ISO 19694-4:2023
(Main)Stationary source emissions — Determination of greenhouse gas emissions in energy-intensive industries — Part 4: Aluminium industry
Stationary source emissions — Determination of greenhouse gas emissions in energy-intensive industries — Part 4: Aluminium industry
This document specifies a harmonized method for calculating the emissions of greenhouse gases from the electrolysis section of primary aluminium smelters and aluminium anode baking plants. This document also specifies key performance indicators for the purpose of benchmarking of aluminium and boundaries.
Emissions de sources fixes — Détermination des émissions de gaz à effet de serre dans les industries énergo-intensives — Partie 4: Industrie de l'aluminium
General Information
Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 19694-4
First edition
2023-03
Stationary source emissions —
Determination of greenhouse gas
emissions in energy-intensive
industries —
Part 4:
Aluminium industry
Emissions de sources fixes — Détermination des émissions de gaz à
effet de serre dans les industries énergo-intensives —
Partie 4: Industrie de l'aluminium
Reference number
ISO 19694-4:2023(E)
© ISO 2023
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ISO 19694-4:2023(E)
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ISO 19694-4:2023(E)
Contents Page
Foreword .iv
Introduction .v
1 S c op e . 1
2 Nor m at i ve r ef er enc e s . 1
3 Terms and definitions . 1
4 S ymbols and abbreviated terms.2
4 .1 A bbr e v i at e d t er m s . 2
4.2 S ymbols and chemical formulae . 2
4.2.1 Symbols. 2
4 .2 .2 C hem ical f or mu l ae . 4
5 C alculation methods — General remarks . 4
5.1 G eneral . 4
5.2 C alculation methods for process GHG emissions from primary aluminium
production . 4
5.3 S ources of greenhouse gases . 5
5.3.1 Electrolysis . 5
5 . 3 . 2 A no de b a k i n g . 6
5.3.3 Aluminium smelting supporting processes . 6
5.3.4 A lumina refining . 6
5.3.5 Sources of PFC . 6
6 M ethods for calculation of process greenhouse gas emissions . 6
6.1 General . 6
6.2 T ier 1 — Method using process specific formulae with technology typical
parameters for carbon dioxide emissions . 7
6.3 T ier 2 — Method using process specific formulae with facility specific parameters
for carbon dioxide emissions . 7
6.4 C alculation of carbon dioxide emissions from prebake processes . 7
6.4.1 G eneral . 7
6.4.2 G reenhouse gas emissions from prebake anode consumption during
electrolysis . . . 7
6.5 B aking furnace greenhouse gas emissions . 8
6.5.1 General . 8
6 . 5 . 2 F uel . 8
6.5.3 Combustion of volatile matter . 9
6.5.4 B aking furnace packing material . 10
6.5.5 C alculation of greenhouse gas emissions from the Søderberg process . 11
7 M ethods for calculation of PFC emissions .12
7.1 G eneral .12
7.2 T ier 1 method for calculating PFC emissions .12
7.3 T ier 2 method for calculating PFC emissions . 13
7.4 Calculation of PFC emissions from aluminium reduction processes .13
7.4.1 Step 1 — Calculation of the emissions of each PFC gas per tonne of
aluminium .13
7.4.2 Step 2 — Calculation of the total kilogram emissions of each PFC gas .15
7.4.3 S tep 3 — Calculation of the total tonnes of carbon dioxide emissions
equivalent to the PFC emissions . 15
7.5 V erification of the GHG calculation . 15
7.5.1 Validation of the CO emission calculation . 15
2
7.5.2 V alidation of the PFC emission calculation . 16
8 K ey performance indicators .16
Bibliography .17
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ISO 19694-4:2023(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
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expressions related to conformity assessment, as well as information about ISO's adherence to
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 1,
Stationary source emissions.
A list of all parts in the ISO 19694 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
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ISO 19694-4:2023(E)
Introduction
This document serves the following purposes:
— to measure, test and quantify GHG emissions from the aluminium industry;
— to assess the level of GHG emissions performance of production processes over time at production
sites;
— to establish and provide reliable, accurate and quality information for reporting and verification
purposes.
