#
Calculating the net amount of abatement and number of ACCUs

This is the final step in the calculations to determine the number of ACCUs that may be issued for a reporting period. At this stage, the total change in carbon stock for the project area is calculated and then converted to tonnes of carbon dioxide equivalents or CO2-e (see Equations NA1, NA2 and NA3 and the net abatement equation tree in Figure 7). An overview of the calculation is given in Section 47.

#### Figure 7: Equation tree for calculating net carbon abatement for a project (click image to enlarge)

### See Figure 7: Equation tree for calculating net carbon abatement for a project

The equation tree in Figure 7 shows how to calculate net abatement. Equations for calculating baseline (highlighted in green) and total project emissions (highlighted in blue) are shown along the bottom of this equation tree for each type of project emission (livestock, synthetic fertiliser, lime, crop residues and irrigation energy use). Total emissions are then subtracted from the baseline amount to give you the net greenhouse gas abatement for your project in t CO2-e.

The equation numbers are at the top left of each box. Note that two calculations from before the current reporting period do not have equation numbers (project net abatement, and total change in emissions from all sources). However, in the first project reporting period, both values are zero.

The steps are:

- Calculate the amount of carbon sequestered in the soil over your project area for the duration of your project as t CO2-e according to Equations SC1 (A or B) and SC2 in Section 49.
- Calculate baseline emissions from each source relevant to your project area as t CO2-e/y, as outlined in Figures 2-5.
- Calculate project emissions from each source relevant to your project area as t CO2-e or t CO2-e/y, as outlined in Figure 6.
- Calculate the total change in emissions as t CO2-e for your project. Some emission types have alternative equations for calculating the material difference in emissions, depending on which baseline was applied (such as livestock baselines A and B; see Sections 72–75). You must also estimate the material change in emissions from all sources for each CEA for the reporting period, as shown in Equation EALL1 (Section 81) and Equation NA1 (Section 82).
- Use Equation NA3 to calculate the total net abatement from total change in emissions (from Equation NA1) and total sequestration (from Equation NA2).
- If you have reported a depletion event in a CEA, use Equations D1–D4 (not shown in Figure 7: see following box) to calculate the number of years until you can start to claim any carbon sequestration.

### Depletion events

If project management activities stop in a CEA and are not replaced by other approved activities, or if there is 30% bare soil in a CEA, the soil organic carbon that has already been sequestered starts to be released back into the atmosphere. This is called ‘carbon depletion’.

For example, a depletion event occurs if a pasture renovation, soil acidity or nutrient management strategy is not followed. Sections 89–91 describe how to determine if a depletion event has occurred; when the event is taken to have stopped; and how to account for the event. Section 97 outlines when you must notify the Regulator of the depletion event.

If a depletion event occurs, the amount of carbon sequestered in the entire CEA is taken to be zero, until the soil carbon is replenished after project management activities recommence (Sections 90–91).

Once a depletion event is taken to have commenced, the depletion rate of soil carbon is calculated at a constant annual rate of one-seventh of the carbon sequestered, until seven years have elapsed. The replenishment rate is defined by the project management activity being undertaken and its sequestration value. You need to use Equations D1–D4 to calculate how long the replenishment period will last once you have recommenced project management activities. This will determine when you can start to claim carbon sequestration in that CEA.