Chapter 4: Metal Industry Emissions

CHAPTER 4

METAL INDUSTRY EMISSIONS

2006 IPCC Guidelines for National Greenhouse Gas Inventories

4.1

Volume 3: Industrial Processes and Product Use

Authors
Section 4.1
Jerry Marks (USA)Section 4.2
Jonathan Lubetsky (USA) and Bruce A. Steiner (USA)Section 4.3
Tor Faerden (Norway), Jonathan S. Lubetsky (USA), Tor Lindstad (Norway), Sverre E. Olsen (Norway), andGabriella Tranell (Norway)
Section 4.4
Jerry Marks (USA), William Kojo Agyemang-Bonsu (Ghana), Mauricio Firmento Born (Brazil), Laurel Green(Australia), Halvor Kvande(Norway), Kenneth Martchek (USA), and Sally Rand (USA)Section 4.5
Gabriella Tranell (Norway) and Tom Tripp (USA)Section 4.6
Jonathan S. Lubetsky (USA) and Jerry Marks (USA)Section 4.7
Jonathan S. Lubetsky (USA)Contributing Authors
Section 4.2
Robert Lanza (USA)Section 4.4
Vince Van Son (USA), Pablo Alonso (France), Ron Knapp (Australia), Stéphane Gauthier (Canada), Michel
Lalonde (Canada), Hézio Ávila de Oliveira (Brazil), and Chris Bayliss (UK)

4.2

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Metal Industry Emissions

Contents
4

Metal Industry Emissions..............................................................................................................................4.8
4.1

Introduction ...........................................................................................................................................4.8

4.2

Iron & steel and Metallurgical Coke Production...................................................................................4.9

4.2.1

Introduction .................................................................................................................................4.11

4.2.2

Methodological issues .................................................................................................................4.17

4.2.2.1

Choice of method: metallurgical coke production .................................................................4.17

4.2.2.2

Choice of method: iron and steel production .........................................................................4.19

4.2.2.3

Choice of emission factors.....................................................................................................4.24

4.2.2.4

Choice of activity data ...........................................................................................................4.28

4.2.2.5

Completeness.........................................................................................................................4.28

4.2.2.6

Developing a consistent time series .......................................................................................4.29

4.2.3

Uncertainty assessment ...............................................................................................................4.30

4.2.4

Quality Assurance/Quality Control (QA/QC), Reporting and Documentation ...........................4.30

4.3

4.2.4.1

Quality Assurance/Quality Control (QA/QC)........................................................................4.30

4.2.4.2

Reporting and Documentation ...............................................................................................4.31

Ferroalloy production..........................................................................................................................4.32

4.3.1

Introduction .................................................................................................................................4.32

4.3.2

Methodological issues .................................................................................................................4.32

4.3.2.1

Choice of method...................................................................................................................4.32

4.3.2.2

Choice of emission factors.....................................................................................................4.37

4.3.2.3

Choice of activity data ...........................................................................................................4.39

4.3.2.4

Completeness.........................................................................................................................4.40

4.3.2.5

Developing a consistent time series .......................................................................................4.40

4.3.3
4.3.3.1

Emission factor uncertainties.................................................................................................4.40

4.3.3.2

Activity data uncertainties .....................................................................................................4.40

4.3.4

4.4

Uncertainty assessment ...............................................................................................................4.40

Quality Assurance/Quality Control (QA/QC), Reporting and Documentation ...........................4.41

4.3.4.1

Quality Assurance/Quality Control (QA/QC)........................................................................4.41

4.3.4.2

Reporting and Documentation ...............................................................................................4.41

Primary aluminium production ...........................................................................................................4.43

4.4.1

Introduction .................................................................................................................................4.43

4.4.2

Methodological issues .................................................................................................................4.43

4.4.2.1

Choice of method for CO2 emissions from primary aluminium production ..........................4.43

4.4.2.2

Choice of emission factors for CO2 emissions from primary aluminium production ............4.47

4.4.2.3

Choice of method for PFCs ...................................................................................................4.49

4.4.2.4

Choice of emission factors for PFCs .....................................................................................4.53

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Volume 3: Industrial Processes and Product Use

4.4.2.5

Choice of activity data ...........................................................................................................4.55

4.4.2.6

Completeness.........................................................................................................................4.55

4.4.2.7

Developing a consistent time series .......................................................................................4.55

4.4.3
4.4.3.1

Emission factor uncertainties.................................................................................................4.56

4.4.3.2

Activity data uncertainties .....................................................................................................4.57

4.4.4

4.5

Quality Assurance/Quality Control (QA/QC), Reporting and Documentation ...........................4.57

4.4.4.1

Quality Assurance/Quality Control (QA/QC)........................................................................4.57

4.4.4.2

Reporting and Documentation ...............................................................................................4.57

Magnesium production........................................................................................................................4.59

4.5.1

Introduction .................................................................................................................................4.59

4.5.2

Methodological issues .................................................................................................................4.61

4.5.2.1

Choice of method...................................................................................................................4.61

4.5.2.2

Choice of emission factors.....................................................................................................4.65

4.5.2.3

Choice of activity data ...........................................................................................................4.66

4.5.2.4

Completeness.........................................................................................................................4.67

4.5.2.5

Developing a consistent time series .......................................................................................4.67

4.5.3

Uncertainty assessment ...............................................................................................................4.68

4.5.4

Quality Assurance/Quality Control (QA/QC), Reporting and Documentation ...........................4.69

4.6

4.5.4.1

Quality Assurance/Quality Control (QA/QC)........................................................................4.69

4.5.4.2

Reporting and Documentation ...............................................................................................4.70

Lead production...................................................................................................................................4.71

4.6.1

Introduction .................................................................................................................................4.71

4.6.2

Methodological Issues.................................................................................................................4.71

4.6.2.1

Choice of method...................................................................................................................4.71

4.6.2.2

Choice of emission factors.....................................................................................................4.73

4.6.2.3

Choice of activity data ...........................................................................................................4.74

4.6.2.4

Completeness.........................................................................................................................4.75

4.6.2.5

Developing a consistent time series .......................................................................................4.75

4.6.3

4.7

Uncertainty assessment ...............................................................................................................4.75

4.6.3.1

Emission factor uncertainties.................................................................................................4.75

4.6.3.2

Activity data uncertainties .....................................................................................................4.75

4.6.4

4.4

Uncertainty assessment ...............................................................................................................4.56

Quality Assurance/Quality Control (QA/QC), Reporting and Documentation ...........................4.76

4.6.4.1

Quality Assurance/Quality Control (QA/QC)........................................................................4.76

4.6.4.2

Reporting and Documentation ...............................................................................................4.77

Zinc production ...................................................................................................................................4.78

4.7.1

Introduction .................................................................................................................................4.78

4.7.2

Methodological issues .................................................................................................................4.78

4.7.2.1

Choice of method...................................................................................................................4.78

4.7.2.2

Choice of emission factors.....................................................................................................4.80

4.7.2.3

Choice of activity data ...........................................................................................................4.80

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Metal Industry Emissions

4.7.2.4

Completeness.........................................................................................................................4.81

4.7.2.5

Developing a consistent time series .......................................................................................4.82

4.7.3

Uncertainty assessment ...............................................................................................................4.82

4.7.3.1

Emission factor uncertainties.................................................................................................4.82

4.7.3.2

Activity data uncertainties .....................................................................................................4.82

4.7.4

Quality Assurance/Quality Control (QA/QC), Reporting and Documentation ...........................4.82

4.7.4.1

Quality Assurance/Quality Control (QA/QC)........................................................................4.82

4.7.4.2

Reporting and Documentation ...............................................................................................4.83

Reference.....................................................................................................................................................4.84

Equations
Equation 4.1

Emissions from coke production (Tier 1) ............................................................................4.17

Equation 4.2

CO2 emissions from onsite coke production (Tier 2) ..........................................................4.17

Equation 4.3

CO2 emissions from offsite coke production (Tier 2)..........................................................4.18

Equation 4.4

CO2 emissions from iron and steel production (Tier 1).......................................................4.21

Equation 4.5

CO2 emissions from production of pig iron not processed into steel (Tier 1) .....................4.21

Equation 4.6

CO2 emissions from production of direct reduced iron (Tier 1) ..........................................4.21

Equation 4.7

CO2 emissions from sinter production (Tier 1) ...................................................................4.21

Equation 4.8

CO2 emissions from pellet production (Tier 1) ...................................................................4.21

Equation 4.9

CO2 emissions from iron & steel production (Tier 2)..........................................................4.22

Equation 4.10 CO2 emissions from sinter production (Tier 2) ...................................................................4.22
Equation 4.11 CO2 emissions from direct reduced iron production (Tier 2) ..............................................4.23
Equation 4.12 CH4 emissions from sinter production (Tier 1) ...................................................................4.24
Equation 4.13 CH4 emissions from blast furnace production of pig iron (Tier 1) ......................................4.24
Equation 4.14 CH4 emissions from direct reduced iron production (Tier 1) ..............................................4.24
Equation 4.15 CO2 emissions for ferroalloy production by the Tier 1 method...........................................4.33
Equation 4.16 CO2 emissions for ferroalloy production by Tier 2 method.................................................4.33
Equation 4.17 CO2 emissions for ferroalloy productiion by Tier 3 method ...............................................4.34
Equation 4.18 CH4 emissions for ferroalloy production by the Tier 1 method...........................................4.36
Equation 4.19 Carbon contents of ferroalloy reducting agents ...................................................................4.38
Equation 4.20 Process CO2 emissions from anode and/or paste consumption (Tier 1 method) .................4.45
Equation 4.21 CO2 emissions from prebaked anode consumption (Tier 2 and Tier 3 methods) ................4.45
Equation 4.22 CO2 emissions from pitch volatiles combustion (Tier 2 and Tier 3 methods).....................4.46
Equation 4.23 CO2 emissions from bake furnace packing material (Tier 2 and Tier 3 methods)...............4.46
Equation 4.24 CO2 emissions from paste consumption (Tier 2 and Tier 3 methods) .................................4.46
Equation 4.25 PFC emissions (Tier 1 method) ...........................................................................................4.51
Equation 4.26 PFC emissions by Slope method (Tier 2 and Tier 3 methods) ............................................4.51
Equation 4.27 PFC emissions by Overvoltage method (Tier 2 and Tier 3 methods)..................................4.52
Equation 4.28 CO2 emissions from primary magnesium production (Tier 1) ............................................4.61

2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Volume 3: Industrial Processes and Product Use

Equation 4.29 CO2 emissions from primary magnesium production (Tier 2) ............................................4.61
Equation 4.30 SF6 emissions from magnesium casting (Tier 1) .................................................................4.62
Equation 4.31 SF6 emissions from magnesium casting (Tier 2) .................................................................4.62
Equation 4.32 CO2 emissions from lead production...................................................................................4.72
Equation 4.33 CO2 emissions from zinc production (Tier 1)......................................................................4.79
Equation 4.34 CO2 emissions from zinc production (Tier 1)......................................................................4.79

FiguresFigure 4.1

Illustration of main processes for integrated iron and steel production ...............................4.10

Figure 4.2

Illustration of coke production process (emissions reported in Category 1A of the Energy
Sector) .................................................................................................................................4.13

Figure 4.3

Illustration of sinter production process ..............................................................................4.14

Figure 4.4

Illustration of pig iron production processes .......................................................................4.15

Figure 4.5

Illustration of steel production processes.............................................................................4.16

Figure 4.6

Estimation of CO2 emissions from metallurgical coke production......................................4.19

Figure 4.7

Decision tree for estimation of CO2 emissions from iron and steel production...................4.20

Figure 4.8

Decision tree for estimation of CH4 emissions from iron and steel production...................4.20

Figure 4.9

Decision tree for estimation of CO2 emissions from ferroalloy production ........................4.35

Figure 4.10

Decision tree for estimation of CH4 emissions from FeSi and Si alloy production.............4.36

Figure 4.11

Decision tree for calculation of CO2 emissions from primary aluminium production ........4.44

Figure 4.12

Decision tree for calculation of PFC emissions from primary aluminium production ........4.53

Figure 4.13

Decision tree for estimation of CO2 emissions from raw materials calcination in the primarymagnesium production process ...........................................................................................4.63

Figure 4.14

Decision tree for estimation of SF6 emissions from magnesium processing .......................4.64

Figure 4.15

Decision tree for estimation of CO2 emissions from lead production .................................4.72

Figure 4.16

Decision tree for estimation of CO2 emissions from zinc production .................................4.81

Tables

4.6

Table 4.1

Tier 1 default CO2 emission factors for coke production and iron & steel production........4.25

Table 4.2

Tier 1 default CH4 emission factors for coke production and iron & steel production........4.26

Table 4.3

Tier 2 material-specific carbon contents for iron & steel and coke production...................4.27

Table 4.4

Uncertainty ranges...............................................................................................................4.30

Table 4.5

Generic CO2 emission factors for ferroalloy production (tonnes CO2/tonne product) ........4.37

Table 4.6

CO2 emission factors for ferroalloy production (tonnes CO2/tonne reducing agent)...........4.38

Table 4.7

Default emission factors for CH4 (kg CH4/tonne product) ..................................................4.39

Table 4.8

Emission factors for CH4 (kg CH4/tonne product) ..............................................................4.39

Table 4.9

Uncertainty ranges...............................................................................................................4.40

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Metal Industry Emissions

Table 4.10

Tier 1 technology specific emission factors for calculating carbon dioxide emissions fromanode or paste consumption ................................................................................................4.47

Table 4.11

Data sources and uncertainties for parameters used in Tier 2 or 3 method for CO2 emissions
from prebake cells (CWPB and SWPB) ..............................................................................4.48

Table 4.12

Data sources and uncertainties for parameters used in Tier 2 or 3 method for CO2 emissions
from pitch volatiles combustion (CWPB and SWPB)........................................................4.48

Table 4.13

Data sources and uncertainties for parameters used in Tier 2 or 3 method for CO2 emissions
from bake furnace packing material (CWPB and SWPB)..................................................4.48

Table 4.14

Data sources and uncertainties for parameters used in Tier 2 or 3 method for CO2 emissions
from Søderberg cells (VSS and HSS)..................................................................................4.49

Table 4.15

Default emission factors and uncertainty ranges for the calculation of PFC emissions fromaluminium production by cell technology type (Tier 1 method) .........................................4.54

Table 4.16

Technology specific slope and overvoltage coefficients for the calculation of PFC emissions
from aluminium production (Tier 2 method).......................................................................4.54

Table 4.17

Good practice reporting information for calculating CO2 and PFC emissions from aluminium
production by tier ................................................................................................................4.58

Table 4. 18

Possible GHG emissions related to production and processing of magnesium ...................4.59

Table 4.19

Emission factors for ore-specific primary Mg metal production.........................................4.65

Table 4.20

SF6 emission factors for magnesium casting processes (Tier 1).........................................4.66

Table 4.21

Generic CO2 emission factors for lead production by source and furnace type ..................4.73

Table 4.22

Material-specific carbon content for lead production..........................................................4.74

Table 4.23

Uncertainty ranges...............................................................................................................4.76

Table 4.24

Tier 1 CO2 emission factors for zinc production .................................................................4.80

Table 4.25

Uncertainty Ranges .............................................................................................................4.82

Boxes
Box 4.1

Definitions for words/symbols used in equations in this section.........................................4.33

Box 4.2

Anode effect description......................................................................................................4.50

2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Volume 3: Industrial Processes and Product Use

4 METAL INDUSTRY EMISSIONS
4.1

INTRODUCTION

The following sections 4.2 through 4.7 give guidance for estimating greenhouse gas emissions that result fromthe production of metals.
•

Section 4.2 covers emissions from iron and steel, and metallurgical coke production;•

Section 4.3 covers emissions from ferroalloy production;•

Section 4.4 covers emissions from aluminium production;•

Section 4.5 covers emissions from magnesium production;•

Section 4.6 covers emissions from lead production;•

Section 4.7 covers emissions from zinc production.

Care should be exercised to avoid double counting of carbon dioxide (CO2) emissions in both this chapter and in
Volume 2 on Energy Sector, or, in omitting CO2 emissions since CO2 emissions resulting from carbon’s role asprocess reactant and as a heat source to drive the chemical reactions involved in the metallurgical processes areclosely related in many cases. Should CO2 capture technology be installed at a metals production facility, theCO2 captured should be deducted in a higher tier emissions calculation. Any methodology taking into accountCO2 capture should consider that CO2 emissions captured in the process may be both combustion and processrelated. In cases where combustion and process emissions are to be reported separately, e.g., for iron and steel
production, inventory compilers should ensure that the same quantities of CO2 are not double counted. In thesecases the total amount of CO2 captured should preferably be reported in the corresponding energy combustion
and IPPU source categories in proportion to the amounts of CO2 generated in these source categories. The
default assumption is that there is no CO2 capture and storage (CCS) taking place. For additional information on
CO2 capture and storage refer to Volume 3, Section 1.2.2 and for more details to Volume 2, Section 2.3.4.

4.8

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Metal Industry Emissions

4.2

IRON & STEEL AND METALLURGICAL COKE
PRODUCTION

The production of iron and steel leads to emissions of carbon dioxide (CO2), methane (CH4), and nitrous oxide(N2O). This chapter provides guidance for estimating emissions of CO2 and CH4.1
The iron and steel industry broadly consists of:•Primary facilities that produce both iron and steel;•

Secondary steelmaking facilities;•

Iron production facilities; and•Offsite production of metallurgical coke.

Figure 4.1 illustrates the main processes for iron and steel production: metallurgical coke production, sinterproduction, pellet production, iron ore processing, iron making, steelmaking, steel casting and very often
combustion of blast furnace and coke oven gases for other purposes. The main processes may occur under what
is referred to as an ‘integrated’ facility and typically include blast furnaces, and basic oxygen steelmaking
furnaces (BOFs), or in some cases open hearth furnaces (OHFs). It is also common for parts of the production to
be offsite under the responsibility of another operator such as an offsite coke production facility.
In some countries, there will be coke production facilities that are not integrated with iron and steel production(i.e., ‘offsite’). This chapter provides guidance for estimating emissions of CO2 and CH4 from all cokeproduction to ensure consistency and completeness. Countries should estimate emissions from onsite and offsite
coke production separately under higher tiers as the by-products of onsite coke production (e.g., coke oven gas,coke breeze, etc.) are often used during the production of iron and steel.
P r imary and s eco nda ry st ee l- making:Steel production can occur at integrated facilities from iron ore, or at secondary facilities, which produce steel
mainly from recycled steel scrap. Integrated facilities typically include coke production, blast furnaces, and basic
oxygen steelmaking furnaces (BOFs), or in some cases open hearth furnaces (OHFs). Raw steel is produced
using a basic oxygen furnace from pig iron produced by the blast furnace and then processed into finished steel
products. Pig iron may also be processed directly into iron products. Secondary steelmaking most often occurs
in electric arc furnaces (EAFs). In 2003, BOFs accounted for approximately 63 percent of world steel production
and EAFs approximately accounted for 33 percent; OHF production accounted for the remaining 4 percent but istoday declining.
Iro n product ion:
Iron production can occur onsite at integrated facilities or at separate offsite facilities containing blast furnaces
and BOFs. In addition to iron production via blast furnace, iron can be produced through a direct reduction
process. Direct reduction involves the reduction of iron ore to metallic iron in the solid state at processtemperatures less than 1000°C.
M eta llu rg ica l cok e prod uc tio n:
Metallurgical coke production is considered to be an energy use of fossil fuel, and as a result emissions should
be reported in Category 1A of the Energy Sector. The methodologies are presented here in Volume 3, however,
because the activity data used to estimate emissions from energy and non-energy in integrated iron and steel
production have significant overlap. All fuel consumed in this source category not allocated as inputs to thesinter plants, pelletisation plants and blast furnace should be regarded as fuel combustion, which is dealt withand reported in the Energy Sector (see Volume 2: Energy).

1

No methodologies are provided for N2O emissions. These emissions are likely to be small, but countries can calculate
estimates provided they develop country-specific methods based on researched data.

2006 IPCC Guidelines for National Greenhouse Gas Inventories

4.9

Pelletizing
Plant

Sinter Plant

Coke Plant

Blast furnace
pig ironproduction

Pig IrontoIron Processing

Coke Oven Gas

Steelmaking[Basic Oxygen
Furnace]

Basic Oxygen
Furnace Gas

Steel
to
Steel Processing* Modified from: European Conference on "The Sevilla Process: A Driver for Environmental Performance in Industry" Stuttgart, 6 and 7 April 2000, BREF on the Production of Iron and Steel conclusion on BAT, Dr. Harald Schoenberger, Regional State Governmental Office Freiburg, April 2000. (Schoenberger, 2000)

Coal
Injection

Iron Ore.
Additives

Iron Ore.
Additives

Coke
BreezeCoking
Coal

Illustration of main processes for integrated iron and steel production*

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Figure 4.1

Volume 3: Industrial Processes and Product Use

4.10

Chapter 4: Metal Industry Emissions

4.2.1

Introduction

METALLURGICAL COKE PRODUCTION
Metallurgical coke is primarily used in the blast furnace to make iron. Coke is also used in other metallurgicalprocesses, such as the manufacture of cast iron, ferroalloys, lead, and zinc, and in kilns to make lime andmagnesium. Metallurgical coke is the solid product obtained from the carbonisation of coal, principally coking
coal, at high temperature. It is low in moisture content and volatile matter. Coking coal refers to bituminous coalwith a quality that allows the production of a coke suitable to support a blast furnace charge. Its gross calorificvalue is greater than 23 865 kJ/kg (5 700 kcal/kg) on an ash-free but moist basis. Coke oven gas is a by-productof the manufacture of metallurgical coke for the production of iron and steel. Figure 4.2 illustrates the cokeproduction process and associated sources of CH4 and CO2 emissions.
Note that coke oven gas may be burned to heat coke ovens or transferred onsite in an integrated iron and steel
plant and used in sinter production or iron production processes. Coke oven gas may also be transferred off site
(e.g., into the natural gas distribution system) and used as an energy source. The combustion of coke in blast
furnaces during the iron and steel-making process produces blast furnace gas, which may then be recovered andtransferred from the iron and steel mill to the onsite coke plant and burned to heat coke ovens or used in sinterproduction. The combustion of blast furnace gas and coke oven gas is the main sources of CO2 and CH4
emissions in coke production.

SINTER PRODUCTION
Iron ore and other iron-containing materials may be agglomerated in sinter plants at integrated iron and steel
plants prior to introduction into the blast furnace. Feedstock to sinter plants may include fine iron ores, additives(e.g., lime, olivine), and iron-bearing recycled materials from downstream iron and steelmaking processes (e.g.,
dust from blast-furnace gas cleaning). Coke breeze (small-grade coke oven coke with particle sizes of < 5 mm) is
the most commonly used process material in sinter plants. The coke breeze may be produced from the onsite
coke ovens in integrated iron and steel plants, or may be purchased from offsite coke producers. Blast furnace
gas or coke oven gas produced onsite during integrated iron and steel production may be used in sinter plants.
Operation of sinter plants produces carbon dioxide emissions from oxidation of the coke breeze and other inputs.
Off gas from sinter production also contains methane and other hydrocarbons. Figure 4.3 illustrates the sinterproduction process.

PELLET PRODUCTION
Pellets are formed from iron-containing raw materials (i.e., fine ore and additives) into 9-16 mm spheres in avery high temperature process. The process includes grinding, drying, balling, and thermal treatment of the raw
materials. Pelletisation plants are principally located at iron mines or at shipping ports, but can also be locatedonsite as part of an integrated iron and steel facility. Natural gas or coal may be used as fuel for pelletisation
plants; for pelletisation plants located onsite at an integrated iron and steel facility, coke oven gas may be used asa fuel. Energy consumption for the process and the associated CO2 emissions will depend in part on the qualityof the iron ore and other raw materials used in the process. The CO2 emissions will also depend upon the carbon
contents and heating values of fuels used in the process.

IRONMAKING AND THE ROLE OF COKE
Most CO2 emitted by the iron and steel industry is associated with the production of iron, more specifically theuse of carbon to convert iron ore to iron. Figure 4.4 describes the iron-making process and associated sources ofemissions. Carbon is supplied to the blast furnace mainly in the form of coke produced from metallurgical grade
coking coal (but can also be in the form charcoal made from wood or other forms of carbon.). Carbon serves adual purpose in the iron making process, primarily as a reducing agent to convert iron oxides to iron, but also as
an energy source to provide heat when carbon and oxygen react exothermically. Blast furnace gas is produced
during the combustion of coke in blast furnaces. It is typically recovered and used as a fuel partly within theplant and partly in other steel industry processes, or in power stations equipped to burn it. Blast furnace gas may
also be recovered and transferred from the iron and steel mill to the onsite coke plant and burned for energy
within the coke ovens. Blast furnace gas may also be transferred offsite and used as an energy source bothwithin the furnace and when blast furnace gas is combusted to heat blast air. Oxygen steel furnace gas is
obtained as a by-product of the production of steel in a basic oxygen furnace (BOF) and is recovered on leaving
the furnace. All carbon used in blast furnaces should be considered process-related IPPU emissions.
Additionally, iron can be produced through a direct reduction process. Direct reduction involves the reduction ofiron ore to metallic iron in the solid state at process temperatures less than 1 000°C. A solid product referred toas direct reduced iron (DRI) is produced by the direct reduction process. DRI has a carbon content of < 2 percent.
DRI is normally used as a replacement for scrap metal in the electric arc furnace steelmaking route, but may also

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Volume 3: Industrial Processes and Product Use

be used as a feedstock for blast furnace iron making. DRI may also be melted into briquettes, referred to as hot
briquetted iron (HBI), when the product has to be stored or transported. Inventory preparers can estimate the CO2
emissions from these processes from the energy consumption and carbon content of the fuel (e.g., natural gas,coal).

STEELMAKING
Steel production in a BOF begins by charging the vessel with 70-90 percent molten iron and 10-30 percent steel
scrap. High purity oxygen then combines with the carbon in the iron to create an exothermic reaction that melts
the charge while lowering the carbon content. Iron from the blast furnace usually contains 3-4 percent carbon,
which must be reduced to less than 1 percent, refined, and alloyed to produce the desired grade of steel.
Steel production in an EAF typically occurs by charging 100 percent recycled steel scrap, which is melted using
electrical energy imparted to the charge through carbon electrodes and then refined and alloyed to produce thedesired grade of steel. Although EAFs may be located in integrated plants, typically they are stand-alone
operations because of their fundamental reliance on scrap and not iron as a raw material. Since the EAF process
is mainly one of melting scrap and not reducing oxides, carbon’s role is not as dominant as it is in the blast
furnace/BOF process. In a majority of scrap-charged EAF, CO2 emissions are mainly associated with
consumption of the carbon electrodes. All carbon used in EAFs and other steelmaking processes should beconsidered process-related IPPU emissions. Figure 4.5 illustrates the steel making process and associated sourcesof emissions.