This document can be used to measure, report and compare the GHG emissions of an aluminium
production facility. Data for individual facilities, sites or works can be combined to measure, report and
compare GHG emissions for a company, corporation or group.
Direct fuel-based emissions are not included; for calculation of this part of the GHG emissions, see
ISO 19694-1.
This document deals with sector-specific aspects for the determination of greenhouse gas (GHG)
emissions from aluminium production and is based on documents mentioned under tier 3 of
[6]
Section 4.4.2.4 of the 2006 IPCC guidelines .
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INTERNATIONAL STANDARD ISO 19694-4:2023(E)
Stationary source emissions — Determination of
greenhouse gas emissions in energy-intensive industries —
Part 4:
Aluminium industry
1 S cope
This document specifies a harmonized method for calculating the emissions of greenhouse gases from
the electrolysis section of primary aluminium smelters and aluminium anode baking plants. This
document also specifies key performance indicators for the purpose of benchmarking of aluminium
and boundaries.
2 Normat ive references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 19694-1, Stationary source emissions — Determination of greenhouse gas emissions in energy-intensive
industries — Part 1: General aspects
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 19694-1 and the following
apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
aluminium electrolysis
section of an aluminium primary smelter where aluminium is converted from aluminium oxide to
aluminium metal in electrolysis cells
3.2
anode baking plant
production of carbon anodes for use in aluminium prebake electrolysis cells
3.3
PFC gas
gas emitted from aluminium electrolysis (3.1) consisting of CF and C F
4 2 6
3.4
grid specific CO factor
2
CO factor (t CO /MWh) associated with the electricity delivered to a specific aluminium smelter from
2 2
their supplier
Note 1 to entry: The unit for grid specific CO factor is t CO /MWh.
2 2
1
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ISO 19694-4:2023(E)
4 S ymbols and abbreviated terms
4.1 Abbreviated terms
AE Anode effect
CWPB Centre-worked prebake
DAE Direct anode emissions
DEE Direct electrolysis emissions
GHG Green house gas
HSS Horizontal stud Søderberg
IPCC Intergovernmental Panel on Climate Change
PFC Perfluorocarbon
PFPB Point feeder prebake
SWPB Side-worked prebake
TIE Electrolysis electricity consumption
VSS Vertical stud Søderberg
WBCSD World Business Council for Sustainable Development
WRI World Resources Institute
4.2 S ymbols and chemical formulae
4.2.1 Symbols
A Anode effect minutes per cell-day (equals to frequency multiplied by average duration)
EM
A Anode effect overvoltage
EO
A Net anode consumption
NC
A Ash content in baked anodes
sha
A Ash content in pitch, % mass fraction
shp
A Ash content in packing coke, % mass fraction
shpc
B Baked anode production
A
B Baked anode mass
AW
B typical binder content in paste, % mass fraction
C
C Carbon content of baked anodes
BA
C Carbon content of anode butts
Butt
C Current efficiency for aluminium production
E
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ISO 19694-4:2023(E)
C Carbon in skimmed dust from anode from Søderberg cells, tonnes carbon per tonne aluminium
D
C Emissions of cyclohexane soluble matter, kilograms per tonnes aluminium
SM
E
Emissions of tetrafluoromethane, kg CF per year
CF
4
4
E
Emissions of hexafluoroethane, kg C F per year
CF 2 6
26
E
CO emissions, tonnes per year
CO 2
2
E Emission factor of packing coke, tCO /t of packing coke
FPC 2
F CF
26
CF
26
Mass fraction of
CF CF
4 4
G
AW
G
Mass of loaded green anodes, G = B
A
A
A
B
AW
G Green anode mass
AW
G Global warming potential; use latest G data from IPCC
WP WP
H Hydrogen content in green anode
w
H Hydrogen content in pitch, % mass fraction
p
M Total mass of baked anodes
BA
M Total mass of anode butts
Butt
M Total metal production, tonnes aluminium per year
P
N Net anode consumption, tonnes per tonnes aluminium
