2.C.3 - Aluminium Production

Within category 2.C.3 - Aluminium production, emissions from primary aluminium and secondary aluminium production are reported.

In Germany, primary aluminium is produced in electrolytic furnaces with pre-baked anodes. The pre-baked anodes are produced in separate anode production plants, where petroleum coke and tar pitch are mixed together and subsequently baked. This process produces PAH emissions.

Secondary aluminium is produced in several different furnace types. Emissions can vary according to different scrap qualities. The use of hexachloroethane for degassing during refining operations of secondary aluminium production has been prohibited by law in Germany since 2002, resulting in an omission of the source for HCB.

In 2022 the primary and secondary aluminium production amounted to 814 kt.

The production figures of each year were taken from the annual statistical report of the German association for non-ferrous metals ^{[Lit. 1]}.

The total quantity of waste gas incurred per tonne of aluminium during the production of primary aluminium was multiplied by an average concentration value formed from several individual figures coming from different plants. The values are weighted appropiately and then used to derive the average concentration value.

The emission factors are either default values according to the 2023 EMEP/EEA air pollutant emission inventory guidebook ^{[Lit. 2]} or determined in research projects ^{[Lit. 3]}. The emission factors also make allowance for fugitive emission sources, such as emissions via hall roofs.

The emission factors for SO₂ are calculated from the specific anode consumption. The anodes consist of petrol coke. This material has a specific sulphur concentration of about 1.2 %, from which an SO₂ emission factor of 10.4 kg/t Al can be calculated. The average anode consumption is 430 kg of petrol coke per tonne of aluminium.

The following tables show some process-related emission factors.

Table 1: Emission factors applied for anode production

Benzo(a)pyrene is the lead substance for measurements.

Table 2: Emission factors applied for primary aluminium production

Nitrogen oxide emissions essentially arise from the nitrogen content of the fuels in combustion processes. At temperatures above 1,000 ° C, Nitrogen oxide can also form from nitrogen in the air. Another source of NO_x is the electrolysis in primary aluminium production due to the presence of nitrogen in the anode, which can be oxidized to NO_x. All these emission sources resulting from energy-related processes are included in 1.A.2.b. It is not known whether other sources of NO_x have quantitative effects. In order not to miss process-related NO_x emissions, the standard emission factor is also used. Germany is following recommendations provided by the Expert Review Team for the NECD Review 2017.

The emission factor for CO is adjusted to typical operating parameters mentioned in the technical guideline VDI 2286 “Emission control - Electrolytic aluminium reduction process” ^{[Lit. 4]} in this submission. With that adjustment the emission factor will be harmonized with the standard emission factor of the emission guidebook 2023 lowering the CO emissions.

Table 3: Emission factors applied for secondary aluminium (resmelted aluminium) production

For the period between 1990 and 2001, however, no data on national emissions of HCB in secondary aluminium industries is available. In order to be able to calculate these HCB emissions, the default emission factor for HCB was used.

The uncertainties for the production amounts are 5% and for the emission factors not more than 200%.

Due to the adjustment of the CO-emission factor all CO emissions of primary aluminium production were declined about 33% backwards to 1995.

The activity rates in the NFR-tables erroneously include an additional source. This error could not be corrected before the next submission 2025. As only data for BaP is available the use of default emission factors will be proofed for next submission 2025 to complete PAH emission reporting. This was a recommendation of a NEC-review.

Lit. 1: German association for non-ferrous metals (WirtschaftsVereinigung Metalle): Annual statistical report: https://www.wvmetalle.de
Lit. 2: EMEP/EEA, 2023: EMEP/EEA air pollutant emission inventory guidebook 2023, Copenhagen, 2023. https://www.eea.europa.eu/
Lit. 3: Ökopol, IER, IZT, IfG: Bereitstellung einer qualitätsgesicherten Datengrundlage für die Emissionsberichterstattung zur Umsetzung von internationalen Luftreinhalte- und Klimaschutzvereinbarungen für ausgewählte Industriebranchen Teilvorhaben 2: NE-Metallindustrie, Kalkindustrie, Gießereien.
Lit. 4: VDI 2286 Blatt 1:2013-08 Emissionsminderung Aluminiumschmelzflusselektrolyse (Emission control; Electrolytic aluminium reduction process). Berlin: Beuth Verlag