4.12

2006 IPCC Guidelines for National Greenhouse Gas Inventories

By-product fuels from
Integrated Iron and Steel(e.g., Blast Furnace Gas)

Coke Oven Heating

Coke
Oven Process

COG burned
on I&S site

Coal Tars andLight Oils

Coke Oven
Gas and otherby-products

Coke Oven
Gas (COG)

BreezeMetallurgical
Coke

Used Onsite in Blast
Furnace or other
Integrated Iron andSteel Process

COG
transferred
Off SiteTransferred
Off SiteUse Onsite(e.g., Sinter Plants)
or Off Site

Note:
Bold lines apply only to Onsite Coke Production at Integrated Iron and Steel Mill. Dashed lines apply to transfers of materials to ‘Off Site processes.’ ‘Off Site process’ does not include
Integrated Iron and Steel production processes, which are categorised as Onsite.

Metallurgical
Coal and otherprocess carbon

CO2 and CH4
emissions

Illustration of coke production process (emissions reported in Category 1A of the Energy Sector)

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Figure 4.2

4.13

Chapter 4: Metal Industry Emissions

Iron Ore

Coke
BreezeNatural
Gas

Other
Waste
Gas

Illustration of sinter production process

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Figure 4.3

Volume 3: Industrial Processes and Product Use

Coke
Oven
Gas

Sintering
Process

CH4 Emissions
CO2 Emissions

Blast
Furnace
Gas

Sinterto
Blast Furnace Pig
Iron Production

4.14

From
Integrated
Coke
Oven

Purchased
Coke

Integrated
Coke Oven -Coke Oven Gas

Integrated Coke Oven-- Coke

Scrap Iron

*Coal Tar,
Light Oil,
BreezeBlast
Furnace

Slag

Coal

Transferred
Off Site

Pig IronTar, OilTransferred
to Steel Mill

Integrated
Coke Oven -By-products*

Iron Ore,
Pellets,
SinterIllustration of pig iron production processes

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Figure 4.4

DolomiteTransferred
Off SiteTransferred toIntegrated
Coke Oven

Limestone

Direction of Process
Connects to Steel Production
Connects to an External Process
Process
Byproduct
Raw Material
Product

Burned Onsite
within iron andsteel process

Blast Furnace Gas

CH4 Emissions
CO2 Emissions

NaturalGas

4.15

Chapter 4: Metal Industry Emissions

Iron
Ore

NaturalGas

EAF
ChargeCarbon

EAF Steel

SlagElectric Arc
Furnace (EAF)

DirectReduced/Hot Briquetted

Pig Iron

CH4 Emissions
CO2 Emissions

Direct Reduced/
Hot Briquetted

EAF
Anode

CH4 Emissions
CO2 Emissions

Waste
Gas

Illustration of steel production processes

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Figure 4.5

Volume 3: Industrial Processes and Product Use

Tar

Slag

Basic Oxygen
Furnace (BOF)

CH4 Emissions
CO2 Emissions

Limestone

BOF Steel

Fuel Oil

Scrap
Steel

Other
non-fuel C
additions

Slag

Open Hearth
Furnace (OHF)

CH4 Emissions
CO2 Emissions

OHF Steel

Dolomite

4.16

Chapter 4: Metal Industry Emissions

4.2.2
4.2.2.1

Methodological issues
C HOICE OF METHOD : METALLURGICAL C O K E P R O D U C T I O N

The IPCC Guidelines outline three tiers for calculating CO2 emissions and two tiers for calculating CH4emissions from coke production. The choice of a good practice method for estimation of CO2 emissions depends
on national circumstances as shown in the decision tree in Figure 4.6 Estimation of CO2 Emissions from
Metallurgical Coke Production. For CH4 emissions, use the decision tree in Figure 4.8.
Metallurgical coke is produced either at the iron and steel facility (‘onsite’) or at separate facilities (‘offsite’).The
Tier 1 method calculates emissions from all coke production using default emission factors applied to nationalcoke production.
The Tier 2 method for estimating CO2 emissions distinguishes between onsite and offsite coke production. It
uses national activity data for the consumption and production of process materials (e.g., coking coal consumed,coke produced, and coal tar products produced). As discussed above, the Tier 2 method is not applicable toestimating CH4 emissions. The Tier 3 method requires plant-specific CO2 emissions data and plant-specific CH4
emissions data, or plant-specific activity data.

TIER 1 METHOD – PRODUCTION-BASED EMISSION FACTORS
Equation 4.1 calculates emissions from all coke production. The Tier 1 method assumes that all coke madeonsite at iron and steel production facilities is used onsite. The Tier 1 method is to multiply default emission
factors by tonnes of coke produced. Emissions should be reported in the Energy Sector.
EQUATION 4.1
EMISSIONS FROM COKE PRODUCTION (TIER 1)
E CO 2 = Coke • EFCO 2 and E CH 4 = Coke • EFCH 4 (To be reported in Energy Sector)
Where:
ECO2 or ECH4 = emissions of CO2 or CH4 from coke production, tonnes CO2 or tonnes CH4
Coke = quantity of coke produced nationally, tonnes
EF= emission factor, tonnes CO2/tonne coke production or tonnes CH4/tonne coke production
Note: The Tier 1 method assumes that all of the coke oven by-products are transferred off site and that allof the coke oven gas produced is burned on site for energy recovery.

TIER 2 METHODThe Tier 2 method is appropriate if national statistics on process inputs and outputs from integrated and nonintegrated coke production processes are available. Tier 2 will produce a more accurate estimate than Tier 1
because it takes into account the actual quantity of inputs into and outputs rather than making assumptions.
As expressed in Equations 4.2 and 4.3, Tier 2 estimates CO2 emissions from onsite coke production separatelyfrom off-site production. This separation is due to overlapping data requirements when estimating emissions
from onsite coke production and emissions from iron and steel production.
EQUATION 4.2
CO2 EMISSIONS FROM ONSITE COKE PRODUCTION (TIER 2)⎡
E CO 2, energy = ⎢CC • C CC + ∑ (PM a • C a ) + BG • C BGa⎣
⎤ 44
− CO • C CO − COG • C COG − ∑ (COB b • C b )⎥ •b
⎦ 12

Where:
ECO2, energy = emissions of CO2 from onsite coke production to be reported in Energy Sector, tonnes

2006 IPCC Guidelines for National Greenhouse Gas Inventories

4.17

Volume 3: Industrial Processes and Product Use

CC = quantity of coking coal consumed for coke production in onsite integrated iron and steel production
facilities, tonnes
PMa = quantity of other process material a, other than those listed as separate terms, such as natural gas,and fuel oil, consumed for coke and sinter production in onsite coke production and iron and steel
production facilities, tonnes
BG = quantityof blast furnace gas consumed in coke ovens, m3 (or other unit such as tonnes or GJ.
Conversion of the unit should be consistent with Volume 2: Energy)
CO = quantity of coke produced onsite at iron and steel production facilities, tonnes
COG = quantity of coke oven gas transferred offsite , m3 (or other unit such as tonnes or GJ. Conversionof the unit should be consistent with Volume 2: Energy)
COBb = quantity of coke oven by-product b, transferred offsite either to other facilities, tonnes
Cx = carbon content of material input or output x, tonnes C/(unit for material x) [e.g., tonnes C/tonne]
For offsite coke production, the inventory compiler should use Equation 4.3. Total emissions are the sum ofemissions from all plants using both Equations 4.2 and 4.3.
EQUATION 4.3
CO2 EMISSIONS FROM OFFSITE COKE PRODUCTION (TIER 2)⎡⎤ 44
E CO 2,energy = ⎢CC • C CC + ∑ (PM a • C a ) − NIC • C NIC − COG • C COG − ∑ (COBb • C b )⎥ •
a
b
⎣
⎦ 12

Where:
ECO2, energy = emissions of CO2 from offsite coke production to be reported in Energy Sector, tonnes
CC = quantity of coking coal used in non-integrated coke production facilities, tonnes
PMa = quantity of other process material a, other than coking coal, such as natural gas, and fuel oil
consumed nationally in non-integrated coke production, tonnes
NIC = quantity of coke produced offsite in non-integrated coke production facilities nationally, tonnes
COG = quantity of coke oven gas produced in offsite non-integrated coke production facilities nationallythat is transferred to other facilities, m3 (or other unit such as tonnes or GJ. Conversion of the unit
should be consistent with Volume 2: Energy)
COBb= quantity of coke oven by-product b, produced nationally in offsite non-integrated facilities andtransferred offsite to other facilities, tonnes
Cx = carbon content of material input or output x, tonnes C/(unit for material x) [e.g., tonnes C/tonne]

TIER 3 METHOD
Unlike the Tier 2 method, the Tier 3 method uses plant specific data because plants can differ substantially intheir technology and process conditions. If actual measured CO2/CH4 emissions data are available from onsite
and offsite coke production plants, these data can be aggregated and used directly to account for nationalemissions from metallurgical coke production using the Tier 3 method. Total national emissions will equal thesum of emissions reported from each facility. If facility-specific CO2 emissions data are not available, CO2
emissions can be calculated from plant-specific activity data applying the Tier 2 method, Equations 4.2 and 4.3.
Total national emissions will equal the sum of emissions reported from each facility.

4.18

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Metal Industry Emissions

Figure 4.6

Estimation of CO 2 emissions from metallurgical coke production
Start

Are
plant-specificemissions or activity data
available?

Yes

Use or Calculate emissions
using plant-specific emissions
data or activity data.
Box 3: Tier 3

NoAre
activity data
available for onsite and offsite
coke production?

Yes

Calculate emissions from cokeproduction using material
specific carbon contents.
Box 2: Tier 2

No
Assume all coke is produced onsite,using default emission factors andnational production data.
Box 1: Tier 1

4.2.2.2

C HOICE OF METHOD : IRON AND STEEL PRODUCTION

These Guidelines outline three tiers for calculating CO2 emissions and two tiers for calculating CH4 emissions
from iron and steel production. The choice of a good practice method depends on national circumstances asshown in the decision tree in Figure 4.7 for CO2 emissions and Figure 4.8 for CH4 emissions: Decision Tree for
Estimation of CO2 Emissions from Iron & Steel Production and Decision Tree for Estimating of CH4 Emissions
from Iron and Steel Production. The Tier 1 method is based on national production data and default emission
factors. It may lead to errors due to its reliance on assumptions rather than actual data for the quantity of inputs
into the sinter production and iron and steel production sector that contribute to CO2 emissions. Therefore, theTier 1 is appropriate only if iron and steel production is not a key category. Default emission factors are provided
for sinter production, blast furnace iron making, direct reduced iron production, pellet production, and eachmethod of steelmaking. The primary sources of emissions are the blast furnace iron making, and steelmaking.
The Tier 2 method for estimating CO2 emissions from iron and steel production is based on data for the known
consumption of raw materials, including reducing agents, and industry-wide data. It uses a mass balance
approach and material-specific carbon contents. The Tier 2 method is not applicable to estimating CH4emissions. The Tier 3 method requires plant-specific emissions or activity data aggregated to the national levelfor estimating CO2 and CH4 emissions.

2006 IPCC Guidelines for National Greenhouse Gas Inventories

4.19

Volume 3: Industrial Processes and Product Use

Figure 4.7

Decision tree for estimation of CO 2 emissions from iron and steel production
Start

Are
plant-specificemissions or activity data
available?

Yes

Use or calculate
emissions using plant
specific data.
Box 3: Tier 3

No
Are national
process materials data
available?

Yes

Calculate emissions
using material-specificcarbon contents.
Box 2: Tier 2

No

Is this a key
category1?

Calculate emissions
using default emission
factors and national
production data.

No

Box 1: Tier 1

Yes
Collect data for the Tier 3or the Tier 2 method.

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.

Figure 4.8

Decision tree for estimation of CH 4 emissions from iron and steel production
Start

Are
plant-specific emissions or activity
data available?

Yes

Use or calculate
emissions using plant
specific data.
Box 2: Tier 3

No
Is this a key
category1?
YesNo

Calculate emissions
using default emission
factors and national
production data.
Box 1: Tier 1

Collect data for the
Tier 3 method.
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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2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Metal Industry Emissions

METHODOLOGY FOR ESTIMATING CO 2 EMISSIONS
Tier 1 method – production-based emission factors
The Tier 1 approach for emissions from iron and steel production is to multiply default emission factors bynational production data, as shown in Equation 4.4. Because emissions per unit of steel production vary widely
depending on the method of steel production, it is good practice to determine the share of steel produced indifferent types of steelmaking processes, calculate emissions for each process, and then sum the estimates.
Equation 4.4 considers steel production from Basic Oxygen Furnaces (BOF), Electric Arc Furnaces (EAF), andOpen Hearth Furnaces (OHF). In the event that activity data for steel production for each process is not available,
default allocation of total national steel production among these three steelmaking processes is provided in Table
4.1 in Section 4.2.2.3.
Equation 4.5 calculates emissions from pig iron production that is not converted into steel. It is preferable toestimate emissions from this production separately because the emission factors for integrated iron and steel
production (BOF and OHF processes) take into account emissions from both steps.
Equation 4.6 calculates CO2 emissions from production of Direct Reduced Iron (DRI) for the Tier 1 method
using a CO2 emission factor.
It is also good practice to estimate separately the emissions from sinter production and national pellet production,using Equations 4.7 and 4.8. Equations 4.7 and 4.8 should be used if the inventory compiler does not havedetailed information about the process materials used. If the process materials are known, emissions should be
calculated using the Tier 2 method.
Total emissions are the sum of Equations 4.4 to 4.8.
EQUATION 4.4
CO2 EMISSIONS FROM IRON AND STEEL PRODUCTION (TIER 1)
Iron & Steel: E CO 2, non − energy = BOF • EFBOF + EAF • EFEAF + OHF • EFOHF

EQUATION 4.5
CO2 EMISSIONS FROM PRODUCTION OF PIG IRON NOT PROCESSED INTO STEEL (TIER 1)
Pig Iron Production: E CO 2, non −energy = IP • EFIPEQUATION 4.6
CO2 EMISSIONS FROM PRODUCTION OF DIRECT REDUCED IRON (TIER 1)
Direct Reduced Iron: E CO 2, non − energy = DRI • EFDRIEQUATION 4.7
CO2 EMISSIONS FROM SINTER PRODUCTION (TIER 1)
Sinter Production: E CO 2, non −energy = SI • EFSIEQUATION 4.8
CO2 EMISSIONS FROM PELLET PRODUCTION (TIER 1)
Pellet Production: E CO 2, non − energy = P • EFP
Where:
ECO2, non-energy = emissions of CO2 to be reported in IPPU Sector, tonnes
BOF= quantity of BOF crude steel produced, tonnes
EAF = quantity of EAF crude steel produced, tonnes
OHF = quantity of OHF crude steel produced, tonnes

2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Volume 3: Industrial Processes and Product Use

IP = quantity of pig iron production not converted to steel, tonnes
DRI = quantity of Direct Reduced Iron produced nationally, tonnes
SI = quantity of sinter produced nationally, tonnes
P = quantity of pellet produced nationally, tonnes
EFx= emission factor, tonnes CO2/tonne x produced

Tier 2 method
The Tier 2 method is appropriate if the inventory compiler has access to national data on the use of processmaterials for iron and steel production, sinter production, pellet production, and direct reduced iron production.
In addition, as discussed in Section 4.2.2.5, there are a number of other process inputs and outputs that could beconsidered under Tier 2. These data may be available from governmental agencies responsible for manufacturing
or energy statistics, business or industry trade associations, or individual iron and steel companies. The Tier 2
method will produce a more accurate estimate than the Tier 1 method because it takes into account the actual
quantity of inputs that contribute to CO2 emissions.
In calculating pellet production emissions, energy consumption and heating value and carbon content of the fuelcan be used similarly to the other methodologies.

EQUATION 4.9
CO2 EMISSIONS FROM IRON & STEEL PRODUCTION (TIER 2)⎡
E CO 2,non − energy = ⎢ PC • C PC + ∑ (COB a • C a ) + CI • C CI + L • C L + D • C D + CE • C CEa⎣⎤ 44
+ ∑ (Ob • C b ) + COG • C COG − S • C S − IP • C IP − BG • C BG ⎥ •b⎦ 12

EQUATION 4.10
CO2 EMISSIONS FROM SINTER PRODUCTION (TIER 2)⎡⎤ 44
E CO 2,non −energy = ⎢CBR • C CBR + COG • C COG + BG • C BG + ∑ (PM a • C a ) − SOG • C SOG ⎥ •a⎣⎦ 12
Where, for iron and steel production:
ECO2, non-energy = emissions of CO2 to be reported in IPPU Sector, tonnes
PC = quantity of coke consumed in iron and steel production (not including sinter production), tonnes
COBa = quantity of onsite coke oven by-product a, consumed in blast furnace, tonnes
CI= quantity of coal directly injected into blast furnace, tonnes
L = quantity of limestone consumed in iron and steel production, tonnes
D = quantity of dolomite consumed in iron and steel production, tonnes
CE = quantity of carbon electrodes consumed in EAFs, tonnes
Ob = quantity of other carbonaceous and process material b, consumed in iron and steel production, suchas sinter or waste plastic, tonnes
COG= quantity of coke oven gas consumed in blast furnace in iron and steel production, m3 (or other unit
such as tonnes or GJ. Conversion of the unit should be consistent with Volume 2: Energy)
S = quantity of steel produced, tonnes
IP = quantity of iron production not converted to steel, tonnes
BG = quantity of blast furnace gas transferred offsite, m3 (or other unit such as tonnes or GJ. Conversionof the unit should be consistent with Volume 2: Energy)
Cx = carbon content of material input or output x, tonnes C/(unit for material x) [e.g., tonnes C/tonne]

4.22

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Metal Industry Emissions

Where, for sinter production:
ECO2, non-energy = emissions of CO2 to be reported in IPPU Sector, tonnes
CBR = quantity of purchased and onsite produced coke breeze used for sinter production, tonnes
COG= quantity of coke oven gas consumed in blast furnace in sinter production, m3 (or other unit such as
tonnes or GJ. Conversion of the unit should be consistent with Volume 2: Energy)
BG = quantity of blast furnace gas consumed in sinter production, m3 (or other unit such as tonnes or GJ.
Conversion of the unit should be consistent with Volume 2: Energy)
PMa = quantity of other process material a, other than those listed as separate terms, such as natural gas,and fuel oil, consumed for coke and sinter production in integrated coke production and iron andsteel production facilities, tonnes
SOG = quantity of sinter off gas transferred offsite either to iron and steel production facilities or otherfacilities, m3 (or other unit such as tonnes or GJ. Conversion of the unit should be consistent with
Volume 2: Energy)
Cx = carbon content of material input or output x, tonnes C/(unit for material x) [e.g., tonnes C/tonne]
Equation 4.11 calculates CO2 emissions from production of direct reduced iron for the Tier 2 method based on
fuel consumption and fuel carbon content. Emissions from DRI production are derived from combusting fuel,coke breeze, metallurgical coke or other carbonaceous materials, and are to be reported as IPPU emissions.
EQUATION 4.11
CO2 EMISSIONS FROM DIRECT REDUCED IRON PRODUCTION (TIER 2)
44
E CO 2,non −energy = (DRI NG • C NG + DRI BZ • C BZ + DRI CK • C CK ) •12

Where:
ECO2, non-energy = emissions of CO2 to be reported in IPPU Sector, tonnes
DRING = amount of natural gas used in direct reduced iron production, GJ
DRIBZ = amount of coke breeze used in direct reduced iron production, GJ
DRICK = amount of metallurgical coke used in direct reduced iron production, GJ
CNG = carbon content of natural gas, tonne C/GJ
CBZ = carbon content of coke breeze, tonne C/GJ
CCK = carbon content of metallurgical coke, tonne C/GJ

Tier 3 method
Unlike the Tier 2 method, the Tier 3 method uses plant specific data. The Tier 3 method provides an even moreaccurate estimate of emission than the Tier 2 method because plants can differ substantially in their technology
and process conditions. If actual measured CO2 emissions data are available from iron and steelmaking facilities,
these data can be aggregated to account for national CO2 emissions. If facility-specific CO2 emissions data are
not available, CO2 emissions can be calculated from plant-specific activity data for individual reducing agents,
exhaust gases, and other process materials and products. Total national emissions will equal the sum ofemissions reported from each facility. Equations 4.9 through 4.11 describe the parameters that are necessary foran accounting of plant-specific emissions using the Tier 3 method and plant-specific activity data at a facility
level. Plant-specific carbon contents for each material are required for the Tier 3 method.

METHODOLOGY FOR CH 4
When carbon-containing materials are heated in the furnace for sinter production or iron production, the volatiles,
including methane, are released. With open or semi-covered furnaces, 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 non-methane
volatile organic compounds (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 falseair) will reduce the content of CH4 further.

2006 IPCC Guidelines for National Greenhouse Gas Inventories

4.23

Volume 3: Industrial Processes and Product Use

This section describes a Tier 1 default method and a more advanced Tier 3 facility-level method for CH4 fromsinter production or iron production, both of which are similar to the approaches described for estimating CO2
emissions. There is no Tier 2 method. CH4 may be emitted from steel–making processes as well, however thoseemissions are assumed to be negligible. Therefore CH4 emissions from steel-making processes are not discussed
here.
The Tier 1 methodology for CH4 is based on emission factors and national production statistics.

EQUATION 4.12
CH4 EMISSIONS FROM SINTER PRODUCTION (TIER 1)
Sinter Production: E CH 4, non −energy = SI • EFSIEQUATION 4.13
CH4 EMISSIONS FROM BLAST FURNACE PRODUCTION OF PIG IRON (TIER 1)
Pig Iron Production: E CH 4, non − energy = PI • EFPIEQUATION 4.14
CH4 EMISSIONS FROM DIRECT REDUCED IRON PRODUCTION (TIER 1)
Direct Reduced Iron Production: E CH 4, non − energy = DRI • EFDRI

Where:
ECH4, non-energy = emissions of CH4 to be reported in IPPU Sector, kg
SI = quantity of sinter produced nationally, tonnes
PI = quantity of iron produced nationally including iron converted to steel and not converted to steel,tonnes
DRI = quantity of direct reduced iron produced nationally, tonnes
EFx = emission factor, kg CH4/tonne x produced
The Tier 3 method uses plant specific emissions data. If actual measured CH4 emissions data are available forcoke production, these data can be aggregated to account for national CH4 emissions. Total national emissions
will equal the sum of emissions reported from each facility.

4.2.2.3

C HOICE OF EMISSION FACTORSTIER 1 METHOD
Carbon dioxide emission factors
Table 4.1 provides default emission factors for coke, sinter, pellet, iron, and steel production. The emission
factors for the three steelmaking methods are based on expert judgment using typical practice for the different
steel production scenarios listed. The default emission factors account for all carbon input into the blast furnace.
It is assumed based on the Integrated Pollution Prevention and Control (IPPC) Reference Document on
Production of Iron and Steel (European IPPC Bureau, 2001) (referred to in this section as ‘IPPC I&S BAT
Document’) that most of the carbon input to the blast furnace is from coke (60 -90 percent).
The default CO2 emission factor for coke production is derived by averaging plant-specific CO2 emissions datafor 11 European coke plants reported in the IPPC I&S BAT Document. Emissions of CO2 are reported in Table
6.2 of the IPPC I&S BAT Document in units of kilograms of CO2 per tonne of liquid steel produced. The CO2
emissions range from 175 to 200 kg CO2 per tonne liquid steel. The conversion factors provided in Table 6.2 ofthe IPPC Document are 940 kg pig iron per tonne liquid steel and 358 kg coke per tonne pig iron. Based on theseconversion factors the average CO2 emissions from the 11 European coke plants is 0.56 tonne CO2 per tonnecoke produced.
The CO2 emission factor for sinter plants is derived by averaging plant-specific CO2 emissions data for four
European sinter plants reported in the IPPC I&S BAT Document. Emissions of CO2 are reported in Table 4.1 of

4.24

2006 IPCC Guidelines for National Greenhouse Gas Inventories

Chapter 4: Metal Industry Emissions

the IPPC I&S BAT Document in units of kilograms of CO2 per tonne of liquid steel produced. The CO2
emissions range from 205 to 240 kg CO2 per tonne liquid steel. The conversion factors provided in Table 4.1 ofthe IPPC I&S BAT Document are 940 kg pig iron per tonne liquid steel and 1160 kg sinter per tonne pig iron.
Based on these conversion factors the average CO2 emissions from the four European sinter plants is 0.2 kg CO2
per kg sinter produced.
The CO2 emission factor for blast furnace iron making is derived by averaging plant-specific CO2 emissions data
for European sinter plants reported in the IPPC I&S BAT Document. The CO2 and CO content of blast furnace
gas produced by the iron making process is reported in Tables 7.2 and 7.3 of the IPPC I&S BAT Document inunits of kilograms of CO2 per tonne of pig iron produced and kilograms of CO per tonne of pig iron produced.
The CO2 content ranges from 400 to 900 kg CO2 per tonne pig iron produced and the CO content ranges from
300 to 700 kg CO per tonne of pig iron produced. Based on the assumption that all of the blast furnace gas
burned for energy recovery (and combusted to CO2) within the integrated iron and steel mill and that no blast
furnace gas is transferred off site, this corresponds to an emission factor of 1.35 kg CO2 per kg pig iron produced.

