## Choice of method methodology FOR CO2

The IPCC Guidelines outline several approaches for calculating CO2 emissions from ferroalloy production. For practical purposes, this section adopts a mass balance approach where all CO emitted is reported as emitted CO2. The choice of a good practice method depends on national circumstances as shown in the decision tree in Figure 4.9. The Tier 1 method calculates emissions from general emission factors applied to a country's total ferroalloy production. The Tier 1 method is very simple, and it may lead to errors due to its reliance on assumptions rather than actual data. Therefore it is appropriate only when ferroalloy production is not a key category. The Tier 2 method calculates emissions from a known consumption of reducing agents, preferably from plant-specific consumption data, but alternatively from industry-wide data using emission factors similar to those used to estimate combustion emissions. The Tier 3 method is based on facility-specific emissions data.

Tier 1 method: production-based emission factors

The simplest estimation method is to multiply default emission factors by ferroalloy product type as shown in Equation 4.15.

Where:

ECo2 = CO2 emissions, tonnes

MPj = production of ferroalloy type i, tonnes

EFi = generic emission factor for ferroalloy type i, tonnes CO2/tonne specific ferroalloy product

Tier 2 method: production-based, raw material specific emission factors

An alternate approach is to use emission factors for the reducing agents. For the other raw materials and products carbon contents should be considered.

Box 4.1

Definitions for words/symbols used in equations in this section Content means weight-fraction in all equations Z means the sum of all i, h, j, k or l

Equation 4.16

CO2 EMISSIONS FOR FERROALLOY PRODUCTION BY TIER 2 METHOD

h 12 44 12

EC02 = Z (reducing agent,i • EFreducing agent,i )+ Z (ore,h • CContentore,h )• ih

+ Z slag forming material, j • CContentslag forming material, j) • . ~

product,k) 12

Z non - product outgoing stream, l * CContentnon - product outgoing stream,l) * . l 12

Where:

ECO2 = CO2 emissions frm ferroalloy production, tonnes Mreducing agent, i = mass of reducing agent i, tonnes

EFreducing agent, i = emission factor of reducing agent i, tonnes CO2/tonne reducing agent More, h = mass of ore h, tonnes

CContentore, h = carbon content in ore h, tonnes C/tonne ore Mslag forming material, j = mass of slag forming material j, tonnes

CContentslag forming materiai, j = carbon content in slag forming material j, tonnes C/tonne material Mproduct, k = mass of product k, tonnes

CContentproduct, k = carbon content in product k, tonnes C/tonne product Mnon-product outgoing stream, l = mass of non-product outgoing stream l, tonnes

CContentnon-product outgomg stream, l = carbon content in non-product outgoing stream l, tonnes C/tonne

The constant 44/12 is the multiplication factor for the mass of CO2 emitted from each mass unit of total carbon used.

Tier 3 method: calculations based on amounts and analyses of reducing agents

The producers use coal and coke with different contents of ash, fixed carbon and volatiles. Further, the amounts of carbon in carbonate ores and slag forming materials will vary. The most accurate method is therefore to calculate the CO2 emissions from the total amount of carbon in reducing agents, electrode paste, ores, slag forming materials and products, and this calculation is carried out for each ferroalloy produced.

Equation 4.17

CO2 EMISSIONS FOR FERROALLOY PRODUCTIION BY TIER 3 METHOD

reducing agent,i j ^

+ S slag forming material, j • CContentslag forming material, j j• 1,, j product,k • CContent

S non-product outgoing stream,l • CContent non - product outgoing stream,l) • i l 12

Where:

ECO2 = CO2 emissions frm ferroalloy production, tonnes Mreducing agent, i = mass of reducing agent i, tonnes

CContentreducing agent, ¡ = carbon content in reducing agent i, tonnes C/tonne reducing agent More, h = mass of ore h, tonnes

CContentore, h = carbon content in ore h, tonnes C/tonne ore Mslag forming material, j = mass of slag forming material j, tonnes

CContentslag forming materiai, j = carbon content in slag forming material j, tonnes C/tonne material -M-product, k = mass of product k, tonnes

CContentproduct, k = carbon content in product k, tonnes C/tonne product Mnon-product outgoing stream, l = mass of non-product outgoing stream l, tonnes

CContentnon_product outgoing stream, l = carbon content in non-product outgoing stream l, tonnes C/tonne

The constant 44/12 is the multiplication factor for the mass of CO2 emitted from each mass unit of total carbon used. The calculation will have good accuracy if analyses of total carbon in all reducing agents are available.

Figure 4.9 Decision tree for estimation of CO2 emissions from ferroalloy production

Figure 4.9 Decision tree for estimation of CO2 emissions from ferroalloy 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.

### METHODOLOGY FOR CH4 AND DISCUSSION OF N2O EMISSIONS

The heating of carbon materials in the furnace releases volatiles including methane. With open or semi-covered furnaces - predominantly used for FeSi and Si ferroalloy production - most of the volatiles will burn to CO2 above the charge, in the hood and off-gas channels, but some will remain un-reacted as CH4 and NMVOC. The amounts depend on the operation of the furnace. Sprinkle-charging will reduce the amounts of CH4 compared to batch-wise charging. Increased temperature in the hood (less false air) will reduce the content of CH4 further.

The IPCC Guidelines outline several approaches for calculating CH4 emissions from FeSi- and Si- ferroalloy production. The choice of a good practice method depends on national circumstances as shown in the decision tree in Figure 4.10. The Tier 1 method calculates emissions from general emission factors applied to a country's total ferroalloy production. The Tier 1 method is very simple, and it may lead to errors due to its reliance on assumptions rather than actual data. Therefore it should only be used when ferroalloy production is not a key category. The Tier 2 method calculates emissions from operation-specific emission factors. The Tier 3 method uses facility-specific emissions data.

The errors associated with estimates or measurements of N2O emissions from the ferroalloys industry are very large and thus, a methodology is not provided.

Figure 4.10 Decision tree for estimation of CH4 emissions from FeSi and Si alloy production

Figure 4.10 Decision tree for estimation of CH4 emissions from FeSi and Si alloy 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: FeSi and Si alloy production-based emission factors

The simplest estimation method is to multiply default emission factors by Si-alloy product type. Total emissions are calculated according to:

Equation 4.18

CH4 emissions for ferroalloy production by the Tier 1 method

Where:

ECH4 = CH4 emissions, kg

MPi = production of Si-alloy i, tonnes

EFi = generic emission factor for Si-alloy i, kg CH4/ tonne specific Si-alloy product

Tier 2 method: FeSi and Si alloy production-based, operation specific emission factors

The Tier 2 method is also based on emission factors but unlike the Tier 1 method, these are operation specific. Tier 3 method: Direct measurements

Inventory compilers are strongly encouraged to measure CH4 emissions where emissions from ferroalloys industry is a key category.