (tC)

$V_{t0}$ = Carbon stock at time 0 (tC)

$B_{removal,t}$ = Carbon stock in baseline scenario removal at time t (tC)

$B_{reduction,t}$ = Carbon stock in baseline scenario reduction at time t (tC)

$z$ = Growth (tC)

$N$ = Utilisation (tC)

$M$ = Mortality (tC)

$L$ = Leakage = 0 (tC)