TABLE 4.1
TIER 1 DEFAULT CO2 EMISSION FACTORS FOR COKE PRODUCTION AND IRON & STEEL PRODUCTION
Process

Emission Factor

SourceSinter Production (tonne CO2 per
tonne sinter produced)

0.20

Sinter Production: European IPPC Bureau (2001), Integrated Pollution
Prevention and Control (IPPC) Best Available Techniques Reference
Document on the Production of Iron and Steel, December 2001, Table
4.1, Page 29. http://eippcb.jrc.es/pages/FActivities.htm

Coke Oven (tonne CO2 per tonnecoke produced)

0.56

Coke Production: European IPPC Bureau (2001), Integrated Pollution
Prevention and Control (IPPC) Best Available Techniques Reference
Document on the Production of Iron and Steel, December 2001, Table
6.2, Page 122. http://eippcb.jrc.es/pages/FActivities.htm

Iron Production (tonne CO2 per
tonne pig iron produced)

1.35

Iron Production: European IPPC Bureau (2001), Integrated Pollution
Prevention and Control (IPPC) Best Available Techniques Reference
Document on the Production of Iron and Steel, December 2001, Tables
7.2 and 7.3. http://eippcb.jrc.es/pages/FActivities.htm

Direct Reduced Iron production(tonne CO2 per tonne DRI
produced)

0.70

Direct Reduced Iron Production: European IPPC Bureau (2001),
Integrated Pollution Prevention and Control (IPPC) Best Available
Techniques Reference Document on the Production of Iron and Steel,
December 2001, Table 10.1 Page 322 and Table 10.4 Page 331.
http://eippcb.jrc.es/pages/FActivities.htm

Pellet production (tonne CO2 per
tonne pellet produced)

0.03

Pellet Production: European IPPC Bureau (2001), Integrated Pollution
Prevention and Control (IPPC) Best Available Techniques Reference
Document on the Production of Iron and Steel, December 2001, Table
5.1 Page 95. http://eippcb.jrc.es/pages/FActivities.htm

Steelmaking Method
Basic Oxygen Furnace (BOF)(tonne CO2 per tonne of steel
produced)

1.46

Electric Arc Furnace (EAF)(tonne CO2 per tonne of steel
produced) **0.08

Open Hearth Furnace (OHF)(tonne CO2 per tonne of steel
produced)

1.72

Global Average Factor (65%
BOF, 30% EAF, 5% OHF)*(tonne CO2 per tonne of steel
produced)

Steel Production: Consensus of experts and IISI Environmental
Performance Indicators 2003 STEEL(International Iron and Steel Institute, 2004)
Steel Production: Consensus of experts and IISI Environmental
Performance Indicators 2003 STEEL(International Iron and Steel Institute, 2004)
Steel Production: Consensus of experts and IISI Environmental
Performance Indicators 2003 STEEL(International Iron and Steel Institute, 2004)

1.06

Steel Production: Consensus of experts and IISI Environmental
Performance Indicators 2003 STEEL(International Iron and Steel Institute, 2004)* Factor based on 2003 international data where BOFs accounted for approximately 63 percent of world steel production and EAFs
approximately 33 percent; OHF production accounted for the remaining 4 percent but is declining.
** The emission factor for EAF steelmaking does not include emissions from iron production. The emission factors for BOF and OHF
steelmaking do include emissions from blast furnace iron production.
Note that the CO2 emission factor for EAF steelmaking in this table is based on production of steel from scrap metal, and therefore theEAF emission factor does not account for any CO2 emissions from blast furnace iron making. The Tier 1 CO2 emission factor for EAFs inthis table is therefore not applicable to EAFs that use pig iron as a raw material.

2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Volume 3: Industrial Processes and Product Use

The emission factor for pellet production is based on the IPPC I&S BAT Document which provides an emission
factor range of 15.6 to 31.8 kg CO2 per tonne product. However, the CO2 emission factor for a specific process
will depend on the characteristic of the raw materials and fuels used in the process. The emission factor would
vary depending upon whether coal, natural gas, or coke oven gas was used as the primary fuel. The ‘default’emission factor provided is at the high end of the range, 30 kg CO2 per tonne product, and should be used if theinventory compiler does not know anything about the fuels or raw materials used. If the inventory compiler
knows the inputs used, CO2 emissions should be calculated using the Tier 2 method, accounting for the fuelconsumption, heating value and carbon content of the fuel.
For the purposes of Tier 1 emission calculations, it is assumed that the default fuel for production of Direct
Reduced Iron is natural gas. Natural gas-based processes account for the vast majority of installed direct reducediron (DRI) production capacity worldwide, with 63 percent of that capacity being the MIDREX process. Fuelconsumption for production of direct reduced iron using the MIDREX process is typically 10.5 - 14.5 GJ natural
gas/metric tonne solid DRI assuming 100 percent lump iron ore operation. Fuel consumption for production of
hot briquetted iron from iron fines was reported to be 12.5 GJ natural gas per tonne of product for the FINMET
process and 14 GJ natural gas per tonne of product for the CIRCORED process. The default energy consumptionof 12.5 GJ natural gas per tonne of DRI produced and the default carbon content of natural gas of 15.3 kg carbon
per GJ natural gas correspond to a CO2 emission factor of 191.3 kg carbon per tonne DRI produced (0.7 tonnes
CO2 per tonne DRI produced).

Methane emission factors
Default CH4 emission factors are provided in Table 4.2 below. The Tier 1 CH4 emission factor for cokeproduction is derived by averaging plant-specific CH4 emissions data for 11 European coke plants reported in the
IPPC I&S BAT Document. Emissions of CH4 are reported in Table 6.2 and Table 6.3 of the IPPC I&S BAT
Document in units of grams of CH4 per tonne of liquid steel produced. The CH4 emissions reported range from27 to 32 grams CH4 per tonne liquid steel. Based on the conversion factors the average CH4 emissions from the
11 European coke plants is 0.1 grams CH4 per tonne coke produced.
The Tier 1 CH4 emission factor for sinter production is derived by averaging plant-specific CH4 emissions data
for European sinter plants reported in the EMEP/CORINAIR Emissions Inventory Guidebook (EEA, 2005) andin other emission inventory reports. Emissions of CH4 are reported in Table 8.2a of the EMEP/CORINAIR
Emission Inventory Guidebook for sinter and palletising plants. For sinter plants using coke breeze an emission
factor of 50 mg CH4 per MJ was reported and a range of coke input of 38 to 55 kg coke per tonne sinter was
reported. This corresponds to an average emission factor of 0.07 kg CH4 per tonne sinter using the default valueof 28.2 TJ/Gg coke. An emission factor of 0.05 kg CH4 per tonne sinter was reported for sinter plants operatingin Finland. (Pipatti, 2001)
TABLE 4.2
TIER 1 DEFAULT CH4 EMISSION FACTORS FOR COKE PRODUCTION AND IRON & STEEL PRODUCTION
Process

Emission Factor

SourceCoke Production

0.1 g per tonne ofcoke produced

Coke Production: European IPPC Bureau (2001), Integrated Pollution
Prevention and Control (IPPC) Best Available Techniques Reference
Document on the Production of Iron and Steel, December 2001, Table
6.2-3, Page 122. http://eippcb.jrc.es/pages/FActivities.htm

Sinter Production

0.07 kg per tonne of EMEP/CORINAIR Emission Inventory Guidebook (EEA, 2005).
sinter produced
Processes With Contact: Sinter and Pelletizing Plants: Sinter andPelletizing Plants (Except Combustion 030301) Table 8.2a Emission
factors for gaseous compounds

DRI Production

1 kg /TJ (on a net
calorific basis)

Energy Volume default emission factor for CH4 Emissions fromnatural gas combustion. [See Table 2.3 of Volume 2, Chapter 2.]

TIER 2 METHOD
The default carbon contents in Table 4.3 should be used if an inventory compiler does not have information on
conditions in iron and steel-making facilities and coke production facilities, but has detailed activity data for theprocess materials and offsite transfers. The Tier 2 method, as described in Equation 4.2 for integrated cokeproduction, Equations 4.9 to 4.11 for iron and steel production and Equation 4.3 for non-integrated cokeproduction includes the major material flows in iron and steel-making and coke production that lead toemissions. Carbon contents in Table 4.3 are based on those provided in Table 1.2 and 1.3 in Volume 2, Chapter
1.

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Chapter 4: Metal Industry Emissions

TABLE 4.3
TIER 2 MATERIAL-SPECIFIC CARBON CONTENTS FOR IRON & STEEL AND COKE PRODUCTION (kg C/kg )Process Materials

Carbon Content

Blast Furnace Gas

0.17

Charcoal*

0.91

1

0.67

Coal Tar

0.62

Coke

0.83

Coke Oven Gas

0.47

Coking Coal

0.73

Direct Reduced Iron (DRI)

0.02

Dolomite

0.13

Coal

2

EAF Carbon Electrodes
3

EAF Charge Carbon

0.82
0.83

4

0.86

Gas Coke

0.83

Hot Briquetted Iron

0.02

Limestone

0.12

Natural Gas

0.73

Oxygen Steel Furnace Gas

0.35

Petroleum Coke

0.87

Purchased Pig Iron

0.04

Scrap Iron

0.04

Steel

0.01

Fuel Oil

Source: Default values are consistent with the those provided in Vol 2 and have been calculated with the assumptions below. Complete
references for carbon content data are included in Table 1.2 and 1.3 in Volume 2, Chapter 1.
Notes:
1

Assumed other bituminous coal

2

Assumed 80 percent petroleum coke and 20 percent coal tar

3

Assumed coke oven coke

4

Assumed gas/diesel fuel* The amount of CO2 emissions from charcoal can be calculated by using this carbon content value, but it should be reported as zero innational greenhouse gas inventories. (See Section 1.2 of Volume 1.)

TIER 3 METHODSThe Tier 3 method is based on aggregated plant-specific emission estimates or the application of the Tier 2equations at a plant specific level. The inventory compiler should ensure that each facility has documented theemission factors and carbon contents used, and that these emission factors are indicative of the processes andmaterials used at the facility. The Tier 3 method requires carbon contents and production/consumption mass
rates for all of the process materials and off-site transfers such as those listed in Table 4.3. While Table 4.3
provides default carbon contents, it is good practice under Tier 3 to adjust these values to reflect variations at theplant level from default values represented in the table. The default factors listed in Table 4.3 are only
appropriate for the Tier 3 method if plant-specific information indicates that they correspond to actual
conditions. It is anticipated that for the Tier 3 method the plant-specific data would include both carbon content
data and production/consumption mass rate data, and that therefore the default values in Table 4.3 would not beapplied to the Tier 3 method in most instances.

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4.2.2.4

C HOICE OF ACTIVITY DATATIER 1 METHODThe Tier 1 method requires only the amount of steel produced in the country by process type, the total amount of
pig iron produced that is not processed into steel, and the total amount of coke, direct reduced iron, pellets, andsinter produced; in this case the total amount of coke produced is assume to be produced in integrated cokeproduction facilities. These data may be available from governmental agencies responsible for manufacturing
statistics, business or industry trade associations, or individual iron and steel companies. If a country only hasaggregate data available, a weighted factor should be used. Total crude steel production is defined as the total
output of usable ingots, continuously-cast semi-finished products, and liquid steel for castings.

TIER 2 METHODThe Tier 2 method requires the total amount of iron and steel, coke oven gas, blast furnace gas, and processmaterials such as limestone used for iron and steel production, direct reduced iron production, and sinterproduction in the country, in addition to onsite and offsite production of coke. These data may be available fromgovernmental agencies responsible for manufacturing or energy statistics, business or industry trade associations,or individual iron and steel companies. These amounts can then be multiplied by the appropriate default carbon
contents in Table 4.3 and summed to determine total CO2 emission from the sector. However, activity datacollected at the plant-level is preferred (Tier 3). If this is not a key category and data for total industry-wide
reducing agents and process materials are not available, emissions can be estimated using the Tier 1 approach.

TIER 3 METHODThe Tier 3 method requires collection, compilation, and aggregation of facility-specific measured emissions data
or facility-specific process material production/consumption mass data and carbon content data The Tier 3
method can be based on a plant-specific mass balance approach (for CO2 emissions) or on plant-specific directemissions monitoring data (for both CO2 and CH4 emissions) . The Tier 3 method also may require activity data
to be collected at the plant level and aggregated for the sectors. The plant-specific data should preferably beaggregated from data furnished by individual iron and steel and coke production companies. The amounts ofprocess materials are more accurately determined in this manner. These data may also be available fromgovernmental agencies responsible for manufacturing or energy statistics, or from business or industry tradeassociations. The appropriate amounts can then be multiplied by facility specific carbon content data andsummed to determine total CO2 emissions from the sectors, and the total emissions will be more accurate thanwhen using the Tier 2 method. This approach also allows for additional accuracy by allowing individualcompanies to provide more accurate plant-specific data and/or to use more relevant carbon contents that may
differ from the default factors used in Tier 2 method.

4.2.2.5

C OMPLETENESSRELATIONSHIP TO THE ENERGY SECTOR
In estimating emissions from this source category: coke production (Energy) and iron and steel production(IPPU), there is a risk of double counting or omission in either the Industrial Processes or the Energy Sector.
Since the primary use of carbon sources (predominantly coke, but also coal, oil, natural gas, limestone, etc.) is to
produce pig iron, the CO2 and CH4 emissions from iron and steel production including sinter production are
considered industrial process emissions and should be reported as such. The CO2 and CH4 emissions from cokeproduction (both fuel consumption and conversion losses) are categorised as energy production and should bereported as such. However, for integrated production and iron and steel with onsite coke production, there may
be flows of by-products (e.g., coke oven gas, blast furnace gas, coke oven by-products) between the cokeproduction facility and the iron and steel production facility, creating potential double counting issues. Carbon
consumed in the from of coke oven gas at an iron and steelmaking facility and the resulting CO2 and CH4
emissions would be categorized as IPPU emissions and reported as such. Carbon consumed in the form of blast
furnace gas at an onsite coke production facility and the resulting CO2 and CH4 emissions would be categorized
as Energy emissions and should reported as such Tracking of such carbon flows will require good knowledge ofthe inventory in that source category.
Because of the dominant role of coke, it is important to consider the existence of coke making at a facility anddefine the boundary limits of a carbon balance at an iron and steelmaking facility to assure that CO2 emissions
are not double-counted. CO2 and CH4 emissions associated with onsite and offsite coke making are to bereported under Energy Sector (see Volume 2).

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Chapter 4: Metal Industry Emissions

OTHER FORMS OF CARBON
Although the dominant means of producing crude iron, or pig iron, is the blast furnace using coke, other forms ofcarbon (e.g., pulverized coal, coal derivatives, recycled plastics or tires, natural gas, or fuel oil) can also be used
to substitute for some portion of the coke in the blast furnace. In these cases, these materials should be accounted
for as process sources of carbon in the same manner as coke, and care should be taken to deduct these materials
from any general energy statistics if they are included there. Iron can also be produced in other types of ironmaking vessels besides blast furnaces, often using natural gas or coal instead of coke, and these carbon sources
should be accounted for in the same manner as coke because they are serving the same purpose.
In most blast furnaces, the iron making process is aided by the use of carbonate fluxes (limestone or dolomite).
Because these materials are necessary raw materials for the process, they should be accounted for as part of theiron and steelmaking inventory. Again, however, care should be taken not to double-count emissions associatedwith limestone and dolomite usage if accounted for separately in the minerals sector. (See Section 2.5, Other
Process Uses of Carbonates, in this volume.)

SINTER
Some integrated facilities also utilize sinter plants to convert iron-bearing fines into an agglomerate (or sinter)suitable for use as a raw material in the blast furnace. Typically, coke fines (or coke breeze) are used as a fuel inthe sintering process and are a source of CO2 and CH4 emissions. If the coke fines are produced at a coke plantwithin the facility and the CO2 and CH4 emissions are accounted for in the coal entering the facility, or if thecoke breeze is otherwise accounted for as purchased coke, the CO2 and CH4 emissions from coke used insintering should not be double-counted. Emissions from sinter production are categorised as IPPU emissions
and should be reported as such.

EXHAUST GASESIt is important not to double count the use of blast-furnace-derived by-product gases such as blast furnace gas, or
recovered BOF off-gas as energy in the energy sector as sources of CO2, if they have been accounted for as
process emissions. Process emissions should include all carbon inputs in the blast furnace, used as the primary
reductant. In a typical fully integrated coke and iron and steel plant situation, adjustments may need to be madefor coke oven by-products and the carbon content of shipped steel, which should be clearly mentioned in thedescription of the sources. In some cases, it may also be necessary to make adjustments for blast furnace gas, oriron that may be sold or transferred offsite. The process flow of exhaust gases are clearly illustrated in Figures
4.1-4.5.

ELECTRODE CONSUMPTIONElectrode consumption amounts to about 3.5 kg/tonne for EAF furnaces. However, depending upon thecharacteristics of the charged materials, some carbon may be added to the EAF (typically about 20 kg/tonne) forprocess control purposes or may be contained in the charged materials themselves as iron substitutes, anincreasingly more frequent trend. In these cases, CO2 and CH4 emissions from these additional carbon-bearing
materials should be considered process-related and accounted for in the inventory because their carbon content is
not as likely to have been accounted for elsewhere in the inventory. In addition, if natural gas is used to enhancereactions in an EAF as reducing agent it should be accounted for as a carbon source as all process materials usedin iron and steel manufacturing are reported as IPPU emissions.
Some specialty steel production takes place in electric induction furnaces, in which case the charge is 100
percent steel scrap and where there are no carbon electrodes. There are no appreciable CO2 or CH4 emissions
from this steelmaking process.

OHF PROCESS
Although the OHF is no longer prevalent, it may be necessary to inventory CO2 and CH4 emissions from thissteelmaking process in some countries. An open hearth furnace is typically charged with both molten iron andscrap as in the case of a BOF, and oxygen is injected into the furnace, but reduction of carbon in the iron andmelting of the charge also takes place by firing fossil fuels (e.g., natural gas, fuel oil, coal or tar) across thesurface of the raw material bath. Carbon in the iron may be ignored, as in the case of the BOF, because it has
been accounted for as a source of carbon for iron-making. However, carbon in the fuels used in the open hearth
process should be accounted for as IPPU emissions.

4.2.2.6

D EVELOPING A CONSISTENT TIME SERIESEmissions from coke production, sinter production, and iron and steel and production should be calculated using
the same method for every year in the time series. Where data are unavailable to support a more rigorous method

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Volume 3: Industrial Processes and Product Use

for all years in the time series, these gaps should be recalculated according to the guidance provided in Volume 1,
Chapter 5, Time Series Consistency and Recalculation.

4.2.3

Uncertainty assessment

The default emission factors for coke production and iron and steel production used in Tier 1 may have an
uncertainty of ± 25 percent. Tier 2 material-specific carbon contents would be expected to have an uncertainty
of 10 percent. Tier 3 emission factors would be expected to be within 5 percent if plant-specific carbon content
and mass rate data are available. Table 4.4 provides an overview of the uncertainties for emission factors, carbon
contents and activity data.
TABLE 4.4
UNCERTAINTY RANGES
MethodData Source

Uncertainty Range

Tier 1

Default Emission Factors
National Production Data

± 25%
± 10%

Tier 2

Material-Specific Default Carbon Contents
National Reducing Agent & Process Materials Data

± 10%
± 10%

Tier 3Company-Derived = Process Materials Data
Company-Specific Measured CO2 and CH4 Data
Company-Specific Emission Factors

± 5%
± 5%
± 5%

For Tier 1 the most important type of activity data is the amount of steel produced using each method. National
statistics should be available and likely have an uncertainty of ± 10 percent. For Tier 2, the total amount of
reducing agents and process materials used for iron and steel production would likely be within 10 percent. Tier
3 requires plant-specific information on the amounts of reducing agents and process materials (about 5 percent
uncertainty). Also actual emissions data for Tier 3 would be expected to have ± 5 percent uncertainty. Tier 3
uncertainty may be more accurately derived based on an analysis of the actual data received.

4.2.4
4.2.4.1

Quality Assurance/Quality Control (QA/QC),
Reporting and Documentation
Q UALITY A SSURANCE /Q UALITY C ONTROL (QA/QC)

It is good practice to conduct quality control checks as outlined in Volume 1, Chapter 6, and an expert review ofthe emissions estimates. Additional quality control checks as outlined in Volume 1, Chapter 6, and quality
assurance procedures may also be applicable, particularly if higher tier methods are used to determine emissions
from this source category. Inventories agencies are encouraged to use higher tier QA/QC for key categories as
identified in Volume 1, Chapter 4.
In addition to the guidance in Volume 1, specific procedures of relevance to this source category are outlined
below.

Review of emission factors and carbon contents
Inventory compilers should compare aggregated national emission factors and carbon contents with the IPCC
default factors carbon contents in order to determine if the national value is reasonable relative to the IPCC
default. Differences between national default values should be explained and documented, particularly if they are
representative of different circumstances.

Site-specific activity data check
For site-specific data, inventory compilers should review inconsistencies between sites to establish whether theyreflect errors, different measurement techniques, or result from real differences in emissions, operational
conditions or technology.
Inventory compilers should ensure that emission factors and activity data are developed in accordance withinternationally recognised and proven measurement methods. If the measurement practices fail this criterion,

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Chapter 4: Metal Industry Emissions

then the use of these emissions or activity data should be carefully evaluated, uncertainty estimates reconsideredand qualifications documented. If there is a high standard of measurement and QA/QC is in place at most sites,
then the uncertainty of the emissions estimates may be revised downwards.

Expert review
Inventory compilers should include key industrial trade organisations associated with iron and steel production
in a review process. This process should begin early in the inventory development process to provide input to thedevelopment and review of methods and data acquisition
Third party reviews are also useful for this source category, particularly related to initial data collection,measurement work, transcription, calculation and documentation.

Activity data check
For all tier levels, inventory compilers should check with Volume 2, Chapter 2 (Stationary Combustion ofEnergy Sector) to ensure that emissions from reducing agents and process materials (coal, coke, natural gas, etc.)
are not double-counted or omitted.
Inventory compilers should examine any inconsistency between data from different plants to establish whether
these reflect errors, different measurement techniques or result from real differences in emissions, operational
conditions or technology. This is particularly relevant to the plant-specific estimates of amounts of reducing
agents or reported carbon content of process materials.
Inventory compilers should compare aggregated plant-level estimates to industry totals for process materials
consumption where such trade data are available.

4.2.4.2

R EPORTING AND D OCUMENTATION

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Volume 1, Section 6.11. It is not practical to include all documentation in the national
inventory report. However, the inventory should include summaries of methods used and references to source
data such that the reported emissions estimates are transparent and steps in their calculation may be retraced.

TIER 1 METHOD
Besides reporting of estimated emissions, it is good practice to report the total steel production by process andcorresponding emission factors used and to report the amount of iron produced that is not processed into steel. In
the corresponding table, it should be noted that reported emissions are only part of total emissions from thesector and that coke production emissions are categorized as energy emissions and are reported in Volume 2,
Chapter 2, Stationary Combustion of Energy Sector.

TIER 2 METHODSGood practice is to document the estimated or calculated emissions, all activity data, and corresponding
emission factors and any assumptions or data justifying alternative emission factors. There should be a clear
explanation of the linkage with the source category 1A (Fuel Combustion) estimate for integrated cokeproduction emissions to demonstrate that double counting or missing emissions have not occurred.

TIER 3 METHODGood practice is to document the calculated emissions and source of all data, taking into account the need toprotect the confidentiality of data for specific facilities if the data are business-sensitive or of a proprietary nature.
In addition, inventory compilers should for all tiers, document all information needed to reproduce the estimate,
as well as the QA/QC procedures.

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4.3

FERROALLOY PRODUCTION

4.3.1

Introduction

Ferroalloy is the term used to describe concentrated alloys of iron and one or more metals such as silicon,
manganese, chromium, molybdenum, vanadium and tungsten. Silicon metal production is usually included in the
ferroalloy group because silicon metal production process is quite similar to the ferrosilicon process. These
alloys are used for deoxidising and altering the material properties of steel. Ferroalloy facilities manufacture
concentrated compounds that are delivered to steel production plants to be incorporated in alloy steels. Silicon
metal is used in aluminium alloys, for production of silicones and in electronics. Ferroalloy production involves
a metallurgical reduction process that results in significant carbon dioxide emissions.
In ferroalloy production, raw ore, carbon materials and slag forming materials are mixed and heated to hightemperatures for reduction and smelting. The carbonaceous reductants are usually coal and coke, but bio-carbon(charcoal and wood) is also commonly used as a primary or secondary carbon source. Carbon dioxide (CO2) andmethane (CH4) emissions from coke production are estimated in Section 4.2 and reported within the Energy
Sector. Electric submerged arc furnaces with graphite electrodes or consumable Søderberg electrodes are used.
The heat is produced by the electric arcs and by the resistance in the charge materials. The furnaces may be open,
semi-covered or covered. A commonly used technology is the submerged-arc open-top electric furnace (EAF).
In the EAF, passing current through graphite electrodes suspended in a cup-shaped, refractory-lined steel shellaccomplishes heating. Carbon reduction of the metallic oxides occurs as both coke and graphite electrodes are
consumed. The carbon in the electrodes captures the oxygen from the metal oxides to form CO, while the ores
are reduced to molten base metals. The component metals then combine in the solution.
In addition to emissions originating from reducing agents and electrodes, the calcination of carbonate fluxes suchas limestone or dolomite, when used, contribute to the emission of greenhouse gases.
Primary emissions in covered arc furnaces consist almost entirely of CO as opposed to CO2, due to the strong
reducing environment. This CO is either utilised for energy production in boilers, or it is flared. The energy
produced is assumed to be used internally at the site and the carbon content of the CO subsequently converted to
CO2 in-plant.
The CO gas produced in open or semi-closed furnaces is burnt to CO2 above the charge level. Any CO emitted tothe atmosphere is assumed to be converted to CO2 within days afterwards. While CO2 is the main greenhousegas from ferroalloy production, recent research has shown that CH4, and N2O account for an equivalentgreenhouse emission of up to 5 percent of the CO2 emissions from ferrosilicon (FeSi) and silicon-metal (Si-metal)
production. Methodologies are presented for CO2 and CH4 emissions in this section. These emissions should bebetter investigated for all ferroalloy production, and more measurements of these emissions should be done from
FeSi and Si-metal production.

4.3.2

Methodological issues

4.3.2.1

C HOICE OF METHODMETHODOLOGY FOR CO 2
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-specificconsumption data, but alternatively from industry-wide data using emission factors similar to those used toestimate 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 inEquation 4.15.

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Chapter 4: Metal Industry Emissions

EQUATION 4.15
CO2 EMISSIONS FOR FERROALLOY PRODUCTION BY THE TIER 1 METHOD
E CO 2 = ∑ (MPi • EFi )i

Where:
ECO2 = CO2 emissions, tonnes
MPi = production of ferroalloy type i, tonnes
EFi = generic emission factor for ferroalloy type i, tonnes CO2/tonne specific ferroalloy productTier 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∑ means the sum of all i, h, j, k or l

EQUATION 4.16
CO2 EMISSIONS FOR FERROALLOY PRODUCTION BY TIER 2 METHOD()

ECO 2 = ∑ M reducing agent , i • EFreducing agent , i + ∑ (M ore, h • CContent ore, h ) •
i

h

(

44
12

44
) 12

+ ∑ M slag forming material , j • CContent slag forming material , j •
j

(

44
) 12

− ∑ M product , k • CContent product , k •
k

(

44
) 12

− ∑ M non − product outgoing stream, l • CContent non − product outgoing stream, l •lWhere:
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 material, 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 productMnon-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.

