TYPE: Sequestration methodology

NOTE: This method was revoked in 2018, with  any new direct measurement soil carbon projects from that time subsequently registered under the Carbon Credits (Measurement of Soil Carbon Sequestration in Agricultural Systems) Methodology Determination 2018.

Summary

This methodology is concerned with sequestering carbon in soils within grazing systems. Within these systems, land can be managed using a range of activities (for example, converting cropland to permanent pasture, rejuvenating pastures or altering grazing patterns) to build soil carbon.

In additional to measuring carbon sequestered in soils, changes in emissions from other sources (including from livestock, tillage, synthetic fertiliser application) must be measured and included in calculations to determine net abatement (which then determines the number of ACCUs that may be issued for the project).

This soil carbon methodology is based on direct measurement and requires that a detailed sampling and testing regime (including statistical analysis) be undertaken over the course of the project. The sampling and testing must be undertaken by a qualified technician.

Methodology details

Management actions

Soil Carbon in Grazing Systems projects can use a range of actions to build soil carbon, as long as at least one of the project management actions is new. New management actions are those that are different to the way an area had been managed previously (historic management actions) and may include, but are not limited to:

• converting from continuous cropping to permanent pasture;

• undertaking pasture cropping;

• managing pasture by implementing or changing pasture irrigation, applying organic or synthetic fertiliser to pastures, or rejuvenating pastures, including by seeding; or

• managing grazing by changing stocking rates or altering the timing, duration, and intensity of grazing.

Choosing a suitable management action or actions to build soil carbon is a decision the person responsible for running a project must make.

There is no guarantee that any one of the management actions listed here will build soil carbon on any particular property and it is recommended that proposed project management actions are researched and expert advice sought on what will best suit a particular project area. 

The Clean Energy Regulator will need evidence showing that at least one of the project management actions is new and that the project management actions as a whole will have a reasonable chance of increasing carbon inputs into the soil, reducing soil carbon losses, or both. Some management actions are not eligible including:

• permanent de-stocking;

• applying biochar or amendments containing coal to the soil;

• bare fallow;

• applying organic fertiliser that contains crop residue, hay or straw unless they were part of a waste-stream from intensive animal production, food processing or manufacturing processes; or

• clearing woody vegetation unless done to manage re-growth of invasive woody weeds.

Project location requirements

Section 2.4 of the methodology determination sets out the requirements for the land on which the project mechanism is implemented: 

- the land must be within Australia, excluding external territories;

- the land must be made up of areas that were under either:

  (a) permanent pasture for the 5 year period immediately before:

   (i) an application for declaration of the project as an eligible offsets project is made; or
   (ii) the first day of the baseline sampling round; whichever is the earlier; or

  (b) continuous cropping for the five year period immediately before:

   (i) an application for declaration of the project as an eligible offsets project is made; or
   (ii) the first day of the baseline sampling round; whichever is the earlier.

- evidence must be provided to demonstrate, to the satisfaction of the Regulator, that the land was managed as set out above:

  (a) as permanent pasture; or

  (b) as a continuous cropping system.

- if any part of the land was subject to continuous cropping then the new management actions must include converting that part of the land to permanent pasture.

Establishing a project area

The area in which the project will occur is to be identified using the CFI Mapping Guidelines and then divided into one or more carbon estimation areas (CEAs), and if applicable, exclusion areas.

CEAs are the areas of the project where changes in soil carbon stock will be measured (using detailed sampling as set out below). Exclusion areas are those parts of the project area where the project will not take actions to build soil carbon and may include a road, a building or another area not used for primary production. The project can include one CEA or the project area can be divided into multiple CEAs.

If one part of the project area is very different to another, it may be better to establish more than one CEA because it is easier to detect changes in soil carbon stock over time in more homogeneous CEAs. The boundaries of a CEA must be defined in accordance with the CFI Mapping Guidelines and the CFI soil sampling design method (which is included in the CFI Soil Sampling Design Method and Guidelines). Once the boundaries of a CEA have been established they cannot change.

