Choice of method

As is the case for emissions from cement production, there are three basic methodologies for estimating emissions from lime production: an output-based approach that uses default values (Tier 1), an output-based approach that estimates emissions from CaO and CaO-MgO production and country-specific information for correction factors (Tier 2) and an input-based carbonate approach (Tier 3). Unlike the Tier 3 method which requires a plant-specific assessment, the Tier 1 and Tier 2 methods can be applied either to national, or where possible, plant statistics. The choice of good practice method depends on national circumstances, as shown in Figure 2.2.

It is good practice to assess the available national statistics for completeness, and for the ratio of limestone to dolomite used in lime production. Some industries produce non-marketed lime reagents for their own processes (e.g., the iron and steel industry for use as a slagging agent). All lime production, whether produced as a marketed or a non-marketed product should be reported under IPCC Subcategory 2A2 Lime Production.

Figure 2.2 Decision tree for estimation of CO2 emissions from lime production

Figure 2.2 Decision tree for estimation of CO2 emissions from lime production

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.

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.

TIER 1 METHOD

The Tier 1 method is based on applying a default emission factor to national level lime production data. While country-specific information on lime production by type (e.g., high calcium lime, dolomitic lime, or hydraulic lime) is not necessary for good practice in Tier 1, where data are available to identify the specific types of lime produced in the country, this may be used. It is not necessary for good practice to account for LKD in Tier 1.

TIER 2 METHOD

Where national level data are available on the types of lime produced, it is good practice to estimate emissions using Equation 2.6. The Tier 2 method requires country-specific information on the proportion of hydrated lime produced. Typical plant-level ratios of lime product to LKD production should be obtained.

Equation 2.6

Tier 2: Emissions based on national lime production data by type

CO2 Emissions = £ {EFllme l • Mt• CFlkd l • Ch l)

Where:

CO2 Emissions = emissions of CO2 from lime production, tonnes

EF limei = emission factor for lime of type i, tonnes CO2/tonne lime (see Equation 2.9)

Ml,1 = lime production of type i, tonnes

CF lkdi = correction factor for LKD for lime of type i, dimensionless

This correction can be accounted for in a similar way as for CKD (Equation 2.5, but omitting the factor (Efc/EFcl))

Ch,i = correction factor for hydrated lime of the type i of lime, dimensionless (See discussion under Section 2.3.1.3, Choice of Activity Data.)

i = each of the specific lime types listed in Table 2.4 TIER 3 METHOD

Tier 3 is based on the collection of plant-specific data on the type(s) and quantity(ies) of carbonate(s) consumed to produce lime, as well as the respective emission factor(s) of the carbonate(s) consumed. The Tier 3 method to estimate emissions from lime production is similar to Equation 2.3 for cement production, except there is a correction for LKD, as opposed to CKD and there is no need to correct for emissions from carbon-bearing non-fuel materials. Unlike the case with CKD and cement kilns, LKD is seldom recycled to the lime kiln (but LKD can be used as a feed to a cement kiln). For purposes of estimating emissions in Equation 2.7 it is assumed that no LKD is recycled to the kiln.

Where:

CO2 Emissions = emissions of CO2 from lime production, tonnes

EFi = emission factor for carbonate i, tonnes CO2/tonne carbonate (see Table 2.1)

Mi = weight or mass of carbonate i consumed, tonnes

Fi = fraction calcination achieved for carbonate i, fraction3

Md = weight or mass of LKD, tonnes

Cd = weight fraction of original carbonate in the LKD, fraction2. This factor can be accounted for in a similar way as CKD.

Fd = fraction calcination achieved for LKD, fractiona

EFd = emission factor for the uncalcined carbonate in LKD, tonnes CO2/tonne carbonateb Notes on defaults for Equation 2.7

a: Calcination fractions: In the absence of actual data, it is consistent with good practice to assume that the degree of calcination achieved is 100 percent (i.e., Fi = 1.00) or very close to it. For LKD, a Fd of <1.00 is more likely but the data may show high variability and relatively low reliability. In the absence of reliable data for LKD, an assumption of Fd = 1.00 will zero out the subtraction correction for uncalcined carbonate remaining in LKD.

b: Because calcium carbonate is overwhelmingly the dominant carbonate in the raw materials, in the absence of better data it may be assumed that it makes up 100 percent of the carbonate remaining in the LKD. It is thus consistent with good practice to set Cd equal to the calcium carbonate ratio in the raw material feed to the kiln. Likewise, in the absence of better data it is consistent with good practice to use the emission factor for calcium carbonate for EFd.

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