AC
O Oxidation factor of packing coke (typically 1 for this stream)
FPC
O Overvoltage coefficient for CF
VC 4
P Paste consumption, tonnes per tonnes aluminium
C
P Packing coke consumed per tonnes of baked anode
CC
P Packing coke mass
CW
R
Emission rates of CF , kg per tonne of aluminium produced
CF 4
4
R
Emission rates of C F , kg per tonne of aluminium produced
CF 2 6
26
S Sulfur content in baked anodes
a
S Sulfur content in calcined coke, % mass fraction
c
S Sulfur content in pitch, % mass fraction
p
S Sulfur content in packing coke, % mass fraction
pc
S
Slope coefficient for CF , kg CF per tonne aluminium per anode effect minute per cell day
CF
4 4
4
W Waste tar collected
T
3
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ISO 19694-4:2023(E)
4.2.2 Chemical formulae
Al Aluminium
Al O Aluminium oxide (alumina)
2 3
C Carbon
CF Tetrafluoromethane
4
C F Hexafluoroethane
2 6
CO Carbon monoxide
CO Carbon dioxide
2
NaAlF Sodium aluminium hexafluoride (cryolite)
6
NaF Sodium fluoride
5 Calculation metho ds — General remarks
5.1 General
This document shall be used in conjunction with ISO 19694-1 which contains generic, overall
requirements, definitions and rules applicable to the determination of GHG emissions for all energy-
intensive sectors, provides common methodological issues and specifies the details for applying the
rules. The application of this document to the sector-specific standards ensures accuracy, precision and
reproducibility of the results.
5.2 Calculation metho ds for process GHG emissions from primary aluminium
production
Figure 1 gives sources of process emissions and references to where in the standard calculation
methods are specified.
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ISO 19694-4:2023(E)
Figure 1 — Decision tree for process carbon dioxide and perfluorocarbon emissions from
primary aluminium production
Process CO emissions in state-of-the-art aluminium smelters comprise around 90 % of total direct
2
CO equivalent emissions, with the balance of emissions consisting of CO from fossil fuel combustion
2 2
and PFC emissions. Guidance on CO emissions from fuel combustion is not included in this document.
2
Methodology for calculating CO emissions from the combustion of fuel in anode baking furnaces is
2
[6],[7]
described elsewhere , while methodology for calculating process CO emissions is given in Clause 7.
2
5.3 S ources of greenhouse gases
5.3.1 Electrolysis
Most of the CO emissions result from the electrolytic reaction of the carbon anode with alumina as
2
given in Formula (1):
2AlO +3C→4Al+3CO (1)
23 2
Carbon dioxide is also emitted during the electrolysis reaction as the carbon anode reacts with other
sources of oxygen, primarily from the air. Carbon dioxide is also formed as a result of the Boudouard
reaction where CO reacts with the carbon anode forming carbon monoxide, which is then oxidized to
2
5
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ISO 19694-4:2023(E)
form CO . Each unit of CO participating in the Boudouard reaction produces two units of CO after air
2 2 2
oxidation [see Formulae (2) and (3)]:
CO +C→2CO (2)
2
2CO+O2→ CO (3)
22
All carbon monoxide formed is assumed to be converted to CO . By industry convention, no correction
2
is made for the minute amount of carbon consumed as PFCs rather than CO emissions. No CO is
2 2
produced from cathode consumption unless there is on-site incineration and no recommendation is
included here. For such operations, CO emission from addition of sodium carbonate to electrolyses
2
cells is not included as this is added at infrequent intervals and is an insignificant source.
5.3.2 Anode baking
Another source of CO emissions, specific to prebake technologies, is the baking of green anodes,
2
wherein CO is emitted from the combustion of volatile components from the pitch binder and, for
2
baking furnaces fired with carbon based fuels, from the combustion of the fuel source. Some of the
packing coke used to cover the anodes is also oxidized, releasing CO during anode baking.