Preparing a sampling plan

A sampling plan must be prepared in accordance with the instructions in the CFI soil sampling design method. The sampling design method can be implemented on all eligible project areas, and knowledge of the spatial variability of soil carbon on a property is not needed to use this method. The soil sampling design requires CEAs be divided into equal area strata with randomly allocated sampling locations in each.

For example, a square CEA may be divided up into a nine square strata using a three by three (3 x 3) regular grid, with four sampling locations randomly allocated in each stratum. Not all project areas will have evenly shaped CEAs and the CFI Soil Sampling Design Method and Guidelines set out further information on how to divide up CEAs into strata. A soil sample from one sampling location in each stratum in the CEA is combined to form a composite (see Conduct baseline soil sampling).

A minimum of three strata and three composites (three sampling locations in each stratum) must be included in each CEA, however taking more samples, particularly by increasing the number of strata, will greatly improve the ability to detect changes in soil carbon stock over time. Care should be taken when preparing a sampling plan to ensure it is optimal for detecting changes in soil carbon stock over time while considering the financial resources available for soil sampling.

The CFI Soil Sampling Design Method and Guidelines set out some of the key factors that should be considered when developing a sampling plan.

Conducting baseline soil sampling

For a Soil Carbon in Grazing Systems project, a baseline sampling round provides an initial estimate of the soil carbon stock in each CEA. A baseline sampling round must be done after the project start date and before project management actions start on a CEA.

It is recommended that the time between the project start date and the baseline sampling round is minimised to allow plenty of time for follow-up sampling rounds in the first reporting period. A baseline sampling round must be conducted at an appropriate time of year, which is generally when soil moisture conditions are right for collecting soil samples (see Division 4.2 of the methodology determination and explanatory statement). Choosing the time of year is important and must be done carefully because subsequent sampling rounds must be conducted at approximately the same time of year.

There is a 60-day window to conduct each CEA baseline sampling round, and a six-month window to conduct all CEA baseline sampling rounds in a project area. Soil samples must be collected to a minimum depth of 30 cm, but may be collected deeper. All reasonable efforts must be made to sample to the same nominated sampling depth at all sampling locations in the CEA. If the nominated sampling depth is greater than 30cm, the upper layer (0-30cm) and deeper layer (30+cm) must be prepared and analysed separately (see Division 4.2 of the methodology determination and explanatory statement). Collecting and preparing samples in the field must be conducted by a qualified technician (see Division 4.2 of the methodology determination).

The technician needs to locate the sampling locations identified in a sampling plan in accordance with the CFI soil sampling design method. The technician must also conduct sample collection and preparation in accordance with the CFI soil sampling and analysis method, which is included in the CFI Soil Sampling and Analysis Method and Guidelines. A soil sample from one sampling location in each stratum of a CEA must be combined to form a composite. A sub- sample is taken from each composite and sent to an accredited laboratory for organic carbon and water content analysis in accordance with the CFI soil sampling and analysis method.

Exclusive management actions

From the activity start date until the end of the final crediting period, the only actions that may be conducted on the project area are those identified as project management actions. The Clean Energy Regulator must be notified of any changes to the project management actions before the end of the final crediting period.

Project management actions can be described broadly to avoid needing to update the Clean Energy Regulator of minor changes, and should include all management actions likely to be conducted between the activity start date and the end of the final crediting period. For example, a project management action may be described as high intensity, short-rotation grazing without specifying the precise stocking density and duration of rotations.

Follow up soil sampling

Once project management actions have started, follow-up soil sampling rounds must be undertaken to estimate changes in soil carbon stocks over time. For these followup sampling rounds, the same CEAs and strata must be sampled and the CEA and strata boundaries must not change.

New sampling locations can be randomly allocated within each strata, or offset by a small distance from the original sampling locations, in accordance with the CFI soil sampling design method. Follow-up sampling rounds must be conducted at the same time of year (plus or minus 30 days) as the baseline sampling round for each CEA.

This reduces the influence of seasonal variability in soil carbon stocks on measured soil carbon change over time. The time between consecutive sampling rounds (sampling interval) must be no less than one year and no more than five years. A fixed sampling interval is not prescribed, but the sampling interval must not vary by more than two years for the project duration.