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 amountsof carbon in carbonate ores and slag forming materials will vary. The most accurate method is therefore to2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Volume 3: Industrial Processes and Product Use

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
44
ECO 2 = ∑ M reducing agent , i • CContent reducing agent , i •12i44+ ∑ (M ore, h • CContentore, h ) •12h44+ ∑ M slag forming material , j • CContent slag forming material , j •
12
j

(

)

(

)

(

44
) 12

− ∑ M product , k • CContent product , k •
k

(

44
) 12

− ∑ M non − product outgoing stream, l • CContent non − product outgoing stream, l •lWhere:
ECO2 = CO2 emissions frm ferroalloy production, tonnes
Mreducing agent, i = mass of reducing agent i, tonnes
CContentreducing agent, i = 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 material, 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 productMnon-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.

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Chapter 4: Metal Industry Emissions

Figure 4.9

Decision tree for estimation of CO 2 emissions from ferroalloy production
Start

Are all data
relating to the reducing
agent and output streams
available?

Yes

Calculate emissions
using plant specific data.
Box 3: Tier 3

No

Are national
data available by processmaterials?

Yes

Calculate emissions
using reducing agent
specific emission factors.
Box 2: Tier 2

No

Is this a key
category1?

No

Calculate emissions
using default emission
factors and national
production data.
Box 1: Tier 1

Yes
Collect data for the Tier 3or the Tier 2 method.
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 CH 4 AND DISCUSSION OF N 2 O EMISSIONSThe 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 tobatch-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 verylarge and thus, a methodology is not provided.

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Figure 4.10

Decision tree for estimation of CH 4 emissions from FeSi and Si alloy
production
Start

Are emissions
data available on afacility level?

Yes

Aggregate facilityspecific measured
emissions data as basis
for the Tier 3 method.
Box 3: Tier 3

No

Are countryspecific FeSi and Si alloy
process operations
known ?

Yes

Calculate emissions
using operation-specificemission factors.
Box 2: Tier 2

No

Is this a key
category1?

No

Multiply data by
default emission factors.
Box 1: Tier 1

Yes
Collect data for the Tier 3or the Tier 2 method.
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 METHODE CH 4 = ∑ (MPi • EFi )i

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 product4.36

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Chapter 4: Metal Industry Emissions

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.

4.3.2.2

C HOICE OF EMISSION FACTORSEMISSION FACTORS FOR CO 2
Tier 1 method: production-based emission factors
When the only data available are national ferroalloy production statistics, it is good practice to use default
emission factors. However, because of widely disparate factors depending on the type of ferroalloy production, it
is necessary to determine how much tonnage is produced by which method and then to sum the product of thefactors shown in Table 4.5 and the appropriate production tonnages. These factors are based on expert judgement
using typical practice for the ferroalloy production scenarios listed. If any bio-carbon, except some woodchips
for FeSi and Si-metal production, is used, the factors cannot be employed.

TABLE 4.5
GENERIC CO2 EMISSION FACTORS FOR FERROALLOY PRODUCTION(tonnes CO2/tonne product)
Type of Ferroalloy

Emission Factor

Ferrosilicon 45% Si

2.5Ferrosilicon 65 % Si

3.6

Ferrosillicon 75% Si

4.0

Ferrosillicon 90% Si

4.8

Ferromanganeses (7% C)

1.3

Ferromanganeses (1% C)

1.5

Silicomanganese

1.4

Silicon metal

5.0

Ferrochromium

1.3 (1.6 with sinter plant)

Source: IPCC (1997), IPCC (2000), Olsen (2004) and Lindstad (2004)

These default emission factors have been assessed by Olsen (2004) for the manganese alloys, Lindstad (2004)
for the silicon alloys and by Olsen, Monsen and Lindstad (1998) for FeCr.
For FeMn alloys the emission factors are based on production where the Mn containing raw materials are a
mixture of oxide ores, carbonate ores and imported Mn-sinter. If the sinter is produced abroad it will not giveany contribution to the national greenhouse gas inventory. Emission from sinter production must be reported
where the production is located.
The factor for FeSi90 and Si-metal is based on a Fix C consumption of 110 percent of the stoichiometric amountneeded for reduction of SiO2. For the other FeSi-alloys the factor is based on 114 percent of the stoichiometricamount of Fix C.

Tier 2 method: production-based, raw material specific emission factors
The emission factors for the reducing agents used in production of manganese and silicon alloys are given in
Table 4.6. The factors have been assessed by Olsen (2004) for use in manganese alloys production and by
Lindstad (2004) for use in silicon alloys.

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TABLE 4.6
CO2 EMISSION FACTORS FOR FERROALLOY PRODUCTION(tonnes CO2/tonne reducing agent)
Reducing agent (usage)

Emission Factor

Coal (for FeSi and Si-metal)

3.1

Coal (for other ferroalloys)* (See below)

Coke (for FeMn and SiMn)

3.2-3.3

Coke (for Si and FeSi)

3.3-3.4

Coke (for other ferroalloys)* (See below)

Prebaked electrodes

3.54

Electrode paste

3.4

Petroleum coke

3.5*: Inventory compilers are encouraged to use producer-specific values based on average blend of coal and/or coke for each ferroalloy
producer.
Source: Olsen (2004), Lindstad (2004)

Tier 3 method: calculations based on amounts and analyses of reducing agents
For the Tier 3 method, it is necessary to determine the carbon contents of the reducing agents used in the
production processes. But most ferroalloys producers analyse only on the basis of percentage of ash and volatiles,
and calculate:
Fix C % = 100 % – % Ash – % Volatiles.
In that case, the total C-contents of reducing agents. is calculated by the following equation.
EQUATION 4.19
CARBON CONTENTS OF FERROALLOY REDUCTING AGENTS
CContent reducing agent ,i = FFixC ,i + Fvolatiles ,i • C v

Where:
CContentreducing agent, i = carbon content in reducing agent i, tonnes C/tonne reducing agent
FFixC,i = mass fraction of Fix C in reducing agent i, tonnes C/ tonne reducing agent
Fvolatiles,i = mass fraction of volatiles in reducing agent i, tonnes volatiles/ tonne reducing agent
Cv = carbon content in volatiles, tonnes C/tonne volatiles(Unless other information is available, Cv = 0.65 is used for coal and 0.80 for coke.)

EMISSION FACTORS FOR CH 4
Tier 1 method: FeSi and Si alloy production-based emission factors
When the only data available are national ferroalloy production statistics, it is good practice to use default
emission factors. However, because of the disparate factors depending on the type of ferroalloy production, it isnecessary to determine how much tonnage is produced by which method and then to sum the product of thefactors shown in Table 4.7 and the appropriate production tonnages. The default emission factors for CH4 isbased on the averages of a small number of operation-specific measurements (shown in Table 4.7 for Tier 2)
carried out by SINTEF and DNV mainly in 1995 and 1998 (FFF (2000)).

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Chapter 4: Metal Industry Emissions

TABLE 4.7
DEFAULT EMISSION FACTORS FOR CH4 (kg CH4/tonne product)
Emission

Alloy

Emission Factor

CH4

Si-metal

1.2

FeSi 90

1.1

FeSi 75

1.0

FeSi 65

1.0

Source: FFF (2000)

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 factors are operation
specific. The procedure is otherwise the same as that outlined in Equation 4.18, using values in Table 4.8.
TABLE 4.8
EMISSION FACTORS FOR CH4 (kg CH4/tonne product)
Emission

Alloy

Operation of Furnace
Batch-charging

CH4

Sprinkle-charging 1)

Sprinkle-charging and>7500C 2)

Si-metal

1.5

1.2

0.7

FeSi 90

1.4

1.1

0.6

FeSi 75

1.3

1.0

0.5

FeSi 65

1.3

1.0

0.5

1

Sprinkle-charging is charging intermittently every minute.

2

Temperature in off-gas channel measured where the thermocouple cannot ‘see’ the combustion in the furnace hood.

Tier 3 method: Direct measurements
Tier 3 is based on measurements rather than emission factors. The inventory compiler should consult guidanceon plant-level measurements outlined in Volume 1, Chapter 2, and on QA/QC of measurements in Volume 1,
Chapter 6.

4.3.2.3

C HOICE OF ACTIVITY DATATIER 1 METHODThe Tier 1 method requires only the amount of ferroalloy produced in the country by product type. These data
may be available from governmental agencies responsible for manufacturing statistics, business or industry tradeassociations, or individual ferroalloy companies. These tonnages can then be multiplied by the corresponding
emission factors in Table 4.5 to estimate CO2 emissions from the sector and Table 4.7 to estimate CH4 emissions
from the sector.

TIER 2 METHODThe Tier 2 method requires the total amount of reducing agent and other process materials used for ferroalloy
production in the country, and knowledge of processes used. These data may be available from governmental
agencies responsible for manufacturing or energy statistics, business or industry trade associations, or individual
ferroalloy companies. These amounts can then be multiplied by the appropriate generic emission factors in
Tables 4.6 and 4.8 and summed to determine total CO2 and CH4 emissions from the sector. However, activity
data collected at the plant-level is preferred.

TIER 3 METHODThe Tier 3 method requires collection, compilation, and aggregation of facility-specific emissions data. These
data may be available directly from companies.

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4.3.2.4

C OMPLETENESS

In estimating emissions from this source category, there is a risk of double-counting or omission in either the
Industrial Processes or the Energy Sector. Since the primary use of carbon sources (coal, coke, limestone,
dolomite etc.) is to produce ferroalloys, the emissions are considered to be industrial process emissions andshould be reported as such. It should be noted that the risk of double counting is particularly high for the Tier 1
approach. Any deviation from reporting emissions as originating from an industrial process should be explicitly
mentioned in the inventory, and a double-counting/completeness check should be performed.

4.3.2.5

D EVELOPING A CONSISTENT TIME SERIESEmissions from ferroalloy production should be calculated using the same method for every year in the timeseries. Where data are unavailable to support a Tier 3 method for all years in the time series, these gaps should
be recalculated according to the guidance provided in Volume 1, Chapter 5.

4.3.3

Uncertainty assessment

Uncertainties for ferroalloy production result predominantly from uncertainties associated with activity data, andto a lesser extent from uncertainty related to the emission factor. Although some ferroalloys may be produced
using wood or other biomass as a carbon source, information and data regarding these practices were notavailable. Emissions from ferroalloys produced with wood or other biomass would not be counted under thissource because wood-based carbon is of biogenic origin. Emissions from ferroalloys produced with coking coalor graphite inputs would be counted in national trends, but may generate differing amounts of CO2 per unit offerroalloy produced compared to the use of petroleum coke.

4.3.3.1

E MISSION FACTOR UNCERTAINTIESFor Tier 3, actual emissions data would be expected to have less than 5 percent uncertainty. For Tier 2, thematerial-specific emission factors would be expected to be within 10 percent, which would provide lessuncertainty overall than for Tier 1. Emission factors would be expected to be within 10 percent or less than 5
percent if plant-specific carbon content data are available. The default emission factors used in Tier 1 may havean uncertainty of 25 to 50 percent.

4.3.3.2

A CTIVITY DATA UNCERTAINTIESFor Tier 1 the most important type of activity data is the amount of ferroalloy production by product type.
National statistics should be available and likely have an uncertainty less than 5 percent. Tier 2 applied withplant-specific information on the amounts of reducing agents and process materials as applied in Tier 2 methodshould not exceed 5 percent uncertainty.
TABLE 4.9
UNCERTAINTY RANGES
MethodData Source

Tier 1

National Production Data
Default Emission Factors< 5%< 25 %

Tier 2Company-Derived Reducing Agent & Process Materials
National Reducing Agent & Process Materials Data
Company-Specific Emission Factors
Material-Specific Default Emission Factors

< 5%
< 5%
< 5%
< 10%

Tier 3Company-Specific Measured CO2 Data

< 5%

4.40

Unertainty Range

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Chapter 4: Metal Industry Emissions

4.3.4
4.3.4.1

Quality Assurance/Quality Control (QA/QC),
Reporting and Documentation
Q UALITY A SSURANCE /Q UALITY C ONTROL (QA/QC)

It is good practice to conduct quality control checks as outlined in Volume 1, Chapter 6, and an expert review ofthe emissions estimates. Additional quality control checks as outlined in Volume 1, Chapter 6, and quality
assurance procedures may also be applicable, particularly if higher tier methods are used to determine emissions
from this source category. Inventories agencies are encouraged to use higher tier QA/QC for key categories as
identified in Volume 1, Chapter 4.
In addition to the guidance in Volume 1, specific procedures of relevance to this source category are outlined
below.

Review of emission factors
Inventory compilers should compare aggregated national emission factors with the IPCC default factors in orderto determine if the national factor is reasonable relative to the IPCC default. Differences between national factors
and default factors should be explained and documented, particularly if they are representative of different
circumstances.

Site-specific activity data check
For site-specific data, inventory compilers should review inconsistencies between sites to establish whether theyreflect errors, different measurement techniques, or result from real differences in emissions, operational
conditions or technology. For ferroalloy production, inventory compilers should compare plant data with otherplants.
Inventory compilers should ensure that emission factors and activity data are developed in accordance withinternationally recognised and proven measurement methods. If the measurement practices fail this criterion,
then the use of these emissions or activity data should be carefully evaluated, uncertainty estimates reconsideredand qualifications documented. If there is a high standard of measurement and QA/QC is in place at most sites,
then the uncertainty of the emissions estimates may be revised downwards.

Expert review
Inventory compilers should include key industrial trade organisations associated with ferroalloy production in areview process. This process should begin early in the inventory development process to provide input to thedevelopment and review of methods and data acquisition
Third party reviews are also useful for this source category, particularly related to initial data collection,measurement work, transcription, calculation and documentation.

Activity data check
For all tier levels, inventory compilers should check with Volume 2, Chapter 2, Stationary Combustion ofEnergy Sector, to ensure that emissions from reducing agents and process materials (coal, coke, natural gas, etc.)
are not double-counted or omitted.
Inventory compilers should examine any inconsistency between data from different plants to establish whether
these reflect errors, different measurement techniques or result from real differences in emissions, operational
conditions or technology. This is particularly relevant to the plant-specific estimates of amounts of reducing
agents or reported carbon content of process materials.
Inventory compilers should compare aggregated plant-level estimates to industry totals for process materials
consumption where such trade data are available.

4.3.4.2

R EPORTING AND D OCUMENTATION

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Volume 1, Section 6.11. It is not practical to include all documentation in the national
inventory report. However, the inventory should include summaries of methods used and references to source
data such that the reported emissions estimates are transparent and steps in their calculation may be retraced.

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TIER 1 METHOD
Besides reporting of estimated emissions, it is good practice to report the total ferroalloy production by process
and corresponding emission factors used. In the corresponding table, it should be noted that reported emissions
are only part of total emissions from the sector and the rest are reported elsewhere Volume 2, Chapter 2,
Stationary Combustion of Energy Sector.

TIER 2 METHODSGood practice is to document the estimated or calculated emissions, all activity data, and corresponding
emission factors and any assumptions or data justifying alternative emission factors. There should be a clear
explanation of the linkage with the Fuel Combustion Sub-Sector estimate to demonstrate that double counting or
missing emissions have not occurred.

TIER 3 METHODGood practice is to document the calculated emissions and source of all data, taking into account the need toprotect the confidentiality of data for specific facilities if the data are business-sensitive or of a proprietary nature.
In addition, inventory compilers should for all tiers, document all information needed to reproduce the estimate,
as well as the QA/QC procedures.

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Chapter 4: Metal Industry Emissions

4.4

PRIMARY ALUMINIUM PRODUCTION

4.4.1

Introduction

This section covers process emissions from primary aluminium production2. Worldwide, primary aluminium is
produced exclusively by the Hall-Heroult electrolytic process. In this process, electrolytic reduction cells differ
in the form and configuration of the carbon anode and alumina feed system and belong to one of four technology
types: Centre-Worked Prebake (CWPB)3, Side-Worked Prebake (SWPB), Horizontal Stud Søderberg (HSS) andVertical Stud Søderberg (VSS).
The most significant process emissions are:(i) Carbon dioxide (CO2) emissions from the consumption of carbon anodes in the reaction to convert
aluminium oxide to aluminium metal;(ii) Perfluorocarbons (PFCs) emissions of CF4 and C2F6 during anode effects.
Also emitted are smaller amounts of process emissions, CO, SO2, and NMVOC. SF6 is not emitted during theelectrolytic process and is only rarely used in the aluminium manufacturing process, where small quantities are
emitted when fluxing specialized high magnesium aluminium alloys4.
The decision trees in Figures 4.11 and 4.12 provide guidance for selecting a methodology estimating emissions
from aluminium production. All inventory compilers in countries with aluminium production should be able toimplement at a minimum level the Tier 1 method and thereby ensure completeness of reporting. Although thischapter presents default emission factors for both CO2 and PFC emissions, countries should make every effort touse higher Tier methods because emission rates can vary greatly, and the uncertainty associated with Tier 1
factors is very high. Aluminium smelters routinely collect the process data needed for calculation of Tier 2emissions factors.

4.4.2
4.4.2.1

Methodological issues
C HOICE OF METHOD FOR CO 2 EMISSIONS FROM PRIMARY
ALUMINIUM PRODUCTION

During normal operations, aluminium is produced at the cathode and carbon is consumed at the anode per theelectrolytic reduction reaction:

2Al2O3 + 3C Æ 4Al + 3CO2

Most carbon dioxide emissions result from the electrolysis reaction of the carbon anode with alumina (Al2O3).
The consumption of prebaked carbon anodes and Søderberg paste is the principal source of process related
carbon dioxide emissions from primary aluminium production. Other sources of process related carbon dioxide
emissions associated with Prebake anode baking account for less than 10 percent of the total non-energy related
carbon dioxide emissions.
The reactions leading to carbon dioxide emissions are well understood and the emissions are very directly
connected to the tonnes of aluminium produced through the fundamental electrochemical equations for alumina
reduction at a carbon anode and oxidation from thermal processes. Both of these fundamental processes

2

Emissions from the combustion of fossil fuels associated with primary aluminium production, bauxite mining, bauxite ore
refining, and aluminium production from recycled sources are covered in Volume 2: Energy. Also, carbon dioxide
emissions associated with production of electricity from fossil fuel combustion to produce aluminium are also covered inVolume 2.

3

Including Point Feed Prebake and Bar Broken Prebake cells.

4

A 2004 IAI survey found no evidence of SF6 being emitted from primary aluminium smelting through the Hall-Heroultelectrolytic production process.

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producing carbon dioxide are included in process parameters routinely monitored at the production facilities, thenet anode carbon consumed for Prebake facilities, or anode paste consumption for Søderberg facilities.
For the CO2 emissions calculation, production data require technology differentiation as Søderberg or
Prebake.There is no need for further differentiation as to the specific type of Søderberg or Prebake technology.
The decision tree shown in Figures 4.11 describes good practice in choosing the CO2 inventory methodology
appropriate for national circumstances.

Figure 4.11

Decision tree for calculation of CO 2 emissions from primary aluminium
production
Start

Are
data available
for anode or paste
consumption?

YesIs
facility specificanode or paste composition
available1?

Yes

Calculate CO2
emissionsusing Tier 3.
Box 3: Tier 3NoNo

Calculate CO2
emissionsusing Tier 2.
Box 2: Tier 2

Is this a key
category2?

NoAre
production data available bytechnology3?

Yes

No

Collect process data.

Estimate annual
production
by technology.

Yes

Calculate CO2
emissionsusing Tier 1.
Box 1: Tier 1

Note:
1. See International Aluminium Institute, The Aluminium Sector Greenhouse Gas Protocol, 2005.
2. 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.
3. For CO2 emissions calculation, the production data requires technology differentiation as Søderberg or Prebake. There is no need forfurther differentiation as to the specific type of Søderberg or Prebake technology.

Tier 1 method for CO 2 emissions
The Tier 1 method for calculating CO2 emissions uses only broad cell technology characterizations (Prebake or
Søderberg) as a lower order estimate of CO2 emissions from aluminium production. Given the uncertainty
associated with the Tier 1 method, it is good practice to use higher tier methods if CO2 from primary aluminium
is a key category.
Total CO2 emissions are calculated according to Equation 4.20.

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Chapter 4: Metal Industry Emissions

EQUATION 4.20
PROCESS CO2 EMISSIONS FROM ANODE AND/OR PASTE CONSUMPTION (TIER 1 METHOD)
E CO 2 = EFP • MPP + EFS • MPS

Where:
ECO2 = CO2 emissions from anode and/or paste consumption, tonnes CO2
EFP = Prebake technology specific emission factor (tonnes CO2/tonne aluminium produced)
MPP = metal production from Prebake process (tonnes Al)
EFS = Søderberg technology specific emission factor (tonnes CO2/tonne aluminium produced)
MPS = metal production from Søderberg process (tonnes Al)

Tier 2 or Tier 3 methods for CO 2 emissions
For both the Prebake and Søderberg processes CO2 emissions are calculated using a mass balance approach thatassumes that the carbon content of net anode consumption or paste consumption is ultimately emitted as CO2.
The Tier 2 methods for both Prebake and Søderberg processes make use of typical industry values for impurities
while the Tier 3 methods uses actual concentrations of impurities. The choice of method between the Tier 2 andTier 3 method will depend on whether anode or paste composition data are available at the individual plant level.

CO 2 emissions for Prebake cells (CWPB and SWPB):The CO2 emissions for the Tier 2 and the Tier 3 method for Prebake cells are calculated according to Equation
4.21. Tier 3 requires specific operating facility data for all the components in Equation 4.21, whereas Tier 2 isbased on default values for some of the components. Section 4.4.2.2 below provides more details on using theseparameters.
EQUATION 4.21
CO2 EMISSIONS FROM PREBAKED ANODE CONSUMPTION (TIER 2 AND TIER 3 METHODS)
100 − S a − Asha 44•
ECO 2 = NAC • MP •100
12Where:
ECO2 = CO2 emissions from prebaked anode consumption, tonnes CO2
MP = total metal production, tonnes Al
NAC = net prebaked anode consumption per tonne of aluminium, tonnes C/ tonne Al
Sa = sulphur content in baked anodes, wt %Asha = ash content in baked anodes, wt %44/12 = CO2 molecular mass: carbon atomic mass ratio, dimensionless
Equation 4.21 should be applied to each Prebake smelter in the country and the results summed to arrive at total
national emissions. It is possible to use a hybrid Tier 2/3 approach if data on ash or sulphur content are notavailable for each smelter.
Emissions from the combustion of fossil fuels used in the production of baked anodes are covered in Volume 2:
Energy. However, two other sources of CO2 emissions are associated with anode baking furnaces – thecombustion of volatile matter released during the baking operation and the combustion of baking furnace
packing material (coke). Equations 4.22 and 4.23 can be used for the calculation of such emissions.5

5

For additional information on the application of these equations to estimate emissions from combustion of volatile matter,see the IAI Greenhouse Gas Protocol (IAI, 2005a).

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EQUATION 4.22
CO2 EMISSIONS FROM PITCH VOLATILES COMBUSTION (TIER 2 AND TIER 3 METHODS)
44
ECO 2 = (GA − H w − BA − WT ) •12

Where:
ECO2 = CO2 emissions from pitch volatiles combustion, tonnes CO2
GA = initial weight of green anodes, tonnes
Hw = hydrogen content in green anodes, tonnes
BA = baked anode production, tonnes
WT = waste tar collected, tonnes

EQUATION 4.23
CO2 EMISSIONS FROM BAKE FURNACE PACKING MATERIAL (TIER 2 AND TIER 3 METHODS)
100 − S pc − Ash pc 44•
ECO 2 = PCC • BA •100
12Where:
ECO2 = CO2 emissions from bake furnace packing material, tonnes CO2
PCC = packing coke consumption, tonnes/tonne BA
BA = baked anode production, tonnes
Spc = sulphur content in packing coke, wt %Ashpc = ash content in packing coke, wt %CO 2 emissions for Søderberg cells (VSS and HSS):The CO2 emissions for the Tier 2 and the Tier 3 method for Søderberg cells are calculated according to Equation
4.24. Tier 3 requires specific operating facility data for all the components in Equation 4.24, whereas Tier 2 isbased on default values for some of the components. Section 4.4.2.2 below provides details on parameters to be
used:.
EQUATION 4.246
CO2 EMISSIONS FROM PASTE CONSUMPTION (TIER 2 AND TIER 3 METHODS)
S p + Ash p + H p⎛
CSM • MP BC
ECO 2 = ⎜⎜ PC • MP −−• PC • MP •
1000
100
100
⎝
S + Ashc
100 − BC
⎞ 44−
• PC • MP • c− MP • CD ⎟ •
100
100
⎠ 12

Where:
ECO2 = CO2 emissions from paste consumption, tonnes CO2
MP = total metal production, tonnes Al
PC = paste consumption, tonnes/tonne Al
CSM = emissions of cyclohexane soluble matter, kg/tonne Al
BC = binder content in paste, wt %Sp = sulphur content in pitch, wt %6

An acceptable alternative method is to use the parameter of 'pitch coking' in lieu of deducting measured or default values
for Sp, Hp, Ashp and CSM from Equation 4.24. The pitch coking value is a commonly determined parameter for many
facilities with Søderberg cells and standard methodology for performing the pitch coking test is described in ASTM D2416.

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Chapter 4: Metal Industry Emissions

Ashp = ash content in pitch, wt %Hp = hydrogen content in pitch, wt %Sc = sulphur content in calcined coke, wt %Ashc = ash content in calcined coke, wt %CD = carbon in skimmed dust from Søderberg cells, tonnes C/tonne Al
44/12 = CO2 molecular mass : carbon atomic mass ratio, dimensionless
Equation 4.24 should be applied to each smelter in the country using the Søderberg process and the results
summed to arrive at total national emissions. It is possible to use a hybrid Tier 2/3 approach if data on ash or
sulphur content are not available for each smelter.

4.4.2.2

C HOICE OF EMISSION FACTORS FOR CO 2 EMISSIONS FROMPRIMARY ALUMINIUM PRODUCTION

Tier 1 method for CO 2 emissions
Table 4.10 lists the default emission factors for CO2 per tonne of aluminium. The emission factors of 1.6 and 1.7
for Prebake and Søderberg technologies are based on International Aluminium Institute (IAI) global survey data
(International Aluminium Institute, Life Cycle Assessment of Aluminium , 2000).

