Choice of method

A decision tree is provided in Figure 11.4 to assist inventory compilers with selection of the appropriate tier. Tier 1

CO2 Emissions from additions of carbonate limes to soils can be estimated with Equation 11.12:

Equation 11.12 Annual CO2 emissions from lime application

C02-C Emission = (MLlmestone • EFLimestone ) + (MDolomlte • EFDolomlte)

Where:

CO2-C Emission = annual C emissions from lime application, tonnes C yr-1 M = annual amount of calcic limestone (CaCO3) or dolomite (CaMg(CO3)2), tonnes yr-1 EF = emission factor, tonne of C (tonne of limestone or dolomite) -1

Procedural steps for calculations

The steps for estimating CO2-C emissions from liming are:

step 1: Estimate the total amount (M) of carbonate containing lime applied annually to soils in the country, differentiating between limestone and dolomite (Note: M should include all lime applied to soils even the proportion applied in mixture with fertilizers). Note that while carbonate limes are the dominant liming material used in managed systems, oxides (e.g., CaO) and hydroxides of lime are used to a limited extent for soil liming. These materials do not contain inorganic carbon and are not included in calculations for estimating CO2 emissions from application to soils (CO2 is produced in their manufacture but not following soil application).

Step 2: Apply an overall emission factor (EF) of 0.12 for limestone and 0.13 for dolomite. These are equivalent to carbonate carbon contents of the materials (12% for CaCO3, 13% for CaMg(CO3)2 )). The uncertainty is -50% based on approximations suggesting emissions may be less than half of the maximum value, which is the current factor value (West and McBride, 2005) (Note: uncertainties can not exceed the emission factors because these value represent the absolute maximum emissions associated with liming).

Step 3: Multiply the total amounts of limestone and dolomite by their respective emission factors, and sum the two values to obtain the total CO2-C emission.

Multiply by 44/12 to convert CO2-C emissions into CO2.

Tier 2

Tier 2 inventories also use Equation 11.12 and procedural steps, which were provided in the Tier 1 approach, but incorporate country-specific data to derive emission factors (EF).

Overall, the CO2 emissions from liming are expected to be less than using the Tier 1 approach, which assumes that all C in applied lime is emitted as CO2 in the year of application. However, emissions are likely to be less than assumed using the Tier 1 approach because the amount of CO2 emitted after liming will depend on site-specific influences and transport of dissolved inorganic C through rivers and lakes to the ocean. Tier 2 emission factors could be used to better approximate the emissions.

Tier 3

Tier 3 methods use more sophisticated models or measurement procedures, and the procedural steps will depend on the country-specific estimation system. Such an analysis would likely necessitate modelling carbon fluxes associated with primary and secondary carbonate mineral formation and dissolution in soils, as well as the leaching and transport of dissolved inorganic C. Note that increases in soil inorganic C or dissolved inorganic C attributed to liming does not constitute a net removal of CO2 from the atmosphere. Rather, carbonate-C from liming that is not returned to the atmosphere is considered a net reduction in the emissions associated with this practice. See the Tier 3 section for soil inorganic C in Chapter 2 for additional discussion (Section 2.3.3.1 on Change in Soil C Stocks).

Figure 11.4 Decision tree for identification of appropriate tier to estimate CO2 emissions from liming.

Figure 11.4 Decision tree for identification of appropriate tier to estimate CO2 emissions from liming.

Policy Factors

Note:

1: See Volume 1 Chapter 4, "Methodological Choice and Identification of Key Categories" (noting Section 4.1.2 on limited resources), for discussion of key categories and use of decision trees.

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