2
Carbon dioxide is emitted from the fuel used in the paste plant and the fuel used for firing the anode
baking furnace.
5.3.3 Aluminium smelting supporting processes
A further source of carbon dioxide emissions is fuel used in the cast house for heating of the metal
during treatment processes before casting, and some fuel can also be used in rodding operations.
5.3.4 Alumina refining
Carbon dioxide is not produced as process emission in the Bayer Process, the process through which
alumina is refined from bauxite ore. Most of the emissions associated with alumina refining are from
[10]
the combustion of fossil fuels, which are covered in the WRI/WBCSD calculation tools for GHG
emissions from energy and electricity.
5.3.5 Sources of PFC
Two perfluorocarbon gases (PFCs), tetrafluoromethane (CF ) and hexafluoroethane (C F ), can be
4 2 6
produced during primary aluminium production [see Formulae (4) and (5)].
4NaAlF +3C→+4Al+12NaF 3CF (4)
36 4
4NaAlF +4C→4Al+12NaF+2C F (5)
36 26
NOTE The following recommendations for calculating PFC emissions are consistent with the inventory
[6],[15]
guidance of the Intergovernmental Panel on Climate Change (IPCC) .
6 Methods for calcul ation of process greenhouse gas emissions
6.1 General
Direct CO emissions from aluminium production shall be calculated by using one of the following two
2
tiers:
— tier 1: process specific formulae with industry typical parameters;
6
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ISO 19694-4:2023(E)
— tier 2: process specific formulae with site or company specific parameters.
NOTE Tier 1 and tier 2 in this document correspond to what is listed as tier 2 and tier 3 in the IPCC technical
[6]
guidance .
Reference should be made to Figure 1 as an overall guide on how to proceed when calculating direct
CO emissions. For calculation of key performance indicator, tier 2 shall be used.
2
6.2 Tier 1 — Method using process specific formulae with technology typical
parameters for carbon dioxide emissions
Tier 1 method for the calculation of total direct CO emissions shall be based on the calculation of
2
CO emissions from each individual process step which are then summed to calculate total emissions.
2
Formulae in 6.4 specify the calculation of CO for prebake technologies, while 6.5.5 contains the
2
formulae for Søderberg technologies.
6.3 Tier 2 — Method using process specific formulae with facility specific parameters
for carbon dioxide emissions
The most accurate inventories of CO are obtained by using site or company specific data in the formulae
2
for calculating emissions (tier 2 method). This data can come from measurements made on site or from
data from suppliers. The formulae are identical to those used in the tier 1 method specified above.
However, facility specific or company specific data, rather than technology typical data, shall be used.
6.4 Calculation of car bon dioxide emissions from prebake processes
6.4.1 General
Carbon dioxide emissions resulting from CWPB and SWPB reduction technologies have as their sources
electrolysis and anode baking.
6.4.2 Greenhouse gas emissions from prebake anode consumption during electrolysis
The following formula should be used for calculation of CO emissions from prebake anode consumption
2
during electrolysis:
100−−SA
asha
E= MN× ×3,664 (6)
CO PAC
2
100
where
E is the CO emissions in tonnes per year;
2
CO
2
M is the total metal production, tonnes aluminium per year;
P
N is the net anode consumption, tonnes per tonne aluminium;
AC
S is the sulfur content in baked anodes, % mass fraction;
a
A is the ash content in baked anodes, % mass fraction;
sha
3,664 is the CO molecular mass: carbon atomic mass ratio, t CO /t C.
2 2
Parameters used in Formula (6) are specified in Table 2 together with technology typical values for
calculating CO emissions from prebake anode consumption during electrolysis.