TABLE 4.10
TIER 1 TECHNOLOGY SPECIFIC EMISSION FACTORS FOR CALCULATING CARBON DIOXIDE EMISSIONS FROM ANODE OR
PASTE CONSUMPTION

Technology

Emission Factor (tonnes
CO2/tonne Al)

Uncertainty(+/-%)

Prebake7

1.6

10

Søderberg

1.7

10

Source: International Aluminium Institute, Life Cycle Assessment of Aluminium (IAI, 2000).

Tier 2 and Tier 3 emission factors for CO 2 emissions
CO 2 emissions for Prebake cells (CWPB and SWPB):The most significant factors in Equation 4.21 are metal production and net anode consumption for Prebake
technology. Both these parameters should be collected from individual operating facilities for use with the Tier
2 or the Tier 3. Other terms in the equation make minor adjustments for non-carbon components of the anodes(for example, sulphur and ash) and thus are not as critical. Tier 3 is based on the use of specific operating
facility data for these minor components, whereas Tier 2 is based on default values listed in Tables 4.11 to 4.13.
Tier 3 improves the accuracy of the results, but the improvement in accuracy is not expected to exceed 5 percent.
Carbon consumed per tonne of aluminium produced is typically recorded by primary aluminium production
facilities given its economic significance. Facilities using prebake cells refer to this consumption as ‘net anode ornet carbon consumption,’ and those using Søderberg cells refer to it as ‘anode paste consumption.’

7

The emission factor for Prebake cells includes CO2 emissions from the combustion of pitch volatiles and packing cokefrom baking anodes.

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TABLE 4.11
DATA SOURCES AND UNCERTAINTIES FOR PARAMETERS USED IN TIER 2 OR 3 METHOD FOR CO2 EMISSIONS FROMPREBAKE CELLS (CWPB AND SWPB) , SEE EQUATION 4.21
Parameter

Tier 2 Method
Data Source

Tier 3 Method
Uncertainty(+/-%)

Data Source

Uncertainty(+/-%)

MP: total metal production(tonnes aluminium per year)

Individual facility
records2

Individual facility
records2

NAC: net anode consumption per tonneof aluminium (tonnes per tonne Al)

Individual facility
records

5

Individual facility
records

5

Sa: sulphur content in baked anodes(wt %)

Use industry
typical value, 250

Individual facility
records

10

Asha: ash content in baked anodes(wt %)

Use industry
typical value, 0.4

85

Individual facility
records

10Source: IAI (2005b).

TABLE 4.12
DATA SOURCES AND UNCERTAINTIES FOR PARAMETERS USED IN TIER 2 OR 3 METHOD FOR CO2 EMISSIONS FROM PITCH
VOLATILES COMBUSTION (CWPB AND SWPB) , SEE EQUATION 4.22
Parameter

Tier 2 Method
Data Source

Tier 3 Method
Uncertainty(+/-%)

Data Source

Uncertainty(+/-%)

GA: initial weight of green anodes
processed (tonnes green anode per year)

Individual facility
records2

Individual facility
records2

Hw: Hydrogen content in green anodes(tonnes)

Use industry
typical value,
0.005 • GA

50

Individual facility
records

10

BA: Baked anode production(tonnes per year)

Individual facility
records2

Individual facility
records

2

WT: Waste tar collected (tonnes)a) Riedhammer furnacesb) All other furnaces

Use industry
typical value,a) 0.005 • GAb) insignificant

50

Individual facility
records

20

Source: IAI (2005b).

TABLE 4.13
DATA SOURCES AND UNCERTAINTIES FOR PARAMETERS USED IN TIER 2 OR 3 METHOD FOR CO2 EMISSIONS FROM
BAKE FURNACE PACKING MATERIAL (CWPB AND SWPB) , SEE EQUATION 4.23
Parameter

Tier 2 Method
Data Source

Tier 3 Method
Uncertainty(+/-%)

Data Source

Uncertainty(+/-%)

Use industry
typical value,
0.015

25

Individual facility
records2

BA: Baked anode production (tonnes
per year)

Individual facility
records2

Individual facility
records2

Spc: Sulphur content in packing coke
(wt %)

Use industry
typical value, 250

Individual facility
records

10Ashpc: Ash content in packing coke (wt%)

Use industry
typical value, 2.5

95

Individual facility
records

10

PCC: Packing coke consumption(tonnes per tonne BA)

Source: IAI (2005b).

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Chapter 4: Metal Industry Emissions

CO 2 emissions for Søderberg cells (VSS and HSS):

The binder content in paste, BC, typically varies by less than 1 percent and is part of operation practice byfacility. It is an important term in Equation 4.24 because the carbon content of the pitch, which acts as a binder,
is lower than that of the coke, which makes up the remainder of the paste. As was noted previously for Prebake
anode consumption, the most important components of Equation 4.24 are the metal production and paste
consumption. The other terms in Equation 4.24 make small corrections based on impurities and minor
differences in carbon content of paste materials. Tier 3 is based on the use of specific operating facility data forthese minor components, whereas Tier 2 is based on default values listed in Table 4.14. Tier 3 improves theaccuracy of the results; however, the impact can be expected to be less than 5 percent on the result.

TABLE 4.14
DATA SOURCES AND UNCERTAINTIES FOR PARAMETERS USED IN TIER 2 OR 3 METHOD FOR CO2 EMISSIONS FROMSØDERBERG CELLS (VSS AND HSS)
Parameter

Tier 2 Method
Data Source

Tier 3 Method
Data
Uncertainty(+/-%)

Data Source

Data
Uncertainty(+/-%)

MP: total metal production (tonnes
Al/year)

Individual facility
records2

Individual facility
records2

PC : paste consumption(tonnes per tonne Al)

Individual facility
records

2-5

Individual facility
records

2-530

Individual facility
records

15

25

Individual facility
records

5

20

Individual facility
records

10

20

Individual facility
records

1050

Individual facility
records

10

20

Individual facility
records

1050

Individual facility
records

10

99

Individual facility
records

30

CSM: emissions of cyclohexane
soluble matter (kg per tonne Al)
BC: binder content in paste(wt %)
Sp: sulphur content in pitch(wt %)
Ashp: ash content in pitch (wt %)Hp: hydrogen content in pitch(wt %)
Sc: sulphur content in calcinedcoke (wt %)Ashc: ash content in calcined coke
(wt %)
CD: carbon in dust from anode(tonnes of carbon in skim per
tonne Al)

4.4.2.3

Use industry
typical value,
HSS – 4.0
VSS – 0.5
Use industry
typical value,
Dry Paste – 24
Wet Paste – 27
Use industry
typical value,
0.6
Use industry
typical value,
0.2
Use industry
typical value,
3.3
Use industry
typical value,
1.9
Use industry
typical value,
0.2
Use industry
typical value,
0.01

C HOICE OF METHOD FOR PFC S

During electrolysis, alumina (Al2O3) is dissolved in a fluoride melt comprising about 80 weight percent cryolite(Na3AlF6). Perfluorocarbons (CF4 and C2F6 collectively referred to as PFCs) are formed from the reaction of the
carbon anode with the cryolite melt during a process upset condition known as an ‘anode effect’. An anode effectoccurs when the concentration of alumina in the electrolyte is too low to support the standard anode reaction.

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BOX 4.2
ANODE EFFECT DESCRIPTION

An anode effect is a process upset condition where an insufficient amount of alumina is dissolvedin the electrolyte, causing voltage to be elevated above the normal operating range, resulting in theemission of PFC-containing gases.
Both Tier 2 and Tier 3 for PFCs are based on plant-specific process data for anode effects, which are regularlycollected. In choosing a method for PFCs, it should be noted that the uncertainty associated with higher tiermethodologies is significantly lower than that for Tier 1, and therefore Tier 2 and Tier 3 are strongly
recommended if this is a key category. Depending on the production technology type, the uncertainty of themethods for PFCs ranges from several hundred percent for the Tier 1 method to less than twenty percent for the
Tier 3 method. The Tier 3 methodology for PFC inventory should be utilized with slope or overvoltage
coefficients calculated from measurement data obtained using good measurement practices (U.S. EPA and IAI,
2003). Communication with primary aluminium producers will determine the availability of process data, which,in turn dictates the method used to calculate emissions. Plants routinely measure anode effect performance as
anode effect minutes per cell-day or anode effect overvoltage. PFC emissions are directly related to anode effectperformance via a coefficient, either the slope coefficient or the overvoltage coefficient.
The decision tree shown in Figure 4.12 describes good practice in choosing the PFC inventory methodology
appropriate for national circumstances. For high performing facilities that emit very small amounts of PFCs, theTier 3 method will likely not provide a significant improvement in the overall facility GHG inventory incomparison with the Tier 2 Method. 8 Consequently, it is good practice to identify these facilities prior to
selecting methods in the interest of prioritising resources. The parameters that identify these high performing
facilities depend on the type of process data collected by the facility. High performing facilities are those that
operate with less than 0.2 anode effect minutes per cell day when anode effect minutes are measured. When
overvoltage is recorded, high performing facilities operate with less than 1.4 mV overvoltage. In addition, forthese high performing facilities accurate measurement of the Tier 3 PFC coefficient is difficult because the very
low frequency of anode effects requires an extended time to obtain statistically robust results. The status of a
facility as a high performing facility should be assessed annually because economic factors, such as the restarts
of production lines after a period of inactivity, or, process factors, such as periods of power curtailments mightcause temporary increases in anode effect frequency. In addition, over time, facilities that might not at first meetthe requirements for high performers may become high performing facilities through implementation of newtechnology or improved work practices. Note that in all cases, applying different Tiers for different years will
require careful implementation to ensure time series consistency.
For all other facilities, the Tier 3 approach is preferred because plant-specific coefficients will lead to estimatesthat are more accurate. If no PFC measurements have been made to establish a plant-specific coefficient, the Tier
2 Method can be used until measurements have been made and Tier 3 coefficients are established. Countries canuse a combination of Tier 2 and Tier 3 depending on the type of data available from individual facilities.

Tier 1 method: Use of technology based default emission factors
The Tier 1 method uses technology-based default emission factors for the four main production technology types(CWPB, SWPB, VSS and HSS). PFC emissions can be calculated according to Equation 4.25. The level of
uncertainty in the Tier 1 method is much greater because individual facility anode effect performance, which is
the key determinant of anode effects and thus PFC emissions, are not directly taken into account. Tier 1 can beconsistent with good practice only when PFCs from primary aluminium is not a key category and when pertinent
process data are not available from operating facilities.

8

The levels for the process parameters that define high performing facilities for PFC emissions are the combined result of
the magnitude of, and, the uncertainty in the Tier 2 coefficient. The levels are calculated by using the positive and negative
extremes of the 95% confidence limits for the Tier 2 coefficient as a proxy for the range of likely values for Tier 3
coefficients for these facilities. The potential difference is then assessed on the overall greenhouse gas emissions from a
production facility considering both PFC and CO2 emissions. When facilities operate at or below the anode effect processparameter levels noted here for high performing facilities, the impact of moving from the Tier 2 method for PFCs to theTier 3 method would not result in a change greater than 5% in overall GWP weighted GHG emissions. PFC emissions
from high performing facilities account for less than 3% of global PFC emissions based on IAI 2004 anode effect survey
data.

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Chapter 4: Metal Industry Emissions

EQUATION 4.25
PFC EMISSIONS (TIER 1 METHOD)
ECF 4 = ∑ (EFCF 4, i • MPi )i

andEC 2 F 6 = ∑ (EFC 2 F 6, i • MPi )i

Where:
ECF4 = emissions of CF4 from aluminium production, kg CF4
EC2F6 = emissions of C2F6 from aluminium production, kg C2F6
EFCF4,i = default emission factor by cell technology type i for CF4, kg CF4/tonne Al
EFC2F6,i = default emission factor by cell technology type i for C2F6, kg C2F6/tonne Al
MPi = metal production by cell technology type i, tonnes Al

Tier 2 and Tier 3 methods: based on anode effect performance
There are two different equations for estimating individual plant CF4 emissions, which are both based on therelationship between anode effect and performance. These are the slope and overvoltage coefficient equations.
Both types of coefficients are based on direct measurements of PFCs. Tier 2 makes use of an average coefficientfrom measurements at numerous facilities while Tier 3 is based on measurements at the individual facility.
Because the process mechanisms that produce PFC emissions are similar for CF4 and C2F6, the two gases should
be considered together when estimating PFC emissions. C2F6 emissions are calculated in all the methods
described herein as a fraction of CF4 emissions.
With an established relationship between anode effect process data and PFC emissions, process data collected on
an on-going basis can be used to calculate PFC emissions in lieu of direct measurement of PFCs. The choice
between the two estimation relationships depends on the process control technology in use. Equation 4.26 should
be used when anode effect minutes per cell day are recorded and Equation 4.27 should be used when overvoltage
data are recorded.
Slope Coefficient: The slope coefficient represents the kg of CF4 per tonne of aluminium produced, divided byanode effect minutes per cell-day9. Since PFC emissions are measured per tonne of aluminium produced, it
includes the effects of cell amperage and current efficiency, the two main factors determining the amount ofaluminium produced in the cell. Equation 4.26 describes the slope method for both CF4 and C2F6.
EQUATION 4.26
PFC EMISSIONS BY SLOPE METHOD (TIER 2 AND TIER 3 METHODS)
ECF 4 = SCF 4 • AEM • MP

andEC 2 F 6 = ECF 4 • FC 2 F 6 / CF 4
Where:
ECF4 = emissions of CF4 from aluminium production, kg CF4
EC2F6 = emissions of C2F6 from aluminium production, kg C2F6
SCF4 = slope coefficient for CF4, (kg CF4/tonne Al)/(AE-Mins/cell-day)
AEM = anode effect minutes per cell-day, AE-Mins/cell-day
MP = metal production, tonnes Al
FC2F6/CF4 = weight fraction of C2F6/CF4, kg C2F6/kg CF4

9

The term ‘cell-day’ refers to the number of cells operating multiplied by the number of days of operation.

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Overvoltage Coefficient: Some process control systems characterize anode effects by calculating an Anode
Effect Overvoltage10 (AEO) statistic. AEO is defined as the extra cell voltage above the target operating voltage,
and this parameter has been shown to be a good predictor of PFC emissions when recorded by the processcontrol system. The AEO process control technology is in use at many modern smelters. AEO is calculated bysumming the product of time and voltage above the target operating voltage and dividing this figure by the timeover which data were collected.
EQUATION 4.27
PFC EMISSIONS BY OVERVOLTAGE METHOD (TIER 2 AND TIER 3 METHODS)AEO
ECF 4 = OVC •• MP
CE 100and
EC 2 F 6 = ECF 4 • FC 2 F 6 / CF 4
Where:
ECF4 = emissions of CF4 from aluminium production, kg CF4
EC2F6 = emissions of C2F6 from aluminium production, kg C2F6OVC = Overvoltage coefficient for CF4, (kg CF4/tonne Al)/mV
AEO = anode effect overvoltage, mV
CE = aluminium production process current efficiency expressed, percent (e.g., 95 percent)
MP = metal production, tonnes Al
F C2F6/CF4 = weight fraction of C2F6/CF4, kg C2F6/kg CF4

10

Computer control systems report either ‘positive’ or ‘algebraic’ overvoltage depending on the version of software used.
Use of the expression ‘overvoltage’ should not be confused with the classical electrochemical terminology, which usuallymeans the extra voltage needed for an electrochemical reaction to occur.

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Chapter 4: Metal Industry Emissions

Figure 4.12

Decision tree for calculation of PFC emissions from primary aluminium
production
Start

Are
process data
(AE minutes per cell
day or AE overvoltage)available?

Yes

Do
process data
indicate a high performing
facility?1

Yes

Calculate PFC emissions
for high performing
facilities using either
Tier 2 or Tier 3.
Box 4: Tier 3 or Tier 2

Collect
process
data5.

Yes

No

No

Are facility
specific PFC coefficientsavailable per goodpractice2?

Is this a key
category4?

Yes

Box 3: Tier 3NoNo

Calculate PFC emissions
using Tier 3 method.

Calculate PFC emissions
using Tier 2 method3.
Box 2: Tier 2

Are production
data available bytechnology?

Yes

No

Estimate annual
production by technology.

Calculate PFC emissions
using Tier 1 method6.
Box 1: Tier 1

Note:
1. High performing facilities emit so little PFCs that no significant improvement can be expected in the overall facility GHG inventory byusing the Tier 3 method rather than the Tier 2 method. High performing facilities are defined, based on what process data are collected, as
those that operate with less than 0.2 anode effect minutes per cell day, or, less than 1.4 mV overvoltage. In such facilities the improvementin accuracy in facility GHG inventory is less than 5% when moving from Tier 2 to Tier 3 methods for PFCs.
2. Good practices for obtaining facility specific PFC equation coefficients are detailed in the IAI GHG Protocol (IAI, 2005).
3. In this case, Tier 2 method should be used until site-specific Tier 3 coefficients become available and the Tier 3 method employed unless
PFC emissions become immaterial, in which case facilities can choose to use either the Tier 2 or Tier 3 method.
4. 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.
5. For key categories, it is good practice to collect anode effect process data and production activity data at the individual production
facility level.
6. Primary aluminium facilities regularly record activity data including metal production and anode effect process data facilitating, at aminimum, Tier 2 calculation method. Errors of magnitude of x10 can result from use of Tier 1 methods for PFCs.

4.4.2.4

C HOICE OF EMISSION FACTORS FOR PFC S

Tier 1: Technology based default emission factors
Default emission factors for Tier 1 method are provided in Table 4.15.

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TABLE 4.15
DEFAULT EMISSION FACTORS AND UNCERTAINTY RANGES FOR THE CALCULATION OF PFC EMISSIONS FROMALUMINIUM PRODUCTION BY CELL TECHNOLOGY TYPE (TIER 1 METHOD)
Technology

CF4
a

C2F6
EFC2F6 (kg/tonne Al)

Uncertainty Range (%)d-99/+380

0.04-99/+380

1.6-40/+150

0.4-40/+150VSS

0.8-70/+260

0.04-70/+260HSS

0.4-80/+1800.03-80/+180

EFCF4 (kg/tonne Al)

Uncertainty Range (%)

CWPB

0.4

SWPB

b

c

a

Default CF4 values calculated from median anode effect performance from 1990 IAI survey data (IAI, 2001).

b

Uncertainty based on the range of calculated CF4 specific emissions by technology from 1990 IAI anode effect survey data (IAI,
2001).

cDefault C2F6 values calculated from global average C2F6:CF4 ratios by technology, multiplied by the default CF4 emission factor.

dUncertainty range based on global average C2F6:CF4 ratios by technology, multiplied by calculated minimum and maximum specific
CF4 emissions from 1990 IAI survey data (IAI, 2001).

Note: These default emission factors should only be used in the absence of Tier 2 or Tier 3 data.

Tier 2: PFC emission factor based on a technology specific relationship between
anode effect performance and PFC emissions.
The Tier 2 method is based on using either technology specific slope or overvoltage coefficients for theapplicable reduction cell and process control technology as listed in Table 4.16.11
TABLE 4.16
TECHNOLOGY SPECIFIC SLOPE AND OVERVOLTAGE COEFFICIENTS FOR THE CALCULATION OF PFC EMISSIONS FROMALUMINIUM PRODUCTION (TIER 2 METHOD)

Technologyaa11

Slope Coefficient b, c[(kg PFC/tAl) / (AE-Mins/cellday)]Overvoltage Coefficientb, c, d[(kg CF4/tAl ) / (mV)]

Weight Fraction C2F6 / CF4

CF4

Uncertainty(+/-%)

CF4

Uncertainty(+/-%)

C2F6/CF4

Uncertainty(+/-%)

CWPB

0.143

6

1.16

24

0.121

11

SWPB

0.272

15

3.65

43

0.252

23

VSS

0.092

17

NR

NR

0.053

15

HSS

0.099

44

NR

NR

0.085

48

Centre Worked Prebake (CWPB), Side Worked Prebake (SWPB), Vertical Stud Søderberg (VSS), Horizontal Stud Søderberg (HSS).

b

Source: Measurements reported to IAI, US EPA sponsored measurements and multiple site measurements (U.S. EPA and IAI, 2003).

c

Embedded in each Slope and Overvoltage coefficient is an assumed emissions collection efficiency as follows: CWPB 98%, SWPB
90%, VSS 85%, HSS 90%. These collection efficiencies have been assumed based on measured PFC collection fractions, measured
fluoride gas collection efficiencies and expert opinion.

d

The noted coefficients reflect measurements made at some facilities recording positive overvoltage and others recording algebraic
overvoltage. No robust relationship has yet been established between positive and algebraic overvoltage. Positive overvoltage should
provide a better correlation with PFC emissions than algebraic overvoltage. Overvoltage coefficients are not relevant (NR) to VSS andHSS technologies.

These slope coefficients were derived from measurement of PFCs and correlating the measured PFC emissions to anodeeffect minutes per cell day at over one-hundred aluminium smelters. The values in Table 4.16 are the technology specificfactors from measurement data available as of March 2005 when this document was developed. It is important to note Tier
2 slope coefficients are based on the anode-effect minutes per cell-day statistic as defined in the IAI GHG Protocol (IAI,
2005a). It is good practice to refer to the most current data for calculation of PFC emissions as noted in the IAI GHG
Protocol and to the IPCC Emission Factor Database.

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Tier 3: PFC emission factor based on a facility specific relationship between
anode effect performance and PFC emissions
The Tier 3 method is based on a facility specific slope or anode effect overvoltage PFC coefficient. Thiscoefficient characterizes the relationship between facility anode effect performance and measured PFC emissions
from periodic or continuous measurements that are consistent with established measurement practices (U.S. EPA
and IAI, 2003) and the International Aluminium Institute GHG Protocol (IAI, 2005a).

4.4.2.5

C HOICE OF ACTIVITY DATA

Production statistics should be available from every facility to enable use of Tier 1 methods for both CO2 andPFC emissions. Uncertainty in the tonnes of aluminium produced is likely to be low in most countries. Given
the expected universal availability of production data, production capacity data should only be used as a checkon production statistics.
Good practice methods for PFC emissions require accurate anode effect minutes per cell day data or accurate
overvoltage (AEO) data for all cell types. Annual statistics should be based on the production-weighted averageof monthly anode effect data. Both Tier 2 and Tier 3 utilize anode effect minutes per cell day or anode effectovervoltage, and aluminium production data. Individual aluminium companies or industry groups, national
aluminium associations or the International Aluminium Institute, should be consulted to ensure that the data are
available and in a useable format for inventory estimation.
For CO2 emissions, all aluminium smelters collect data to support Tier 2 or Tier 3 methods. Søderberg smelters
collect anode paste consumption data while Prebake smelters record baked anode consumption. The Tier 2 andTier 3 methods use the same equation for calculation of CO2 emissions; however, the Tier 3 method uses facility
specific composition data for anode materials while the Tier 2 method uses industry average anode compositiondata.

4.4.2.6

C OMPLETENESS

Primary aluminium facilities will generally have good records of tonnes of aluminium produced throughout theentire time series covered by the inventory. In addition, carbon consumption data are typically available over thesame period. Anode effect process data may be incomplete over the entire time series and measures may have tobe employed, such as those described in Section 4.4.2.7, Developing a Consistent Time Series, to calculate PFC
emissions over some portions of the inventory period. Primary aluminium production also utilizes large amountof electricity and care should be exercised to avoid omissions of carbon dioxide associated with electricity input,
or, to avoid double counting of this carbon dioxide.

4.4.2.7

D EVELOPING A CONSISTENT TIME SERIES

Aluminium production statistics will typically be available for the entire history of the facility. Developing aconsistent time series for carbon dioxide emissions should not be a problem since most facilities historicallyhave measured and recorded anode or paste consumption. Where historic anode or paste consumption data are
missing, carbon dioxide emissions can be estimated from aluminium production utilizing the Tier 1 method.
A complete time series of PFC related activity data such as anode effect minutes per cell day or overvoltage
gives the best time series results. Because PFC emissions only became a major focus area in the early 1990s forthe global aluminium industry, some facilities may have limited information about the required anode effect data
to implement Tier 2 or Tier 3 PFC inventory practices over the entire time covered by the inventory. Substantial
errors and discontinuities can be introduced by reverting to Tier 1 methods for PFC emissions for years forwhich activity data are not available. The appropriateness of applying Tier 2 or Tier 3 PFC emission factors
back in time to a given facility and availability of detailed process data vary with the specific conditions.
Generally, backcasting of Tier 2 or Tier 3 methods using splicing or surrogate data are preferred over use of Tier
1 emission factors. Specifically, where only anode effect frequency data are available and anode effect duration
data are unavailable, it is good practice to splice or backcast PFC emissions per tonne aluminium based on anodeeffect frequency data. Currently many facilities are making PFC measurements that facilitate implementation ofTier 3 PFC inventory methods. There are a number of issues that impact on whether Tier 3 PFC emission factors
can be extrapolated to past inventory periods. Factors that should be considered include whether any technology
upgrades have been implemented at the facility, whether there have been substantial changes in work practices,
whether any changes in the calculation of underlying process data have occurred, and the quality of themeasurements made to establish the Tier 3 coefficients. It is good practice to consult with representatives fromthe operating facilities, either directly or through regional or international organizations representing the industry

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to develop the best strategy for the specific group of operating locations included in the national inventory.
Additional helpful information on splicing methods and details regarding constructing a time series for primaryaluminium is available from IAI (IAI, 2005). Expert advice is also available from the International Aluminium
Institute (London, UK) regarding greenhouse gas emissions and typical industry emissions from aluminium
production.

4.4.3

Uncertainty assessment

There are major differences in the uncertainty for PFC emissions depending on the choice of Tier 1, Tier 2, orTier 3 methods. The differences in uncertainty resulting from choice of method for carbon dioxide emissions aremuch smaller than for PFC emissions. There is no basis for country or regional differences in emissions resulting
from aluminium production other than the differences that result from the specific type of production
technologies and work practices in use in the country or region. These differences are reflected in the calculation
methodologies described above.

