The operator shall apply the following for emissions of perfluorocarbons (PFCs) resulting from anode effects including fugitive emissions of PFCs. For associated CO2 emissions, including emissions from electrode production, the operator shall apply section 7 of this Annex.
PFC emissions shall be calculated from the emissions measurable in a duct or stack (‘point source emissions’) as well as fugitive emissions using the collection efficiency of the duct:
PFC emissions (total) = PFC emissions (duct)/collection efficiency
The collection efficiency shall be measured when the installation-specific emission factors are determined. For its determination the most recent version of the guidance mentioned under Tier 3 of section 4.4.2.4 of the 2006 IPCC Guidelines shall be used.
The operator shall calculate emissions of CF4 and C2F6 emitted through a duct or stack using one of the following methods:
Method A where the anode effect minutes per cell-day are recorded;
Method B where the anode effect overvoltage is recorded.
The operator shall use the following equations for determining PFC emissions:
CF4 emissions [t] = AEM × (SEFCF4/1 000) × PrAl
C2F6 emissions [t] = CF4 emissions * FC2F6
Where:
=
Anode effect minutes/cell-day;
=
Slope emission factor [(kg CF4/t Al produced)/(anode effect minutes/cell-day)]. Where different cell-types are used, different SEF may be applied as appropriate;
=
Annual production of primary Aluminium [t];
=
Weight fraction of C2F6 (t C2F6/t CF4).
The anode effect minutes per cell-day shall express the frequency of anode effects (number anode effects/cell-day) multiplied by the average duration of anode effects (anode effect minutes/occurrence):
AEM = frequency × average duration
:
The emission factor for CF4 (slope emission factor, SEFCF4) expresses the amount [kg] of CF4 emitted per tonne of aluminium produced per anode effect minute/cell-day. The emission factor (weight fraction FC2F6) of C2F6 expresses the amount [t] of C2F6 emitted proportionate to the amount [t] of CF4 emitted.
:
The operator shall use technology-specific emission factors from Table 1 of this section of Annex IV.
:
The operator shall use installation-specific emission factors for CF4 and C2F6 established through continuous or intermittent field measurements. For the determination of those emission factors the operator shall use the most recent version of the guidance mentioned under tier 3 of section 4.4.2.4 of the 2006 IPCC Guidelines(1). The operator shall determine each emission factor with a maximum uncertainty of ± 15 %.
The operator shall determine the emission factors at least every three years or earlier where necessary due to relevant changes at the installation. Relevant changes shall include a change in the distribution of anode effect duration, or a change in the control algorithm affecting the mix of the types of anode effects or the nature of the anode effect termination routine.
| Technology | Emission factor for CF4 (SEFCF4)[(kg CF4/t Al)/(AE-Mins/cell-day)] | Emission factor for C2F6 (FC2F6)[t C2F6/t CF4] |
|---|---|---|
| Centre Worked Prebake (CWPB) | 0,143 | 0,121 |
| Vertical Stud Søderberg (VSS) | 0,092 | 0,053 |
Where the anode effect overvoltage is measured, the operator shall use the following equations for the determination of PFC emissions:
CF4 emissions [t] = OVC × (AEO/CE) × PrAl × 0,001
C2F6 emissions [t] = CF4 emissions × FC2F6
Where:
=
Overvoltage coefficient (‘emission factor’) expressed as kg CF4 per tonne of aluminium produced per mV overvoltage;
=
Anode effect overvoltage per cell [mV] determined as the integral of (time × voltage above the target voltage) divided by the time (duration) of data collection;
=
Average current efficiency of aluminium production [%];
=
Annual production of primary Aluminium [t];
=
Weight fraction of C2F6 (t C2F6/t CF4);
The term AEO/CE (Anode effect overvoltage/current efficiency) expresses the time-integrated average anode effect overvoltage [mV overvoltage] per average current efficiency [%].
:
The emission factor for CF4 (‘overvoltage coefficient’ OVC) shall express the amount [kg] of CF4 emitted per tonne of aluminium produced per millivolt overvoltage [mV]. The emission factor of C2F6 (weight fraction FC2F6) shall express the amount [t] of C2F6 emitted proportionate to the amount [t] of CF4 emitted.
:
The operator shall apply technology-specific emission factors from Table 2 of this section of Annex IV.
:
The operator shall use installation-specific emission factors for CF4 [(kg CF4/t Al)/(mV)] and C2F6 [t C2F6/t CF4] established through continuous or intermittent field measurements. For the determination of those emission factors, the operator shall use the most recent version of the guidance mentioned under tier 3 of section 4.4.2.4 of the 2006 IPCC Guidelines. The operator shall determine the emission factors with a maximum uncertainty of ± 15 % each.
The operator shall determine the emission factors at least every three years or earlier where necessary due to relevant changes at the installation. Relevant changes shall include a change in the distribution of anode effect duration or a change in the control algorithm affecting the mix of the types of anode effects or the nature of the anode effect termination routine.
| Technology | Emission factor for CF4[(kg CF4/t Al)/mV] | Emission factor for C2F6[t C2F6/t CF4] |
|---|---|---|
| Centre Worked Prebake (CWPB) | 1,16 | 0,121 |
| Vertical Stud Søderberg (VSS) | N.A. | 0,053 |
The operator shall calculate CO2(e) emissions from CF4 and C2F6 emissions as follows, using the global warming potentials listed in Annex VI, section 3, Table 6:
PFC emissions [t CO2(e)] = CF4 emissions [t] * GWPCF4 + C2F6 emissions [t] * GWPC2F6
International Aluminium Institute; The Aluminium Sector Greenhouse Gas Protocol; October 2006; US Environmental Protection Agency and International Aluminium Institute; Protocol for Measurement of Tetrafluoromethane (CF4) and Hexafluoroethane (C2F6) Emissions from Primary Aluminum Production; April 2008.