Understanding CBAM for Aluminium Products

The aluminium sector presents unique challenges for CBAM calculations due to its significant electricity consumption and the potential generation of perfluorocarbons (PFCs) during production. As one of the most electricity-intensive industrial processes, primary aluminium production’s carbon footprint varies dramatically based on the power source used.

Production Routes and Emissions Sources

Aluminium production emissions come from two main routes:

• Primary production (electrolysis): Converting alumina to aluminium through the Hall-Héroult process
• Secondary production: Recycling aluminium scrap through remelting

Key emission sources include:

1. Direct CO2 from anode consumption
2. PFC emissions from ‘anode effects’ during electrolysis
3. Indirect emissions from electricity consumption
4. Process emissions from auxiliary processes

Special Consideration: PFC Emissions

PFCs (CF4 and C2F6) are particularly potent greenhouse gases:

• CF₄ has a Global Warming Potential (GWP) of 6,630
• C₂F₆ has a GWP of 11,100 These must be carefully accounted for in CBAM calculations.

Mathematical Basis

The total embedded emissions calculation follows this formula:

For Primary Aluminium:

Total Emissions = Direct CO2 + PFC Emissions + Indirect Emissions

Where:

Direct CO2 = (Anode Consumption × 3.00) + (Process Emissions × 1)

PFC Emissions = (AEM × (SEFCF4/1000) × PrAl × GWPCF4) + 
                (CF4 Emissions × FC2F6 × GWPC2F6)
Where:
- AEM = Anode Effect Minutes per cell-day
- SEFCF4 = Slope Emission Factor for CF4
- PrAl = Aluminium Production in tonnes
- FC2F6 = Weight fraction of C2F6 to CF4
- GWP values as per IPCC AR5

Indirect Emissions = Electricity Consumption × Grid Factor
Where:
- Electricity consumption ≈ 13-15 MWh/tonne aluminium
- Grid Factor varies by country

For Secondary Aluminium:

Total Emissions = (Scrap × 0.02) + (Energy Consumption × Emission Factor) +
                 (Process Materials × Material Factors)

Where:
- Scrap factor (0.02) represents preprocessing emissions
- Energy consumption typically 0.5-1.5 MWh/tonne
- Process materials include salts and inert gases

Data sources:

• PFC emission factors: 2019 Refinement to IPCC Guidelines
• Electricity consumption: International Aluminium Institute data
• Grid intensity: IEA country-specific data
• Process emissions: EU ETS benchmarking data
• GWP values: IPCC Fifth Assessment Report