4.4.3.1

E MISSION FACTOR UNCERTAINTIESThe uncertainty in the emission factors for calculating carbon dioxide emissions from carbon anode or paste
consumption should be less than ±5 percent for both the Tier 2 and Tier 3 methods, and less than ±10 percent for
the Tier 1 method. The reactions leading to carbon dioxide emissions are well understood and the emissions arevery directly connected to the tonnes of aluminium produced through the fundamental electrochemical equations
for alumina reduction at a carbon anode and oxidation from thermal processes. Both of these fundamental
processes producing carbon dioxide are included in process parameters routinely monitored at the production
facilities, the net carbon consumed and/or paste consumption. The main source of uncertainty is in the net carbon
consumed for Prebake technologies and paste consumption for Søderberg cells. These factors are both carefully
monitored and are important factors in the economic performance of a facility. Improvements in accuracy ofcarbon dioxide emissions inventories can be achieved by moving from Tier 1 to Tier 2 methods because there isa range of performance of reduction facilities in the consumption of carbon anode materials. Less significant
improvements in accuracy can be expected in choosing the Tier 3 method over the Tier 2 method. This isbecause the major factors in the calculation are the net anode carbon consumed or paste consumption and the
production of aluminium. The uncertainty of both these components of the calculation equation is low, 2 to 5
percent, and these uncertainties dominate the overall calculation of carbon dioxide emissions in the Tier 2 andTier 3 methods. Facility specific data are used in both Tier 2 and Tier 3 calculations for these parameters. The
Tier 3 method refines the calculation to use actual composition of the carbon anode materials. While there can beconsiderable variability in the minor components of the anode materials this variability does not contributesignificantly to the overall calculation of carbon dioxide emissions.
In considering changes in uncertainty in PFC emissions inventory when moving from Tier 1 to Tier 2 and Tier 3
methods, there are major reductions in uncertainty when choosing the Tier 2 or Tier 3 methods over the Tier 1
method. The high level of uncertainty in the Tier 1 method results directly from the large variability in anodeeffect performance among operators using similar production technology. The Tier 1 method is based on using asingle default coefficient for all operators by technology type. Since there can be variations in anode effectperformance (frequency and duration) by factors of 10 among operators using the same technology (IAI, 2005c),
use of the Tier 1 method can result in uncertainties of the same magnitude. There is less impact on uncertainty
levels in choosing the Tier 3 method over the Tier 2 method; however, the level of uncertainty reduction depends
on the cell technology type. The uncertainty for industry average coefficients ranges from +/-6 percent for
CWPB, the most widely measured and used technology, to +/-44 percent for HSS. Both Tier 2 and Tier 3
methods are based on direct PFC measurements that establish a relationship between anode effect performanceand PFC specific emissions. The Tier 2 method uses an industry average equation coefficient while the Tier 3
method uses a facility specific coefficient based on direct PFC measurements made at the facility. As more
facility measurements are made, especially in those facilities operating with Søderberg technologies, theuncertainty in the average coefficients should be reduced. The lowest uncertainty for PFC emissions calculations
is from the use of the Tier 3 method. However, to achieve this lower uncertainty in Tier 3 PFC calculations it isimportant to use good practices in making facility specific PFC measurements. These measurement goodpractices have been established and documented in a protocol available globally (USEPA/IAI, 2003). When
properly established these Tier 3 coefficients will have an uncertainty of +/-15 percent at the time thecoefficients are measured.

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4.4.3.2

A CTIVITY DATA UNCERTAINTIESThere is very little uncertainty in the data for the annual production of aluminium, less than 1 percent. The
uncertainty in recording carbon consumption as baked anode consumption or coke and paste consumption isestimated to be only slightly higher than for aluminium production, less than 2 percent. The other component ofcalculated facility specific emissions using Tier 2 or Tier 3 methods is the anode effect activity data, i.e., either
anode effect minutes per cell day or anode effect overvoltage. These parameters are typically logged by theprocess control system as part of the operations of nearly all aluminium production facilities and theuncertainties in these data are low.

4.4.4
4.4.4.1

Quality Assurance/Quality Control (QA/QC),
Reporting and Documentation
Q UALITY A SSURANCE /Q UALITY C ONTROL (QA/QC)

It is good practice at all primary aluminium production facilities to maintain records of all of the necessary
activity data to support calculations of emissions factors as suggested in these guidelines. These records will
include production of aluminium, anode effect performance and consumption of carbon materials used in either
Prebake or Søderberg cells. In addition, the International Aluminium Institute maintains global summaries ofaggregated activity data for these same parameters and regional data are available from regional aluminium
associations. It is good practice to aggregate emissions estimates from each smelter to estimate total nationalemissions. However, if smelter-level production data are unavailable, smelter capacity data may be used alongwith aggregate national production to estimate smelter production.
It is good practice to verify facility CO2 emission factors per tonne aluminium by comparison with the expected
range of variation that would be predicted from the variation noted in Tables 4.10 and 4.11 for carbon dioxide
specific emissions. Also, the underlying equation coefficients used for calculating PFC emission factors per
tonne aluminium should be compared with those noted in Table 4.15. It is suggested that any inventory value
outside the 95 percent confidence range of the data population variance be confirmed with the data source.
Use of standard measurement methods improves the consistency of the resulting data and knowledge of thestatistical properties of the data. For primary aluminium, the EPA/IAI Protocol for Measurement of
Tetrafluoromethane (CF4) and Hexafluoroethane (C2F6) Emissions from Primary Aluminum Production is theinternationally recognized standard (U.S. EPA and IAI, 2003). Inventory compilers should encourage plants to
use this method for developing Tier 3 PFC equation coefficients. Significant differences between calculated
coefficients based on PFC measurements and the industry average Tier 2 coefficients for similar reduction
technology should elicit further review and checks on calculations. Large differences should be explained anddocumented. An international data set of anode effect performance, which can be used to identify outlier data, isavailable from the International Aluminium Institute. In addition, an up-to-date database of PFC measurements
is also maintained by IAI and should be consulted when assessing the appropriateness of reported data.
Inter-annual changes in emissions of carbon dioxide per tonne aluminium should not exceed +/-10 percent basedon the consistency of the underlying processes that produce carbon dioxide. In contrast, inter-annual changes inemissions of PFCs per tonne of aluminium may change by values of up to +/- 100 percent. Increases in PFC
specific emissions can result from process instability. Increases in anode effect frequency and duration can be theresult of factors such as unanticipated power interruptions, changes in sources of alumina feed materials, cell
operational problems, and increases in potline amperage to increase aluminium production. Decreases in PFC
specific emissions can result from decreases in anode effect frequency and duration due to changes in thecomputer algorithms used in cell process control, upgrades in cell technology such as the installation of point
feeders, improved work practices and better control of raw materials.

4.4.4.2

R EPORTING AND D OCUMENTATION

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Volume 1, Chapter 6, Quality Assurance and Quality Control, Internal Documentation
and Archiving. Some examples of specific documentation and reporting relevant to this source category areprovided below.
It is not practical to include all documentation in the national inventory report. However, the inventory should
include summaries of methods used and references to source data such that the reported emissions estimates are2006 IPCC Guidelines for National Greenhouse Gas Inventories

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Volume 3: Industrial Processes and Product Usetransparent and steps in their calculation may be retraced. To improve transparency, it is good practice to reportemissions for PFCs from aluminium production separately from other source categories. Additionally, it is goodpractice that CF4 and C2F6 emissions are reported separately on a mass basis.
The supporting information necessary to ensure transparency in reported emissions estimates is shown in Table
4.17, Good practice Reporting Information for PFC Emissions from Aluminium Production by Tier, below.
Much of the production and process data are considered proprietary by operators, especially where there is only
one smelter in a country. It is good practice to exercise appropriate techniques, including aggregation of data, toensure protection of confidential data.

TABLE 4.17
GOOD PRACTICE REPORTING INFORMATION FOR CALCULATING CO2 AND PFC EMISSIONS FROM ALUMINIUM
PRODUCTION BY TIER

Data

Tier 3Tier 2Tier 1

PFCs
Annual national production (by CWPB, SWPB, HSS, or VSS technology)

X

Annual production by smelter (by CWPB, SWPB, HSS, or VSS technology)

X

X

Anode Effect minutes per cell-day or Anode Effect Overvoltage (mV)X

X

Facility specific emission coefficients linked to anode effect performance

X

Technology specific emission coefficients linked to anode effect performance

X

Default technology emission coefficients

X

Supporting documentation

X

X

X

CO2
Annual national production (by Prebake or Søderberg technology)

X

Annual production by smelter (by Prebake or Søderberg technology)

X

X

Net anode consumption for Prebake cells or paste consumption for Søderberg cells

X

X

Carbon material impurity levels and carbon dust for Søderberg cells

X

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Chapter 4: Metal Industry Emissions

4.5

MAGNESIUM PRODUCTION

4.5.1

Introduction

In the magnesium industry, there are a number of potential emission sources and gases. The amount and type ofemission from the magnesium industry will reflect the raw material used for primary magnesium metal
production and/or the type of cover gas mixture used in the casting and recycling foundries to prevent oxidationof molten magnesium. It is good practice to consider, in a disaggregated way if possible, all segments of themagnesium industry and their related emissions. A list of possible greenhouse gas emissions, which may be
associated with primary, and secondary magnesium metal production and casting operations, is provided inTable 4.18.
Primary magnesium refers to metallic magnesium derived from mineral sources. Primary magnesium can beproduced either by electrolysis or a thermal reduction process. The raw materials used for primary magnesium
production are dolomite, magnesite, carnalite, serpentine, brines or seawater. Processing of carbonate raw
materials (magnesite and dolomite) will release CO2 during manufacturing. The CO2 is released during
calcination of carbonate-based ores (dolomite/magnesite) - a ‘pre-treatment’ step to the main electrolytic/thermal
reduction processes. This process is similar to the generation of CO2 in the mineral industry (see Chapter 2).
Secondary magnesium production includes the recovery and recycling of metallic magnesium from a variety ofmagnesium containing scrap materials e.g., post consumer parts, machine cuttings, casting scraps, furnace
residues, etc. Magnesium casting processes may involve metal from both primary production and secondary
magnesium production. Magnesium casting processes involve handling of molten pure magnesium and/or
molten high magnesium content alloys. Molten magnesium (also understood to mean high magnesium content
alloys) maybe cast by a variety of methods including gravity casting, sand casting, die casting and others.
All molten magnesium spontaneously burns in the presence of atmospheric oxygen. Production and casting of all
magnesium metal requires a protection system to prevent burning. Among the various protection systems
commonly used are those that use gaseous components with high GWP values, such as SF6, which typicallyescape to the atmosphere. Metallic magnesium cast from the various processes and sources all require protection
methods and will therefore have similar potentials for GHG emissions.

TABLE 4. 18
POSSIBLE GHG EMISSIONS RELATED TO PRODUCTION AND PROCESSING OF MAGNESIUM
PROCESSPOTENTIAL ASSOCIATED PROCESS GHG EMISSION
SF6

HFC’s

CO2

Others*Raw Materials Preparation for Primary Production
Dolomite/Magnesite Based

-

-

X

-

Other Raw Materials

-

-

-

-

Primary ingot casting

X

X

X

X

Die casting

X

X

X

X

Gravity casting

X

X

X

X

Other casting methods

X

X

X

X

Secondary Mg Production**

X

X

X

X

Casting (primary & secondary)*Others include fluorinated ketone and various fluorinated decomposition products e.g., PFCs** Includes processes involving the recycle/recovery of metallic magnesium

Secondary magnesium production (recycling), handling, melting, and casting, molten metal is protected against
oxidation throughout the process by using protection systems such as SF6 or SO2 containing cover gases (a2006 IPCC Guidelines for National Greenhouse Gas Inventories

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carrier gas (commonly air and/or CO2) and SF6 or SO212) or, in some cases, flux. High-magnesium content alloys
are also commonly protected using SF6 containing cover gases. Due to recent technological developments and apush towards the replacement of SF6, the magnesium industry has introduced alternative cover gases. It is
foreseen that the two most common alternatives to SF6 in the next decade will be the fluorinated hydrocarbon
HFC-134a and the fluorinated ketone FK 5-1-12 (C3F7C(O)C2F5), traded under the name Novec™61213, and thatthe individual magnesium producer’s/processor’s choice of cover gas will be strongly influenced bynational/regional circumstances (Tranell et al., 2004).

CO 2 EMISSIONS FROM PRIMARY PRODUCTION
As indicated in Table 4.18, the magnesium-containing ores which release CO2 during calcination are dolomite(Mg•Ca(CO3)2) and magnesite (MgCO3). For each kilogram of magnesium produced, theoretically 3.62 kg14
(dolomite) or 1.81 kg (magnesite) respectively of CO2, is emitted during calcination. The actual CO2 emissions
per kilogram magnesium produced will be higher than the theoretical emission due to losses of magnesium in theprocess chain.

MAGNESIUM CASTING PROCESSES (PRIMARY & SECONDARY)In magnesium casting processes, the size and type of GHG emission will depend on the chosen cover gas systemused to protect liquid magnesium. In addition to emissions of the active protection compound (SF6, HFC-134a
or FK 5-1-12) in the cover gas itself – there may be emissions of various fluorinated decomposition products(e.g., PFCs) and potentially also the carrier gas (depending on choice of air and/or CO2 or N2).

SF 6
It has been a common assumption that SF6 in magnesium cover gas is inert and that hence, essentially all SF6
used in the magnesium industry will be emitted. However, recent independent studies (Bartos et al., 2003 andTranell et al., 2004) demonstrate that SF6 does, to a certain degree, destruct in contact with liquid/gaseous
magnesium at common magnesium holding/processing temperatures. The fraction of SF6 destroyed in the
furnace, as well as the type/amount of secondary gas products generated from the reaction with magnesium, will
depend on pertaining operating conditions such as SF6 concentration in cover gas, total cover gas flow-rate, sizeof reactive magnesium surface area, type of carrier gas used, furnace charging practises, etc.

HFC-134a, FK 5-1-12 and decomposition products (e.g., PFCs)
Both HFC-134a and FK 5-1-12 are less thermodynamically stable (and thus have much lower GWP) than SF6. It
is hence expected that these gases will decompose/react extensively in the contact with liquid/gaseous
magnesium, leading to the production of various fluorinated gases (e.g., PFCs). Tranell et al., 2004 found that asa general rule of thumb, when SF6 is replaced by HFC-134a, less than half the amount of active fluorinatedcompound on a molar basis is needed to protect a given magnesium surface (under otherwise identicalconditions). When SF6 replaces FK 5-1-12, less than a quarter of the quantity of active compound is needed. It
was reported that, as is the case for SF6, the amount of active compound in the in-going cover gas destroyed in
the furnace depends on conditions such as compound concentration in in-going cover gas, total cover gas flowrate, size of reactive magnesium surface area, type of carrier gas used, charging practises etc. It should be notedthat emissions of PFCs as decomposition products would be more significant in terms of CO2 equivalent than FK
5-1-12 emissions, given their relative radiative effects15.

Carrier gases
Many cover gas systems use CO2 as a carrier gas -alone or in combination with dry air- to dilute the active
fluorinated compound and reduce the oxygen partial pressure in the furnace. It is a quantitatively reasonableassumption that all CO2 used in the cover gas is emitted as CO2. The amount of carbon dioxide cover gas used ismuch lower than the usual active agents in the cover gas system and can generally be disregarded.

12

Consistent with the scope of these Guidelines outlined in Volume 1, this chapter does not provide methods for estimating
emissions of SO2.

13

FK 5-1-12 (C3F7C(O)C2F5), traded as Novec™612, is a fluorinated ketone produced by 3M (Milbrath, 2002).

14

This represents a case where the ore has a stoichiometric Mg/Ca ratio of 1.

15

The GWP value of FK 5-1-12 is not identified in the IPCC Third Assessment Report (IPCC, 2001), but it is estimated to be
similar to that of CO2 according to the producer of this gas.

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Chapter 4: Metal Industry Emissions

4.5.2

Methodological issues

4.5.2.1

C HOICE OF METHOD

CO 2 EMISSIONS FROM PRIMARY PRODUCTION
The choice of a good practice method for inventory preparation of carbon dioxide emissions from the primarymagnesium (raw material) production segment will depend on national circumstances. The decision tree (seeFigure 4.13, Decision Tree for Estimation of CO2 Emissions from Primary Magnesium Production) describes
good practice in adapting the methods to these country-specific circumstances.

Tier 1The Tier 1 method relies on national primary production data and knowledge of raw materials used in the
country. National production data may not be publicly available as there are a limited number of countries
producing magnesium and only a few individual producers - often only one in a country - often resulting in thedesignation of national production data as confidential. In the absence of national primary magnesium
production statistics, industry associations, such as the International Magnesium Association(http://www.intlmag.org/), may be able to provide regional statistics. Failing other data, it may be possible toestimate primary magnesium production from annual national magnesium metal sales. This method has
increased uncertainty, since it does not account for magnesium used in national product manufacturing.
CO2 emissions are calculated using Equation 4.28.
EQUATION 4.28
CO2 EMISSIONS FROM PRIMARY MAGNESIUM PRODUCTION (TIER 1)()

ECO 2 = Pd • EFd + Pmg • EFmg • 10 −3

Where:
ECO2 = CO2 emissions from primary magnesium production, Gg
Pd = national primary magnesium production from dolomite, tonnes
Pmg = national primary magnesium production from magnesite, tonnes
EFd = Default emission factor for CO2 emissions from primary magnesium production from dolomite,tonne CO2/tonne primary Mg produced
EFmg = Default emission factor for CO2 emissions from primary magnesium production from magnesite,
tonne CO2/tonne primary Mg produced

Tier 2The Tier 2 method for determining CO2 emissions from primary magnesium involves collecting company/plantspecific empirical emission factors, in addition to company specific production data. The company specificemission factors may differ substantially from the default emission factors depending on process materials
handling. This collection should take place if the emissions are a key category.
CO2 emissions are calculated using Equation 4.29.
EQUATION 4.29
CO2 EMISSIONS FROM PRIMARY MAGNESIUM PRODUCTION (TIER 2)
ECO 2 = ∑ ( Pi • EFi ) • 10 −3iWhere:
ECO2 = CO2 emissions from primary magnesium production, Gg
Pi = primary magnesium produced in plant i, tonne
EFi = company/plant-specific emission factor for CO2 emissions from primary magnesium production
obtained from company/plant i, tonne CO2 /tonne primary Mg produced

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Tier 3
If actual measured CO2 emissions data are available from individual primary magnesium facilities, these data
can be aggregated and used directly to account for national emissions.

MAGNESIUM CASTING PROCESSES (PRIMARY & SECONDARY)
SF 6
The choice of a good practice method for inventory preparation of SF6 emissions from magnesium castingprocess segment will also depend on national circumstances. The decision tree (Figure 4.14, Decision Tree for
Estimation of SF6 Emissions from Magnesium Processing) describes good practice in adapting the methods tothese country-specific circumstances.

Tier 1 – default emission factors
The Tier 1 method is based on the total amount of magnesium casting or handling in the country (Equation 4.30).
The underlying assumption for the Tier 1 approach is that all SF6 consumption in the magnesium industry
segment is emitted as SF6. As described in Section 4.5.1, this assumption will potentially overestimate the GHG
emissions, but the overestimate will lie within the overall uncertainty range given in Section 4.5.3. The basic
Tier 1 method uses a single value as a basis for the default emission calculation when SF6 is used for oxidation
protection, despite the fact that SF6 consumption vary substantially between different casting operations andoperators (sometimes orders of magnitude). The Tier 1 method should be used only when the inventory compiler
has no knowledge of type of magnesium handling- or casting operation (recycling, billet casting or die-castingetc.)
EQUATION 4.30
SF6 EMISSIONS FROM MAGNESIUM CASTING (TIER 1)
E SF 6 = MGc • EFSF 6 • 10 −3

Where
ESF6 = SF6 emissions from magnesium casting, tonnes
MGc = total amount of magnesium casting or handling in the country, tonnes
EFSF6 = default emission factor for SF6 emissions from magnesium casting, kg SF6/tonne Mg casting

Tier 2 – company-specific SF 6 consumption

As for the Tier 1 method, the Tier 2 method also assumes that all SF6 consumed is subsequentlyemitted. Insteadof the amount of magnesium casting, however, the Tier 2 method uses data on national (or sub-national)
consumption of SF6 in the magnesium industry as reported by the industry or available through other sources
such as national statistics (Equation 4.31).
The most accurate application of the method is normally collection of direct data on SF6 consumption from allindividual users of the gas in the magnesium industry. If no direct data are available, an alternative but a lessaccurate method is to estimate the share of annual national SF6 consumption attributable to the magnesium
industry. This requires collecting annual data on national SF6 sales and assumes that all SF6 gas sold to themagnesium industry is emitted within the year.
EQUATION 4.31
SF6 EMISSIONS FROM MAGNESIUM CASTING (TIER 2)
E SF 6 = C SF 6

Where
ESF6 = SF6 emissions from magnesium casting, tonnes
CSF6 = consumption of SF6 in magnesium smelters and foundries, tonnes

Tier 3 – direct measurement approachIf actual measured emission data are available from individual magnesium processing facilities, these data can be
aggregated and used directly to account for national emissions. In such reporting, it is good practice to include
destruction of SF6 and formation of secondary gas products.

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Chapter 4: Metal Industry Emissions

Figure 4.13

Decision tree for estimation of CO 2 emissions from raw materials calcinationin the primary magnesium production process
Start

Are
carbonate raw
materials used for primary
Mg production?

No

Report ‘Not occurring’

Yes

Estimate emissions using
the direct reporting method.

Yes

Are there
direct reported data on CO2emissions?

Box 4: Tier 3
No

Are there
country/company-specificemission factors and production
data available fromcompanies?

Estimate emissions using
country/company-specificemission factors andproduction data (direct
and top-down) method.

Yes

Box 3: Tier 2
No

Is this a key
category1?

NoIsnational primary Mg
production data and raw
material source(s)known?

Yes

Estimate emissions using
default emission factors.
Box 2: Tier 1

Yes
Collect data for the Tier 3or the Tier 2 method

No

Estimate emissions using
the national sales method.
Box 1: Tier 1

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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Figure 4.14

Decision tree for estimation of SF 6 emissions from magnesium processing
Start

Identify segments of theMagnesium Industry.

For eachsegment, is SF6 used as acover gas?

No

Continue to the next segment.
If ‘No’ for all segments,
report ‘Not occuring’.

Yes

Estimate emissions using
the direct reporting method.

Yes

Are there
direct measured
emission data related
to SF6 use?

Box 4: Tier 3

No

Are therereported data on
SF6 use from any
segments?

Report emissions as equalling
all SF6 use in segment.

Yes

Box 3: Tier 2

No

Is this a key
category1?

No

Are
there activity leveland emission factor
data?

Yes

Estimate emissions based on
activity level and countryspecific or default emission
factors.
Box 2: Tier 1

Yes
Collect data for the Tier 3or the Tier 2 method

No

Estimate emissions using
national statistics anddefault emission factor.
Box 1: Tier 1

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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Chapter 4: Metal Industry Emissions

HFC-134a, FK 5-1-12 and decomposition products (e.g., PFCs)
As described in Section 4.5.1, the industrial use of fluorinated compounds other than SF6 for magnesiumoxidation protection commenced in 2003-2004. As such, the industrial experience in using these compounds formagnesium protection purposes is yet very limited. Even individual plants will have little historic data, if any, on
actual emissions of these other fluorinated compounds from their operations. While there is a general sense inindustry that the volume use of these alternate gases will be less than SF6, there are no data available at this timeon which to base emission factors. Hence, it is not possible at this time to develop an emission factor-based
approach (Tier 1 or 2) for reporting emissions.
However, if the GHG emission from the use of magnesium cover gases is a national key category, it is goodpractice to collect direct measurements or meaningful indirect measurements of GHG emissions (fugitive
emissions of HFC134-a and FK 5-1-12 as well as emissions of PFCs as decomposition products) frommagnesium foundries using HFC-134a or FK 5-1-12 as cover gases. This is consistent with the Tier 3 approach.

Carrier gases
The contribution of carbon dioxide carrier gas used in protective cover gas systems is normally a small fractionof the global warming potential. In general, these emissions may be disregarded.

4.5.2.2

C HOICE OF EMISSION FACTORSCO 2 EMISSIONS FROM PRIMARY PRODUCTION
Tier 1 – default emission factors
As previously mentioned, the Tier 1 method calculates emissions from default emission factors applied to a
country’s total primary magnesium production. The default emission factors (Table 4.19) take into account thetype of material used and basic stoichiometric ratios which have been adjusted by empirical data for genericmanufacturing process losses. The resulting emission of CO2 per tonne magnesium produced is considerably
higher than the theoretical volume described in the Section 4.5.1.

TABLE 4.19
EMISSION FACTORS FOR ORE-SPECIFIC PRIMARY Mg METAL PRODUCTION
Raw Material

tonnes CO2 emission/tonne primary Mg produced

Dolomite

5.13

Magnesite

2.83

Tier 2 – country/company-specific emission factors
The Tier 2 method for estimating CO2 emissions from primary magnesium involves collecting company/plantspecific empirical emission factors. The company specific emission factors may differ substantially from thedefault emission factors depending on process materials handling. This collection should take place if theemissions are a key category.

Tier 3 – direct measurement approachIf actual measured CO2 emissions data are available from individual primary magnesium facilities, these data
can be aggregated and used directly to account for national emissions.

MAGNESIUM CASTING PROCESSES (PRIMARY & SECONDARY)SF 6Tier 1 – default emission factors
The underlying assumption for the Tier 1 approach is that all SF6 consumption in this industry segment isemitted, though. as described in Section 4.5.1, this assumption will potentially overestimate the GHG emissions.
The Tier 1 method also assumes no knowledge of type of magnesium handling- or casting operation (recycling,billet casting or die-casting, etc.) Under recommended conditions for die-casting, the consumption rates areabout 1 kg SF6 per tonne magnesium produced or smelted (Gjestland and Magers, 1996). Although the SF62006 IPCC Guidelines for National Greenhouse Gas Inventories

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consumption vary substantially between different casting operations and operators (sometimes orders ofmagnitude), the basic Tier 1 method uses this value as a basis for the default emission calculation when SF6 isused for oxidation protection. If the national magnesium manufacturing processes are well documented, a moreaccurate application of the Tier 1 method is to disaggregate production data and emission factors according to
the various manufacturing processes. These emission factors should relate SF6 emissions to magnesium
production at the same disaggregated level as the available activity data (e.g., national, sub-national). Nationalemission factors based on plant measurements are preferable to international default factors because they reflect
conditions specific to the country. Such information may be accessible through industry associations, surveys or
studies.

TABLE 4.20
SF6 EMISSION FACTORS FOR MAGNESIUM CASTING PROCESSES (TIER 1)
Casting system

kg SF6 emission per tonne Mg casting

All Casting Processes

1.0

Source: Gjestland and Magers (1996)

Tier 2 – company-specific SF 6 consumption

As for the Tier 1 method, the underlying principle for the Tier 2 method is that all SF6 consumed is emitted. In
the Tier 2 method it is, however, assumed the national (or sub-national ) consumption of SF6 in the magnesium
industry is reported by the industry or available through other sources such as national statistics.
The most accurate application of the method is normally collection of direct data on SF6 consumption from allindividual users of the gas in the magnesium industry. If no direct data are available, an alternative but a lessaccurate method is to estimate the share of annual national SF6 consumption attributable to the magnesium
industry. This requires collecting annual data on national SF6 sales and assumes that all SF6 gas sold to themagnesium industry is emitted within the year.