This ensures that sampling rounds are relatively evenly spaced over the crediting period, while providing flexibility to change the frequency of sampling rounds according to the circumstances of your project. It is recommended that at least five sampling rounds are undertaken over a 15-year crediting period.

Calculating change in soil carbon

After two sampling rounds, soil carbon stock change is calculated as the difference between the mean soil carbon stocks from the baseline sampling round to the first project sampling round in each CEA. A temporary 50 per cent discount is applied to the total change in soil carbon in the project area (the sum of the soil carbon change in all CEAs) (see Subdivision 6.1.3 of the methodology determination and explanatory statement).

This reduces the risk of overcrediting early in the project, by limiting the chance that ACCUs are issued for change that is mostly related to seasonal conditions rather than management. It also reduces the risk that projects have to maintain unrealistically high soil carbon stocks. The 50 per cent discount is only temporary; after three or more sampling rounds there is no discount applied and the discounted soil carbon change can be regained if soil carbon stock has been maintained.

After three or more sampling rounds, changes in soil carbon stock are calculated based on fitting a trend line (the slope of a linear regression) through the measured soil carbon stock at each sampling round (see Subdivision 6.1.5 of the methodology determination and explanatory statement).

A trend line more accurately estimates the average change in soil carbon over time due to the project management actions, as it smooths the fluctuations in soil carbon stocks that can occur because of natural variation such as wet and dry periods.

The change in soil carbon in a reporting period that includes three or more sampling rounds is determined by multiplying the slope defined for the trend line by the duration of the project and then subtracting any calculating the change in soil carbon between the baseline sampling round and the most recent sampling round, and subtracting any soil carbon increases already reported rewarded (See Subdivision 6.1.6 of the methodology determination). This is to ensure ACCUs are issued for individual reporting periods only and not cumulatively.

The CFI Soil Carbon in Grazing Systems Calculator can help calculate soil carbon stock change in accordance with the requirements of the methodology determination. It includes a simple data entry interface for you to enter the results of your soil sampling and analysis, and calculates the values for soil carbon stock change needed for your offsets report.

The methodology also includes statistical adjustment to the sampled soil carbon to ensure that the mean change in soil organic carbon stock would be exceeded 60 per cent of the time.

Calculating emissions from the project

Every project needs to take into account emissions that arise from running it. These emissions must be included in the calculations that determine the net amount of carbon a project has stored in a reporting period and crediting period. To calculate changes in emissions, it is necessary to establish ‘baseline emissions' for each relevant source - that is, the emissions that are assumed to have occurred in the absence of the project.

Project management actions to build soil carbon on grazing land could affect emissions from sources including livestock, tillage, synthetic fertiliser and lime application. The methodology determination provides some allowance for emissions to increase or decrease before they must be accounted for. Only material changes, which are changes of a certain magnitude relative to the baseline, must be included in the net abatement calculation.

The methodology determination establishes a series of standardised approaches to estimating baseline emissions. This provides the flexibility for many different types of projects to participate, including projects with limited historical data. However, these approaches only estimate baseline emissions and may not precisely reflect the situation for each specific project.

Baseline emissions from each source need to be calculated according to the appropriate method set out in the methodology determination. In some cases this will involve using historic data, but if this data is unavailable, baseline emissions can be calculated using one of the alternative approaches.

For example, as a default, baseline emissions from livestock must be calculated using historic property livestock numbers. Emissions from an individual source may increase or decrease as a result of a project. For example, an increase in stocking rates during the project will increase emissions from livestock.

Calculating net abatement

The net abatement number for each reporting period is the change in soil carbon stocks for the reporting period less any increase in emissions from all sources (livestock, synthetic fertiliser, lime and tillage). If the net abatement number is positive, the project may be eligible to receive ACCUs. If the net abatement number is negative, for example because there was a small increase in soil carbon stocks and a large increase in other emissions, the project would not be eligible to receive ACCUs.

This negative net abatement number would be carried over into later reporting periods to ensure that all increases in emissions are accounted for over the crediting period.

Record keeping requirements

The methodology includes very detailed record keeping requirements. Essentially, auditable standard records must be kept for each soil sampling round, for emissions from other sources within the project areas, and for all project management actions.