2
7
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ISO 19694-4:2023(E)
Alternatively, the following formula may also be used:
EM=×()CM−×C 3× ,664 (7)
CO BA BA Butt Butt
2
where
E is the CO emissions, tonnes per year;
2
CO
2
M is the total mass of baked anodes, tonnes anodes per year;
BA
C is the carbon content of baked anodes, % mass fraction;
BA
M is the total mass of anode butts, tonnes anodes per year;
Butt
C is the carbon content of anode butts, % mass fraction.
Butt
Parameters used in Formula (7) are defined in Table 1 together with technology typical values for
calculating CO emissions from prebake anode consumption during electrolysis.
2
Table 1 — Typical uncertainty for individual parameters and analyses used in tier 1 or tier 2
method for carbon dioxide emissions from prebake cells
Tier 1 method Tier 2 method
Parameter
Data source Data uncertainty Data source Data uncertainty
±% ±%
M , tonnes aluminium per year Individual facility records 2 Individual facility records 2
P
N , tonnes per tonne aluminium Individual facility records 5 Individual facility records 5
AC
S , % mass fraction Use industry typical value, 2 3 Individual facility records 3
a
A , % mass fraction Use industry typical value, 0,4 3 Individual facility records 3
sha
M , tonnes anodes per year Individual facility records 2 Individual facility records 2
BA
C , % mass fraction Use industry typical value, 98 5 Individual facility records 2
BA
M , tonnes anodes per year Individual facility records 2 Individual facility records 2
Butt
C , % mass fraction Use industry typical value, 98 5 Individual facility records 2
Butt
6.5 Baking furnac e greenhouse gas emissions
6.5.1 General
Baking furnace emissions result from three sources:
— combustion of the fuel for firing the furnace;
— combustion of volatile matter released during the baking operation;
— combustion of baking furnace packing material.
6.5.2 Fuel
Carbon dioxide emissions resulting from the fuel consumed during baking furnace firing can be
[10]
calculated using the WRI/WBCSD calculation tools for GHG emissions from energy and electricity.
8
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ISO 19694-4:2023(E)
6.5.3 Combustion of volatile matter
Calculation of carbon dioxide emissions from pitch volatiles combustion should be calculated according
to:
HG×
WA
EG=− −−BW ×3,664 (8)
CO A AT
2
100
where
E is the CO emissions, tonnes per year;
2
CO
2
G
AW
G
is the mass of loaded green anodes, G = B ;
A
A
A
B
AW
G is the green anode mass, tonnes;
AW
B is the baked anode mass, tonnes;
AW
B is the baked anode production, tonnes baked anode per year;
A
H is the hydrogen content in green anodes, % mass fraction;
W
W is the waste tar collected, tonnes;
T
3,664 is the CO molecular mass: carbon atomic mass ratio, dimensionless.
2
Parameters included in Formula (8) are specified and industry typical values noted in Table 2.
Alternatively, Formula (9) may also be used:
EG= ×− C B ×C ×3,664 (9)
()
CO AW GA AW BA
2
where
is the CO emissions, tonnes per year;
E
2
CO
2
G is the green anodes mass, tonnes;
AW
C is the carbon content of green anodes, % mass fraction;
GA
B is the baked anodes mass, tonnes;
AW
C is the carbon content of baked anodes, % mass fraction.
BA
9
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ISO 19694-4:2023(E)
Table 2 — Typical uncertainty for individual parameters and analyses used in tier 1 or tier 2
method for CO emissions from bake furnace pitch volatiles combustion
2
Tier 1 method Tier 2 method
Parameter
Data source Data uncertainty Data source Data uncertainty
±% ±%
Individual facility
G , in tonnes Individual facility records 2 2
AW
records
Individual facility
B , in tonnes Individual facility records 2 2
AW
records
Individual facility
H , in % mass fraction Use industry typical value, 0,5 5 5
W
records
Individual facility
B , in tonnes per year Individual facility records 2 2
A
records
W , in tonnes
T
Use industry typical value:
a) Riedhammer fur- Individual facility
a) 0,005 × G 20 20
A
naces records
b) Insignificant
b) All other furnaces
Individual facility
C , in % mass fraction Use industry typical
...
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