Tier 3 – direct measurement approachIf actual measured emission data are available from individual magnesium processing facilities, these data can be
aggregated and used directly to account for national emissions. In such reporting, it is good practice to include
destruction of SF6 and formation of secondary gas products.

HFC-134a, FK 5-1-12 and decomposition products (e.g., PFCs)
As described above, there are little historic data upon which to base emission factors. However, if the GHG
emission from the use of magnesium cover gases is a national key category, it is good practice, for inventory
preparation purposes, to collect direct measurements and or reliable indirect measures of GHG emissions(fugitive emissions of HFC134-a and FK 5-1-12 as well as emissions of PFCs as decomposition products) frommagnesium foundries using HFC-134a or FK 5-1-12 as cover gases. This may be considered a Tier 3 approach.
Over time, it may be possible to use Tier 3 measurements as a means of developing emission factors that could
be used for Tier 2.

Carrier gases
As mentioned previously in this chapter, the contribution of carbon dioxide carrier gas used in protective covergas systems is normally a small fraction of the global warming potential. In general it may be disregarded.

4.5.2.3

C HOICE OF ACTIVITY DATA

CO 2 EMISSIONS FROM PRIMARY PRODUCTION
For the Tier 1 method, inventory compilers need to obtain national primary production data and knowledge ofraw material type used in the country. As discussed in Section 4.5.2.1, these data may not be publicly available
and therefore be difficult to obtain, in particular for small-scale (particularly thermal reduction type) production
units in developing countries. Approximate national magnesium production data may be available throughindustry associations such as the International Magnesium Association. For the Tier 2 method, inventory

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Chapter 4: Metal Industry Emissions

compilers need to collect primary magnesium production data and data on carbonate raw materials from eachcompany/plant. With the Tier 3 method, activity data consists of direct measured and reported emissions.

MAGNESIUM CASTING PROCESSES (PRIMARY & SECONDARY)SF 6For the Tier 1 method, it is good practice to disaggregate production data into segments using SF6, if possible,(e.g., primary production, recycling, billet casting, die casting, gravity casting, etc.) and apply available segmentspecific emission factors. Where disaggregated data are not available, more aggregated production data, possibly
combining output from several different processes, may be used to provide an estimate. In the absence of SF6
consumption data or magnesium production data, the alternative is to collect annual national data on SF6 sales tothe magnesium industry. SF6 producers may be able to provide these data directly, or they may be available fromnational statistics. It is good practice to consider data on consumption by other industries that use SF6 (e.g.,
electrical equipment) when estimating the share consumed by the magnesium industry.
With the Tier 3 and 2 methods, the activity data are reported SF6 (and secondary gas product) emissions or SF6
consumption totals from each plant. For the Tier 1 method, national- or individual plant- magnesium production
data are necessary. Where there is some direct reporting of SF6 use in a segment, it is good practice to assess theshare of production represented by the plants that directly report. For the other plants, it is good practice to use
production-based estimates of emissions.

HFC-134a, FK 5-1-12 and decomposition products (e.g., PFCs)
With the Tier 3 method, activity data consists of direct measured and reported emissions. No Tier 1 or 2 method
guidance is provided and hence, no activity data are necessary.

Carrier gases
It is good practice in inventory reporting that the chosen activity data for carrier gases are analogous to those of
the active compound used. I.e., if CO2 is used as carrier gas for SF6, the activity data of CO2 should reflect that of
SF6. If CO2 is used as carrier for HFC-134a or FK 5-1-12, CO2 activity data should reflect HFC-134a or FK 5-112 activity data.

4.5.2.4

C OMPLETENESS

Incomplete direct reporting or incomplete activity data should not be a significant issue for primary production
in developed countries. Typically, there are a small number of well-known primary magnesium producers indeveloped countries, and these producers are likely to keep good records. In developing countries, completenessissues generally arise in the casting segments, where facilities are more widely distributed, and have a wide
range of capacities and technologies. Some plants may supply to niche markets not captured by national data sets.
The inventory compiler should confirm the absence of estimates for these smaller industry segments rather thansimply assuming they do not occur. It is also good practice to undertake periodic surveys of the industry andestablish close links with international and local industry associations to check completeness of estimates.
Because alternate (non-SF6) cover gas systems decompose to various fluorinated by-products, there may be someunaccounted global warming potential not described. This is not expected to be significant.
Since an increasing fraction of the world’s primary production, as well as processing of magnesium, takes placein many small production units in countries with developing economies, completeness is expected to become asignificant issue.
Inventory compilers should be cautious of the potential for double counting emissions from calcination ofmagnesium carbonate raw materials during primary magnesium production and those emissions associated withcalcining limestone, dolomite, and other carboneous minerals (see Chapter 2, Other Process Uses of Carbonates,in this volume.) All emissions associated with the calcination of carbonates for primary magnesium production
should be reported as GHG emissions from magnesium production.

4.5.2.5

D EVELOPING A CONSISTENT TIME SERIESIn terms of overall magnesium production statistics, these data will typically be available for the history of aplant. However, in some cases, historical production data may not be available due to lack of initial records orchanges in the structure of the industry in the intervening period. In this case, production data from internationalsources may be used.

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There may be issues with establishing a consistent time series for CO2 emissions from primary magnesium
production since these emissions may not have been reported prior to year 2006 (guidelines for reporting did notexist in the Revised 1996 IPCC Guidelines (IPCC, 1997)). For most primary magnesium production facilities it
may, however, be assumed that the CO2 emission level is relatively constant over time on a per tonne
magnesium produced basis.
In terms of SF6 emissions, it is good practice for the Tier 1 approach to multiply historic activity data by subnational/national or default emission factor presently in use to establish consistent time series. It should be notedthat plant specific emission factors would typically decrease over time due to environmental awareness,
economic factors, and improved technologies and practices.
Since the magnesium industry did not use HFC-134a and FK 5-1-12 cover gases to a significant extent in any
country prior to 2003, historic emissions will likely be zero. Given the level of complexity in reporting emissions
related to the use of these gases, developing consistent time series will be a challenge to inventory compilers.
It is good practice to assess the appropriate historical emission factors following the guidance in Volume 1,
Chapter 5. To ensure consistency over time, it is good practice to recalculate emissions estimates using
previously used and new methods to ensure that any trends in emissions are real and not caused by changes inthe estimation methodologies. Good practice is to document assumptions in all cases and archive them at theinventory compiler.

4.5.3

Uncertainty assessment

CO 2 EMISSIONS FROM PRIMARY PRODUCTION
At the plant level, there should normally be well-documented raw material type/analysis and use, as well as
tonnage magnesium produced. Directly-reported activity data, which are required for Tier 2 and 3 methods for
all gases, are typically accurate to within less than 5 percent. At the national inventory level, the accuracy ofmagnesium production activity and emission data is comparable to that of other national production statistics(i.e., ±5 percent). Additional uncertainty is introduced through estimating the share of production not reporting
directly.

MAGNESIUM CASTING PROCESSES (PRIMARY & SECONDARY)SF 6
In the Tier 1 approach, aggregating production from different secondary segments and using the default emission
factor introduces uncertainty. For example, national data from casting operations may not be segregated into diecasting and gravity casting segments despite their potentially different SF6 emission rates. Thus, this approachgives by default a very rough approximation of real emissions. Given that different handling and casting
operations may use concentrations of SF6 in cover gas that differ by orders of magnitude, uncertainties using theTier 1 method may also range over orders of magnitude. For the Tier 1 and 2 methods, there is also a level of
uncertainty associated with the assumption that 100 percent of the SF6 used is emitted. In a typical casting
operation, the uncertainty in this assumption should be within 30 percent (Bartos et al., 2003).
For the Tier 2 method, there is a very low uncertainty associated with SF6 use on a plant level, since SF6 use ismeasured easily and accurately from purchase data. (An uncertainty estimate of less than 5 percent is usually
appropriate for directly reported data.)

For the Tier 3 method, uncertainties arise mainly from monitoring equipment calibration/accuracy. Typical gas
analysis methods such as Fourier Transformed Infra Red Spectroscopy (FTIR) generally operate with anestimated accuracy of ± 10 percent. In addition to FTIR and similar analytical techniques, there will be further
uncertainty caused by problems related to representative sampling and calibration that could raise the overall
uncertainty of FTIR to ± 20 percent.

HFC-134a, FK 5-1-12 and decomposition products (e.g., PFCs)
As with the Tier 3 method for SF6, main uncertainties are associated with monitoring equipment
calibration/accuracy in processes using HFC-134a or FK 5-1-12 cover gases. Uncertainties are approximated to± 10 percent.

Carrier gases
The largest uncertainty is associated with the Tier 1 approach of considering CO2 emissions from cover gases
negligible. This is particularly true if a facility uses a very CO2 rich carrier gas blend. Other tiers have the same
uncertainties as related for SF6.

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4.5.4

Quality Assurance/Quality Control (QA/QC),
Reporting and Documentation

4.5.4.1

Q UALITY A SSURANCE /Q UALITY C ONTROL (QA/QC)

It is good practice to conduct quality control checks as outlined in Volume 1, Chapter 6, and an expert review ofthe emissions estimates. Additional quality control checks, as outlined in Volume 1, Chapter 6, and quality
assurance procedures may also be applicable, particularly for higher tier methods. Inventory compilers areencouraged to use higher tier QA/QC for key categories as identified in Volume 1, Chapter 4.
The following section outlines additional procedures specific to magnesium production:

Comparison of emissions estimates using different approaches
If emissions were calculated using data from individual plants, inventory compilers should compare the estimate
to emissions calculated using national magnesium production data or (in the case of SF6) national consumption
data attributed to magnesium use. The results of the comparison should be recorded and any discrepancies
should be investigated.

Review of plant-level data
The following plant-specific information should be archived to facilitate independent review:•

Magnesium production volumes and process types;•

Cover gas with global warming potential (SF6, HFC-134a, FK 5-1-12, CO2, etc.) consumption/compositionor magnesium production (where factors are used);•

Plant-level QA/QC results (including documentation of sampling, measurement method, and measurement
results for plant level data);•

Results of QA/QC conducted by any integrating body (e.g., industry association such as the International
Magnesium Association.);•Calculations and estimation method; and•Where applicable, a list of assumptions in allocating national SF6 usage, HFC-134a, FK 5-1-12 or othercover gases of interest or production to plant level.

Inventory compilers should determine if national or international measurement standards were used for reportingof global warming cover gas (SF6, HFC-134a, FK 5-1-12, etc.) consumption or magnesium production data at theindividual plants. If standard methods and QA/QC procedures were not followed, then use of these activity data
should be reconsidered.

Review of national activity data
QA/QC activities associated with the reference to magnesium production data should be evaluated andreferenced. Inventory compilers should check if the trade association or agency that compiled the national
production data used acceptable QA/QC procedures. If the QA/QC procedures are deemed acceptable, inventory
compilers should reference the QC activity as part of the QA/QC documentation.

Assessment of emission factors
Where company/country-specific factors are used, inventory compilers should review the level of QC associatedwith the underlying data. It is good practice that the inventory compiler cross-check national level default factors
against plant-level factors to determine if these are representative.

Peer review
Inventory compilers should involve magnesium industry experts in a thorough review of the inventory estimate,giving consideration to potential confidentiality issues. Historical production data may be less sensitive to public
disclosure than current data and could be utilised for an external peer review of plant level emissions.

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Verification of SF 6 emissions data
Inventory compilers should sum the amount of SF6 used by different industrial sectors (e.g., magnesium,
electrical equipment) and compare this value with the total usage of SF6 in the country, obtained fromimport/export and production data. This provides an upper bound on the potential emissions.16

4.5.4.2

R EPORTING AND D OCUMENTATION

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Volume 1, Section 6.11. It is not practical to include all documentation in the national
inventory report. However, the inventory should include summaries of methods used and references to source
data such that the reported emissions estimates are transparent and steps in their calculation may be retraced.
To improve transparency, it is good practice to report emissions estimates from the magnesium source category
separately by industry segments such as primary production, secondary production and casting.
The following additional information can provide a reasonable degree of transparency in reporting:Direct reporting•

Number of magnesium plants reporting;•

The types of processes and manufacture employed;•

Magnesium and magnesium products produced;•

SF6 emissions associated with the magnesium segment;•

Use of other protective cover gases with global warming potential; and•Emission factor data (and reference) for each protective cover gas with global warming potential.

National cover gas sales-based estimate of potential emissions•

National SF6 consumption (and reference);•

National use of HFC-134a assigned to the magnesium sector;•

National use of FK 5-1-12 assigned to the magnesium sector;•

Assumptions for allocating SF6 , HFC-134a, FK 5-1-12, used to magnesium;•

Estimate of percentage of national SF6, HFC-134a, FK 5-1-12, used in magnesium (and reference); and•Any other assumptions made.

In most countries, the magnesium industry will be represented by a small number of plants. In this industry, theactivity level data and cover gas emissions (that are directly related to activity levels) may be considered
confidential business information and public reporting may be subject to confidentiality considerations.

16

It may not always be the case that such aggregated consumption data will provide an upper limit on emissions. It is
possible, depending on the national characteristics of the SF6 consuming industry that in some years actual emissions of
SF6 may be greater than consumption of SF6. For instance, consumption in die casting of magnesium may be very low,
there may not be much semiconductor manufacturing, but a considerable bank of SF6 in electrical equipment may have
evolved through the years. In this case, leakage from bank combined with emissions resulting from decommissioning ofequipment may lead to actual emissions that exceed consumption of SF6 (potential emissions). See also Section 8.2 on SF6emissions from electrical equipment.

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4.6

LEAD PRODUCTION

4.6.1

Introduction

PRIMARY PRODUCTION PROCESSES
There are two primary processes for the production of rough lead bullion from lead concentrates. The first typeis sintering/smelting, which consists of sequential sintering and smelting steps and constitutes roughly 78 percentof the primary lead production. The second type is direct smelting, which eliminates the sintering step andconstitutes the remaining 22 percent of primary lead production in the developed world. (Sjardin, 2003)
In the sintering/smelting process, the initial sintering blends lead concentrates with recycled sinter, lime rock andsilica, oxygen, and high-lead-content sludge to remove sulphur and volatile metals via combustion (MetallurgicalIndustry, 1995). The process, which produces a sinter roast that consists of lead oxide and other metallic oxides,
results in the emission of sulphur dioxide (SO2) and energy-related carbon dioxide (CO2) from the natural gas
used to ignite the lead oxides (DOE, 2002). The sinter roast is then put in a blast furnace along with ores
containing other metals, air, smelter by-products, and metallurgical coke (Metallurgical Industry, 1995). The
coke burns as it reacts with air and produces carbon monoxide (CO) that actually performs the reduction of thelead oxide by chemical reaction (DOE, 2002). The smelting process occurs in either a traditional blast furnace oran Imperial Smelting Furnace, and it is the reduction of the lead oxide during this process that produces CO2
emissions (Sjardin, 2003). The sintering process produces molten lead bullion (Metallurgical Industry, 1995).
In the direct smelting process, the sintering step is skipped, and the lead concentrates and other materials areentered directly into a furnace in which they are melted and oxidized (Sjardin, 2003). A variety of furnaces areused for the direct smelting process, with the Isasmelt-Ausmelt, Queneau-Schumann-Lurgi, and Kaldo furnaces
used for bath smelting and the Kivcet furnace used for flash smelting. A number of reducing agents, which
include coal, metallurgical coke, and natural gas, are used in the process in different quantities for each furnace,
which results in different levels of CO2 emissions for each type of furnace (Sjardin, 2003; LDA, 2002). The
direct smelting process offers significant environmental and potential cost saving benefits through the avoidanceof the sintering process and is therefore expected to constitute a growing portion of primary refinery leadproduction in the future (LDA, 2002).

SECONDARY PRODUCTION PROCESSThe secondary production of refined lead amounts to the processing of recycled lead to prepare it for reuse. The
vast majority of this recycled lead comes from scrapped lead acid batteries. The lead acid batteries are either
crushed using a hammer mill and entered into the smelting process with or without desulphurization or they are
smelted whole (Sjardin, 2003). Traditional blast furnaces, Imperial Smelting Furnaces, electric arc furnaces,
electric resistance furnaces, reverbatory furnaces, Isasmelt furnaces, Queneau-Schumann-Lurgi furnaces, andKivcet furnaces can all be used for the smelting of these batteries and other recycled scrap lead (Sjardin, 2003).
As with the furnaces used for primary lead bullion production, these furnaces generate different levels of CO2
emissions from their use of differing types and quantities of reductants. The primary reductants are coal, naturalgas, and metallurgical coke, although the electric resistance furnace uses petroleum coke (Sjardin, 2003).

4.6.2

Methodological Issues

4.6.2.1

C HOICE OF METHODThe IPCC Guidelines outline three methods for calculating CO2 emissions from lead production. The choice of agood practice method depends on national circumstances as shown in the decision tree in Figure 4.15. The Tier 1
method calculates emissions from general emission factors applied to a country’s total lead production and is theleast accurate. This method is appropriate only when lead production is not a key category. The Tier 2 method
uses country specific process material data for both primary and secondary production processes multiplied by
the appropriate carbon contents of process materials. The Tier 3 method requires facility-specific measured
activity or emissions data.

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Figure 4.15

Decision tree for estimation of CO 2 emissions from lead production
Start

Are plantspecific emissions
or activity data
available?

Yes

Calculate emissions
using plant specific data.
Box 3: Tier 3

No

Are national
process material
data available?

Yes

Calculate emissions
using process material
specific carbon contents.
Box 2: Tier 2

No

Is this a key
category1?

No

Calculate emissions
using default emission
factors and national
production data.
Box 1: Tier 1

Yes
Collect data for the Tier 3or the Tier 2 method.
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 simplest estimation method is to multiply default emission factors by lead production. When the only data
available are national lead production statistics, it is good practice to use default emission factors. Equation 4.32
calculates total carbon dioxide emissions from lead production by summing emissions by source and accounting
for emissions from secondary feedstock pre-treatment. If it is not possible to differentiate the type of production
process, the default emission factor should be used. The default emission factor assumes a that 80 percent of
production (including both primary and secondary) is smelted using an Imperial Smelting Furnaces or blast
furnaces, while the remaining 20 percent is smelted using the direct smelting method in the Kivcet, Ausmelt, andQueneau-Schumann-Lurgi furnaces. This assumption is consistent with global lead production data (Sjardin,
2003).
EQUATION 4.32
CO2 EMISSIONS FROM LEAD PRODUCTION
E CO 2 = DS • EFDS + ISF • EFISF + S • EFS

Where:
ECO2 = CO2 emissions from lead production, tonnes
DS = quantity of lead produced by Direct Smelting, tonnes

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EFDS = emission factor for Direct Smelting, tonne CO2/tonne lead product
ISF = quantity of lead produced from the Imperial Smelting Furnace, tonnes
EFISF = emission factor for Imperial Smelting Furnace, tonne CO2/tonne lead productS = quantity of lead produced from secondary materials, tonnes
EFS = emission factor for secondary materials, tonne CO2/tonne lead product
The CO2 emission factors used in Equation 4.32 are shown in Table 4.21.

TIER 2 METHODThe Tier 2 method recognizes that there are substantial differences in carbon dioxide emissions for leadproduction depending on the production methodology and the source of the raw materials, either from secondary
sources such as recycled batteries, or, from primary production from ores. Secondary lead sources may be pretreated to remove impurities resulting in carbon dioxide emissions. Emissions can be calculated using country
specific emission factors based on the use of reducing agents, furnace types and other process materials ofinterest. Factors can be developed based on carbon contents applicable to those materials. Table 4.22 provides
carbon contents that can be used to derive country-specific factors. These data may be available fromgovernmental agencies responsible for manufacturing or energy statistics, business or industry trade associations,or individual lead companies. Tier 2 is more accurate than Tier 1 because it takes into account the materials andthe variety of furnace types used in the lead sector that contribute to CO2 emissions for a particular country
rather than assuming worldwide industry-wide practices.

TIER 3 METHOD
If actual directly measured CO2 emissions data are available from lead facilities, these data can be aggregatedand used directly to account for national emissions using the Tier 3 method. Total national emissions will equal
the sum of emissions reported from each facility. If facility emissions are not available, emissions should be
calculated from plant-specific data for individual reducing agents and other process materials. To achieve ahigher level of accuracy than Tier 2, it is good practice to develop emissions estimates at the plant-level because
plants can differ substantially in their technology, specifically furnace technology. These data may be available
from governmental agencies responsible for manufacturing or energy statistics, or from business or industry
trade associations, but is preferably aggregated from data furnished by individual lead facilities.

4.6.2.2

C HOICE OF EMISSION FACTORSTIER 1 METHOD
When the only data available are national lead production statistics, it is good practice to use default emission
factor of 0.52 tonne of CO2/ tonne of lead (Sjardin 2003). This default should only be used when no information
is available on the relative amounts of lead produced from primary and from secondary materials. If information
is available, emissions should be calculated using the appropriate factors in Table 4.21. (Sjardin, 2003). The
uncertainty in the default factor is high and varies depending on the mix of production methods and thepercentage of secondary processing. In addition, the factor assumes that 80 percent of the world’s leadproduction (including both primary and secondary) is smelted using an Imperial Smelting Furnaces, while theremaining 20 percent is smelted using the direct smelting method in the Kivcet, Ausmelt, and QueneauSchumann-Lurgi furnaces (Sjardin, 2003).
TABLE 4.21
GENERIC CO2 EMISSION FACTORS FOR LEAD PRODUCTION BY SOURCE AND FURNACE TYPE
(tonnes CO2/tonne product)
From Imperial Smelt
Furnace (ISF) Production

From Direct Smelting(DS) Production

From Treatment ofSecondary Raw Materials

Default Emission Factor(80% ISF, 20% DS)

0.59

0.25

0.2

0.52

Source: Sjardin (2003)

TIER 2 METHODThis method offers the opportunity to adjust emission factors to reflect variations from the presumed norms
based on plant-specific data for the carbon content of these materials and based on furnace type. The default
carbon contents in Table 4.22 should be used if an inventory compiler does not have information on conditions

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in lead facilities, but has detailed activity data for the process materials. The default values in Table 4.22 arederived from the default values in Tables 1.2 and 1.3 in Volume 2, Chapter 1 and should be referenced forfurther information.
TABLE 4.22
MATERIAL-SPECIFIC CARBON CONTENT FOR LEAD PRODUCTION (kg carbon/kg )Process Materials

Carbon Content

Blast Furnace Gas

0.17

Charcoal*

0.91

1

0.67

Coal Tar

0.62

Coke

0.83

Coke Oven Gas

0.47

Coal

Coking Coal

0.73
2

EAF Carbon Electrodes

0.82

3

EAF Charge Carbon

0.83

4

0.86

Gas Coke

0.83

Natural Gas

0.73

Petroleum Coke

0.87

Fuel Oil

Source: References for carbon content data are included in Table 1.2 and 1.3 in Volume 2, Chapter 1.
Notes:
1

Assumed other bituminous coal

2

Assumed 80 percent petroleum coke and 20 percent coal tar

3

Assumed coke oven coke

4

Assumed gas/diesel fuel* The amount of CO2 emissions from charcoal can be calculated by using this carbon content value, but it should be reported as zero innational greenhouse gas inventories. (See Section 1.2 of Volume 1.)

TIER 3 METHODThe Tier 3 method is based on aggregated emission estimates or the application of the Tier 2 at a plant-specificlevel. The inventory compiler should ensure that each facility has documented the emission factors and carbon
contents used, and that these emission factors are indicative of the processes and materials used at the facility.
The Tier 3 method requires carbon contents and production/consumption mass rates for all of the processmaterials and off-site transfers such as those listed in Table 4.22. While Table 4.22 provides default carbon
contents, it is good practice under Tier 3 to adjust these values to reflect variations at the plant level from default
values represented in the table. The default factors listed in Table 4.22 are only appropriate for the Tier 3
method if plant-specific information indicates that they correspond to actual conditions. It is anticipated that for
the Tier 3 method the plant-specific data would include both carbon content data and production/consumption
mass rate data, and that therefore the default values in Table 4.22 would not be applied to the Tier 3 method inmost instances.

4.6.2.3

C HOICE OF ACTIVITY DATATIER 1 METHODThe Tier 1 method requires only the amount of lead produced in the country and if available, the amountproduced by furnace type. These data may be available from governmental agencies responsible for
manufacturing statistics, business or industry trade associations, or individual lead companies. These tonnages
can then be multiplied by the corresponding emission factor in Table 4.21 to estimate CO2 emissions from thesector or the default factor if furnace type is unavailable.

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TIER 2 METHODThe Tier 2 method requires only the total amounts of reducing agents and other process materials used for leadproduction in the country. These data may be available from governmental agencies responsible for
manufacturing or energy statistics, business or industry trade associations, or individual lead companies. Theseamounts can then be multiplied by the appropriate carbon contents in Table 4.22 and summed to determine total
CO2 emission from the sector. However, activity data collected at the plant-level is preferred (Tier 3). If this is
not a key category and data for total industry-wide reducing agents and process materials are not available,
emissions can be estimated using the Tier 1 approach.

TIER 3 METHODThe Tier 3 method requires collection, compilation, and aggregation of facility-specific measured emissions or
activity data. If emissions data are not available, the Tier 3 method requires activity data to be collected at theplant level and aggregated for the sector. The amounts of reducing agents and the type of furnace used are moreaccurately determined in this manner. These data may be available from governmental agencies responsible for
manufacturing or energy statistics, or from business or industry trade associations, but are preferably aggregatedfrom data furnished by individual lead facilities. This approach also allows for additional accuracy by allowing
individual companies to provide more accurate plant-specific data and/or to use more relevant emission factors
to reflect carbon contents and furnace types that may differ from the default factors used in the Tier 2 method.

4.6.2.4

C OMPLETENESS

In estimating emissions from this source category, there is a risk of double counting or omission in either the
IPPU or the Energy Sector. As a general guide, all process emissions from lead production should be reported in
the IPPU Sector.

4.6.2.5

D EVELOPING A CONSISTENT TIME SERIESEmissions from lead production should be calculated using the same method for every year in the time series.
Where data are unavailable to support a Tier 3 method for all years in the time series, these gaps should berecalculated according to the guidance provided in Volume 1, Chapter 5, Time Series Consistency and
Recalculation.

4.6.3

Uncertainty assessment

Uncertainty estimates for lead production result predominantly from uncertainties associated with activity data,
and from uncertainty related to the emission factor. Table 4.23 provides an overview of the uncertainties foremission factors and activity data.

4.6.3.1

E MISSION FACTOR UNCERTAINTIESThe default emission factors used in Tier 1 may have an uncertainty of ± 50 percent. Tier 2 carbon contents are
expected to have an uncertainty of ± 15 percent. Tier 3 unit specific emission factors would be expected to bewithin 5 percent if plant-specific carbon content data are available.

4.6.3.2

A CTIVITY DATA UNCERTAINTIESNational production statistics should be available and likely have an uncertainty of ± 10 percent. For Tier 2, thetotal amount of reducing agents and process materials used for lead production would likely be within 10 percent.
Tier 3 requires plant-specific information on production data (about 5 percent uncertainty). In addition, actual
emissions data for tier 3 would be expected to have ± 5 percent uncertainty.

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TABLE 4.23
UNCERTAINTY RANGES
MethodData Source

Tier 1

National Production Data
Default Emission Factor
Emission Factors by Process Type

± 10%
± 50%
± 20%

Tier 2

Amounts and Types of Reducing Agents Used
Process Material Carbon Contents

± 10%
± 15%

Tier 3

Facility-Derived = Process Materials Data
Facility-Specific Measured CO2 Data
Facility-Specific Emission Factors

± 5%
± 5%

4.6.4
4.6.4.1

Uncertainty Range± 5%

Quality Assurance/Quality Control (QA/QC),
Reporting and Documentation
Q UALITY A SSURANCE /Q UALITY C ONTROL (QA/QC)

It is good practice to conduct quality control checks as outlined in Volume 1, Chapter 6, and an expert review ofthe emissions estimates. Additional quality control checks as outlined in Volume 1, Chapter 6, and quality
assurance procedures may also be applicable, particularly if higher tier methods are used to determine emissions
from this source category. Inventories agencies are encouraged to use higher tier QA/QC for key categories as
identified in Volume 1, Chapter 4.
In addition to the guidance in Volume 1, Chapter 6, specific procedures of relevance to this source category are
outlined below.

Review of emission factors
Inventory compilers should compare aggregated national emission factors with the IPCC default factors in orderto determine if the national factor is reasonable relative to the IPCC default. Differences between national factors
and default factors should be explained and documented, particularly if they are representative of different
circumstances.

Site-specific activity data check
For site-specific data, inventory compilers should review inconsistencies between sites to establish whether theyreflect errors, different measurement techniques, or result from real differences in emissions, operational
conditions or technology. For lead production, inventory compilers should compare plant data with other plants.
Inventory compilers should ensure that emission factors and activity data are developed in accordance withinternationally recognised and proven measurement methods. If the measurement practices fail this criterion,
then the use of these emissions or activity data should be carefully evaluated, uncertainty estimates reconsideredand qualifications documented. If there is a high standard of measurement and QA/QC is in place at most sites,
then the uncertainty of the emissions estimates may be revised downwards.

Expert review
Inventory compilers should include key industrial trade organisations associated with lead production in a review
process. This process should begin early in the inventory development process to provide input to thedevelopment and review of methods and data acquisition
Third party reviews are also useful for this source category, particularly related to initial data collection,measurement work, transcription, calculation and documentation.

Activity data check
For all tier levels, inventory compilers should check with Volume 2: Energy to ensure that emissions fromreducing agents and process materials (coal, coke, natural gas, etc.) are not double-counted or omitted.

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Inventory compilers should examine any inconsistency between data from different plants to establish whether
these reflect errors, different measurement techniques or result from real differences in emissions, operational
conditions or technology. This is particularly relevant to the plant-specific estimates of amounts of reducing
agents or reported carbon content of process materials.
Inventory compilers should compare aggregated plant-level estimates to industry totals for process materials
consumption where such trade data are available.

4.6.4.2

R EPORTING AND D OCUMENTATION

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Volume 1, Section 6.11. It is not practical to include all documentation in the national
inventory report. However, the inventory should include summaries of methods used and references to source
data such that the reported emissions estimates are transparent and steps in their calculation may be retraced.

TIER 1 METHOD
Besides reporting of estimated emissions, it is good practice to report the total lead production by process andcorresponding emission factors used.

TIER 2 METHODGood practice is to document the estimated or calculated emissions, all activity data, and corresponding carbon
contents any assumptions or data justifying alternative values. There should be a clear explanation of the linkage
with the Volume 2, Energy, to demonstrate that double counting or missing emissions have not occurred.

TIER 3 METHODGood practice is to document the calculated emissions and source of all data, taking into account the need toprotect the confidentiality of data for specific facilities if the data are business-sensitive or of a proprietary nature.
In addition, inventory compilers should for all tiers, document all information needed to reproduce the estimate,
as well as the QA/QC procedures.

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4.7

ZINC PRODUCTION

4.7.1

Introduction

PRIMARY PRODUCTION PROCESSES
There are three different types of primary zinc production. The first method is a metallurgical process called
electro-thermic distillation. The process is used to combine roasted concentrate and secondary zinc products intoa sinter feed that is burned to remove zinc, halides, cadmium, and other impurities. The resulting zinc oxide-richsinter is combined with metallurgical coke in an electric retort furnace that reduces the zinc oxides and produces
vaporized zinc which is captured in a vacuum condenser. The reduction results in the release of non-energy
carbon dioxide (CO2) emissions. The electro-thermic distillation process is used in the United State and in Japan.
(Sjardin, 2003; European IPPC Bureau, 2001)
The second method of zinc production is a pyrometallurgical process involving the use of an Imperial Smelting
Furnace, which allows for the simultaneous treatment of lead and zinc concentrates. The process results in thesimultaneous production of lead and zinc and the release of non-energy CO2 emissions. The metallurgicalcoke/coal reductant used in this process must be allocated to lead and zinc production in order to perform anemission calculation without double counting. A mass based allocation results in a factor of 0.74 tonnes
coke/tonne zinc. (Sjardin, 2003; European IPPC Bureau, 2001)
The third zinc production method is the electrolytic process, which is a hydrometallurgical technique. In thisprocess, zinc sulphide is calcined, resulting in the production of zinc oxide. The zinc oxide is then leached insulphuric acid and purified to remove iron impurities, copper, and cadmium. The zinc is then drawn out of thesolution using electrolysis. The electrolytic process does not result in non-energy CO2 emissions. (Sjardin 2003;
European IPPC Bureau 2001)

SECONDARY PRODUCTION PROCESSES
There are more than 40 hydrometallurgical and pyrometallurgical technologies that can be used to recover zincmetal from various materials. The preferred method for a given situation depends on the zinc source(contamination level and zinc concentration) and the desired end use for the recovered zinc. The process
frequently consists of zinc concentration (through physical and/or chemical separation), sintering, smelting, andrefining. In some cases, high grade zinc is removed from this process after physical concentration and consumedby other industries, including iron and steel manufacture, brass manufacture, and zinc die-casting, without going
through the rest of the process steps. (Sjardin, 2003)
The sintering, smelting, and refining steps are identical to the steps used in the primary zinc production process,so certain smelting processes are considered emissive, while the sintering and refining steps are considered nonemissive from the perspective of non-energy CO2 emissions. When the concentration step involves the use of acarbon-containing reductant and high temperatures to volatilize or fume zinc from the source materials, theprocess could result in non-energy CO2 emissions. The Waelz Kiln and slag reduction or fuming processes are
two such concentration methods. The Waelz Kiln process, which is used to concentrate zinc in flue dusts,
sludges, slags, and other zinc-containing materials, involves the use of metallurgical coke as a reductant.
However, the reduced zinc is re-oxided during the processes and the metallurgical coke also serves as a heatsource during the process. The slag reduction or fuming process, which is used strictly to concentrate zinc inmolten slags from copper and zinc smelting, involves the use of coal or another carbon source as a reductant.
(Sjardin, 2003; European IPPC Bureau, 2001)

4.7.2

Methodological issues

4.7.2.1

C HOICE OF METHODThe IPCC Guidelines outline several approaches for calculating CO2 emissions from zinc production. The choiceof a good practice method depends on national circumstances as shown in the decision tree in Figure 4.16. The
Tier 3 method may be used if facility-specific measured emissions data are available. Tier 2 method uses country
specific emissions factors for both primary and secondary production processes. The Tier 1 method is very
simple and it may lead to errors due to its reliance on assumptions rather than actual data. The Tier 1 method
calculates emissions from general emission factors applied to a country’s total zinc production and is the least
rigorous method. This method should only be used when zinc production is not a key category.

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TIER 1 METHOD
The simplest estimation method is to multiply default emission factors by zinc product type (Equation 4.33).
When the only data available are national zinc production statistics, it is good practice to use default emission
factors. If material specific data are not available to calculate emissions using the Tier 2 methodology, but theprocess type is known, inventory compilers can calculate emissions using Equation 4.34.
EQUATION 4.33
CO2 EMISSIONS FROM ZINC PRODUCTION (TIER 1)
E CO 2 = Zn • EFdefault

Where:
ECO2 = CO2 emissions from zinc production, tonnes
Zn = quantity of zinc produced, tonnes
EFdefault = default emission factor, tonnes CO2/tonne zinc produced

EQUATION 4.34
CO2 EMISSIONS FROM ZINC PRODUCTION (TIER 1)
E CO 2 = ET • EFET + PM • EFPM + WK • EFWK

Where:
ECO2 = CO2 emissions from zinc production, tonnes
ET= quantity of zinc produced by electro-thermic distillation, tonnes
EFET = emission factor for electro-thermic distillation, tonnes CO2/tonne zinc produced
PM = quantity of zinc produced by pyrometallurgical process (Imperial Smelting Furnace Process) ,tonnesEFPM = emission factor for pyrometallurgical process, tonnes CO2/tonne zinc produced
WK = quantity of zinc produced by Waelz Kiln process, tonnes
EFWK = emission factor for Waelz Kiln process, tonnes CO2/tonne zinc produced

TIER 2 METHOD
Emission can be calculated using country specific emission factor based on aggregated plant statistics on the useof reducing agents, furnace types and other process materials of interest is developed based on default emission
factors applicable to those materials. These data may be available from governmental agencies responsible for
manufacturing or energy statistics, business or industry trade associations, or individual zinc companies. Tier 2 ismore accurate than Tier 1 because it takes into account the materials and the variety of furnace types used in thezinc sector that contribute to CO2 emissions for a particular country rather than assuming industry-wide practices.

TIER 3 METHOD
If actual measured CO2 emissions data are available from zinc facilities, these data can be aggregated and useddirectly to account for national emissions using the Tier 3 method.

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4.7.2.2

C HOICE OF EMISSION FACTORSTIER 1 METHOD
The emission factor for the pyrometallurgaical process (Imperial Smelting Furnace) is an aggregate, weighted
emission factor encompassing both primary and secondary zinc production in Europe (Sjardin, 2003), No data
was available to determine an emission factor for the electro-thermic process. An emission factor based on theamount of coke consumed per tonne of EAF dust consumed in a Waelz Kiln furnace was developed based on thematerials balance provided by Viklund-White (2000), wherein Viklund-White finds that 400 kg of coke areconsumed for every metric tonne of EAF dust consumed.

TABLE 4.24
TIER 1 CO2 EMISSION FACTORS FOR ZINC PRODUCTION
Process

Emission Factor

SourceWaelz Kiln
(tonne of CO2/ tonne zinc)

3.66

Derived from Viklund-White C. (2000) The Use of LCA for the

Pyrometeallurgical (Imperial
Smelting Furnace)(tonne of CO2/ tonne zinc)

0.43

Electro-thermic

Environmental Evaluation of the Recycling of Galvanized
Steel. ISIJ International. Volume 40 No. 3: 292-299.
Sjardin 2003. CO2 Emission Factors for Non-Energy Use in
the Non-Ferrous Metal, Ferroalloys and Inorganics Industry.
Copernicus Institute, Utrecht, The Netherlands. June 2003.

Unknown

Default Factor(tonne of CO2/ tonne zinc)

1.72

default factor is based on weighting of known emission
factors (60% Imperial Smelting, 40% Waelz Kiln)

TIER 2 METHODThe Tier 2 method requires the calculation of a country specific emission factor based on the total amount of
reducing agents and other carbon containing process materials used for zinc production in the country. These
country specific emission factors should be based on aggregated plant statistics on the use of reducing agents,
furnace types and other process materials of interest. An emission factor was developed based on the amount ofmetallurgical coke consumed per tonne of EAF dust consumed: 0.4 tonnes coke/ tonne EAF dust consumed(Viklund-White, 2000). If activity data are available, an emission factor of 1.23 tonnes of EAF dust per tonne ofzinc could be used to calculate emissions. When producing zinc from EAF dust in a Waelz Kiln furnace, thecomplexities of the process suggest that emission factors are more accurate if they are based on the amount of
EAF dust consumed rather than the total zinc produced . This is because the amount of reduction materials(metallurgical coke) consumed is directly dependent upon the amount, and zinc content, of the EAF dust
consumed. Weighing equipment is used in the Waelz Kiln process to control the amount of metallurgical cokeentered into the kiln (Sjardin 2003; European IPPC Bureau 2001).

4.7.2.3

C HOICE OF ACTIVITY DATATIER 1 METHODThe Tier 1 method requires only the amount of zinc produced in the country, and if available, the process type.
These data may be available from governmental agencies responsible for manufacturing statistics, business orindustry trade associations, or individual zinc companies. These tonnages can then be multiplied by the default
emission factors to estimate CO2 emissions.

TIER 2 METHODThe Tier 2 method requires the calculation of a country specific emission factor based on the total amount of
reducing agents and other carbon containing process materials used for zinc production in the country. These
data may be available from governmental agencies responsible for manufacturing or energy statistics, business orindustry trade associations, or individual zinc companies. These country specific emission factors can then be
multiplied by the production amount to determine total CO2 emission from the sector. If this is not a key
category and data for total industry-wide reducing agents and process materials are not available, emissions canbe estimated using the Tier 1.

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TIER 3 METHODThe Tier 3 method requires collection, compilation, and aggregation of facility-specific measured emissions data,
if any. However, activity data collected at the plant-level can also be used, with separate emission factors foreach plant multiplied by plant specific production. If this is not a key category and data for total industry-wide
reducing agents and process materials are not available, emissions can be estimated using the Tier 1.

Figure 4.16

Decision tree for estimation of CO 2 emissions from zinc production
Start

Are plantspecific emissions
or activity data
available?

Yes

Calculate process emissions
using Tier 3 Method.
Box 3: Tier 3NoArenational data
available for processmaterials used in zincproduction?

Yes

Calculate process emissions
using Tier 2 Method.
Box 2: Tier 2

No

Is this a key
category1?

No

Estimate process emissions
using Tier 1 Method.
Box 1: Tier 1

Yes
Collect data for the Tier 3or the Tier 2 method.
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.

4.7.2.4

C OMPLETENESS

In estimating emissions from this source category, there is a risk of double-counting or omission in either the
Industrial Processes or the Energy Sector. It is important to note that the Tier 1 emission factor assumes that theCO2 emissions from the combustion of various fuels used for production of heat in the calcining, sintering,leaching, purification smelting, and refining processes are captured within the CO2 from fossil fuel combustion
emission category. In using the tier 2 or 3 methodologies, double-counting can be avoided. The largest sourceof potential double-counting, emissions from coke production, are calculated in Section 4.2 and reported in the
Energy Sector.

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4.7.2.5

D EVELOPING A CONSISTENT TIME SERIESEmissions from zinc production should be calculated using the same method for every year in the time series.
Where data are unavailable to support a Tier 3 method for all years in the time series, these gaps should berecalculated according to the guidance provided in Volume 1, General Guidance and Reporting.

4.7.3

Uncertainty assessment

Uncertainty estimates for zinc production result predominantly from uncertainties associated with activity data,
and from uncertainty related to the emission factors. Table 4.25 provides an overview of the uncertainties foremission factors and activity data.

4.7.3.1

E MISSION FACTOR UNCERTAINTIESThe default emission factors used in Tier 1 may have an uncertainty of ± 50 percent. Tier 2 country specificemission factors are expected to have an uncertainty of ± 15 percent. Tier 3 unit specific emission factors would
be expected to be within 5 percent if plant-specific carbon content data are available.

4.7.3.2

A CTIVITY DATA UNCERTAINTIESNational production statistics should be available and likely have an uncertainty of ± 10 percent. For Tier 2, thetotal amount of reducing agents and process materials used for lead production would likely be within 10 percent.
Tier 3 actual emissions data would be expected to have ± 5 percent uncertainty.

TABLE 4.25
UNCERTAINTY RANGES
MethodData Source

Tier 1

National Production Data
Default Emission Factors
Process Specific Emission Factors

± 10%
± 50%
± 20%

Tier 2National Reducing Agent & Process Materials Data
Country Specific Emission Factors

± 10%
± 15%

Tier 3

Facility-Derived = Process Materials Data
Facility-Specific Measured CO2 Data
Facility-Specific Emission Factors

± 5%
± 5%
± 5%

4.7.4
4.7.4.1

Uncertainty Range

Quality Assurance/Quality Control (QA/QC),
Reporting and Documentation
Q UALITY A SSURANCE /Q UALITY C ONTROL (QA/QC)

It is good practice to conduct quality control checks as outlined in Volume 1, Chapter 6, and an expert review ofthe emissions estimates. In addition to the guidance in Volume 1, specific procedures of relevance to this source
category are outlined below.

Review of emission factors
Inventory compilers should compare aggregated national emission factors with the IPCC default factor in orderto determine if the national factor is reasonable relative to the IPCC default. Significant differences between
national factors and the default factor should be explained and documented, particularly if they are representativeof different circumstances.

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Site-specific activity data check
For site-specific data, inventory compilers should review inconsistencies between sites to establish whether theyreflect errors, different measurement techniques, or result from real differences in emissions, operational
conditions or technology. For zinc production, inventory compilers should compare plant data with other plants.
Inventory compilers should ensure that emission factors and activity data are developed in accordance withinternationally recognised and proven measurement methods. If the measurement practices fail this criterion,
then the use of these emissions or activity data should be carefully evaluated, uncertainty estimates reconsideredand qualifications documented. If there is a high standard of measurement and QA/QC is in place at most sites,
then the uncertainty of the emissions estimates may be revised downwards.

Expert review
Inventory compilers should include key industrial trade organisations associated with zinc production in a review
process. This process should begin early in the inventory development process to provide input to thedevelopment and review of methods and data acquisition.
Third party reviews are also useful for this source category, particularly related to initial data collection,measurement work, transcription, calculation and documentation.

Activity data check
For all tier levels, inventory compilers should check to ensure that emissions from reducing agents and processmaterials (coal, coke, natural gas, etc.) are not double-counted as energy related emissions or omitted.
Inventory compilers should examine any inconsistency between data from different plants to establish whether
these reflect errors, different measurement techniques or result from real differences in emissions, operational
conditions or technology. This is particularly relevant to the plant-specific estimates of amounts of reducing
agents or reported carbon content of process materials.
Inventory compilers should compare aggregated plant-level estimates to industry totals for process materials
consumption where such trade data are available.

4.7.4.2

R EPORTING AND D OCUMENTATION

It is good practice to document and archive all information required to produce the national emissions inventory
estimates as outlined in Volume 1, Section 6.11. It is not practical to include all documentation in the national
inventory report. However, the inventory should include summaries of methods used and references to source
data such that the reported emissions estimates are transparent and steps in their calculation may be retraced.

TIER 1 METHOD
Besides reporting of estimated emissions, it is good practice to report the total zinc production by process andcorresponding emission factors used.

TIER 2 METHODGood practice is to document the estimated or calculated emissions, all activity data, and corresponding
emission factors and any assumptions or data justifying alternative emission factors.

TIER 3 METHODGood practice is to document the calculated emissions and source of all data, taking into account the need toprotect the confidentiality of data for specific facilities if the data are business-sensitive or of a proprietary nature.
In addition, inventory compilers should for all tiers, document all information needed to reproduce the estimate,
as well as the QA/QC procedures

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References
SECTION 4.2
EEA (2005). EMEP/CORINAIR. Emission Inventory Guidebook – 2005, European Environment Agency,
Technical report No 30. Copenhagen, Denmark, (December 2005). Available from web site see:
http://reports.eea.eu.int/EMEPCORINAIR4/en
European IPPC Bureau (2001). Integrated Pollution Prevention and Control (IPPC) Best Available Techniques
Reference
Documentonthe
Production
of
Iron
and
Steel,
December
2001.
http://eippcb.jrc.es/pages/FActivities.htm
International Iron and Steel Institute (2004). Steel Statistical Yearbook 2004: International Iron and SteelInstitute, COMMITTEE ON ECONOMIC STUDIES, Brussels.
Pipatti, R. (2001). Greenhouse Gas Emissions and Removals in Finland, Report No. 2094, VTT TechnicalResearch Centre of Finland, Espoo, 2001. http://virtual.vtt.fi/inf/pdf/tiedotteet/2001/T2094.pdf
Schoenberger, H. (2000). European Conference on “The Sevilla Process: A Driver for Environmental
Performance in Industry” Stuttgart, 6 and 7 April 2000, BREF on the Production of Iron and Steel conclusion on BAT, Dr. Harald Schoenberger, Regional State Governmental Office Freiburg, April 2000.

SECTION 4.3
FFF (2000). The Norwegian Ferroalloy Producers Research Association, “Emission factors standardized atmeeting”, Oslo 2000.
IPCC (1997). Revised 1996 IPCC Guidelines for National Greenhouse Inventories. Houghton J.T., Meira Filho
L.G., Lim B., Tréanton K., Mamaty I., Bonduki Y., Griggs D.J. Callander B.A. (Eds). Intergovernmental
Panel on Climate Change (IPCC), IPCC/OECD/IEA, Paris, France.
IPCC (2000). Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories.
Penman J., Kruger D., Galbally I., Hiraishi T., Nyenzi B., Emmanuel S., Buendia L., Hoppaus R.,
Martinsen T., Meijer J., Miwa K., Tanabe K. (Eds). Intergovernmental Panel on Climate Change (IPCC),
IPCC/OECD/IEA/IGES, Hayama, Japan.
Lindstad, T. (2004). ‘CO2 Emissions from the Production of Silicon Alloys’, STF80A04019, SINTEF,
Trondheim 2004.
Olsen, S.E., Monsen, B.E. and Lindstad, T. (1998). ‘CO2 Emissions from the Production of Manganese andChrome Alloys in Norway’, Electric Furnace Conference Proceedings Vol. 56, Iron & Steel Society,
Warrendale PA 1998, pp 363-369.
Olsen, S.E. (2004). ‘CO2 Emissions from the Production of Manganese Alloys in Norway’, STF80A04010,
SINTEF, Trondheim 2004.

SECTION 4.4
IAI (2000). International Aluminium Institute, International Aluminium Institute (2000) ‘Life Cycle Assessmentof Aluminium’
IAI (2001). International Aluminium Institute, Perfluorocarbon Emissions Reduction Programme 1990 - 2000,
2001, available at http://www.world-aluminium.org/iai/publications/documents/pfc2000.pdf.
IAI (2005a). International Aluminium Institute, The Aluminium Sector Greenhouse Gas Protocol,
http://www.world-aluminium.org/environment/climate/ghg_protocol.pdf, 2005.
IAI (2005b). International Aluminium Institute, survey on composition of production materials, 2005
(unpublished)
IAI (2005c). International Aluminium Institute, Annual Anode Effect Survey 2003, www.world-aluminium.org,
2005.
U.S. EPA and IAI (2003), U.S. Environmental Protection Agency and International Aluminium Institute,
USEPA/IAI Protocol for Measurement of PFCs from Primary Aluminium Production, EPA 43-R-03-006,
May 2003.

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Chapter 4: Metal Industry Emissions

SECTION 4.5
Bartos, S., Kantamaneni, R., Marks, J. and Laush, C. (2003). “Measured SF6 Emissions from Magnesium Die
Casting Operations,” Magnesium Technology 2003, Proceedings of The Minerals, Metals & Materials
Society (TMS) Conference, March 2003.
Gjestland, H. and Magers, D. (1996). “Practical usage of sulphur hexafluoride for melt protection in themagnesium die casting industry” Proceedings of the 53rd International Magnesium Conference, 1996,
Ube City, Japan
IPCC (2001). Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third
Assessment Report of the Intergovernmental Panel on Climate Change [Houghton, J.T.,Y. Ding, D.J.
Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnson (eds.)]. Cambridge
University Press, Cambridge, United Kingdom and New York, NY, USA, 881pp.
Milbrath, D. (2002). “Development of 3M™ Novec™ 612 Magnesium Protection Fluid as a Substitute for SF6
Over Molten Magnesium,” International Conference on SF6 and the Environment: Emission Reduction
Technologies, November 21-22, 2002, San Diego, CA.
Tranell, G and Engh, T.A. (2004). “Alternatives to SF6 for the Magnesium Processor – A Technical,
Environmental and Economic Assessment”, Proceedings of the 61st Annual International Magnesium
Association Conference, May 2004, New Orleans, LA, USA.

SECTION 4.6
DOE (2002). Mining Industry of the Future: Energy and Environmental Profile of the U.S. Mining Industry.
Prepared by BCS, Inc for the U.S. Department of Energy’s Office of Energy Efficiency and Renewable
Energy, December 2002.
LDA (2002). Technical Notes: Primary Extraction of Lead., Lead Development Association International.
Internet: http://www.ldaint.org/technotes1.htm
Metallurgical Industry (1995). AP 42, Fifth Edition, Volume I, Chapter 12, http://www.epa.gov/ttn/chief/ap42/
ch12/index.html
Sjardin, M. (2003). CO2 Emission Factors for Non-Energy Use in the Non-Ferrous Metal, Ferroalloys andInorganics Industry. Copernicus Institute, Utrecht, The Netherlands, June 2003.

SECTION 4.7
European IPPC Bureau (2001). Integrated Pollution Prevention and Control (IPPC) Best Available Techniques
Reference
DocumentontheNon
Ferrous
MetalsIndustries,
December
2001.
http://eippcb.jrc.es/pages/FActivities.htm
Sjardin, M. (2003). CO2 Emission Factors for Non-Energy Use in the Non-Ferrous Metal, Ferroalloys andInorganics Industry. Copernicus Institute, Utrecht, The Netherlands, June 2003.
Viklund-White C. (2000). The Use of LCA for the Environmental Evaluation of the Recycling of Galvanized
Steel. ISIJ International. Volume 40 No. 3: 292-299.

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