How does an aluminium smelter at Richards Bay count PFC emissions for CBAM?

Question

Senseible · Accepted Answer

Record anode effect frequency and duration, or overvoltage, for every potline, convert them to CF4 and C2F6 with plant-specific or default slope coefficients, and multiply by the GWPs set in the CBAM rules. PFCs are direct emissions of unwrought aluminium and count in the CBAM figure. When alumina in the bath runs low, the cell voltage jumps in an anode effect and the carbon anode reacts with the fluoride bath to form CF4 and smaller amounts of C2F6. Both are very potent greenhouse gases, so a few minutes of anode effects per cell-day can add materially to the metal's direct emissions. Log anode effect minutes per cell-day, or overvoltage, per potline from the process control system. Apply the slope or overvoltage coefficients for your cell technology; plant-specific coefficients from measurement campaigns beat defaults. Multiply CF4 and C2F6 by their GWPs from the CBAM rules and add to anode CO2 and on-site fuel. Electricity from the grid is indirect and not charged for aluminium today, even though for coal-heavy grids it is most of the footprint. A carbon tax effectively paid on direct emissions can be claimed under Article 9.

How does an aluminium smelter at Richards Bay count PFC emissions for CBAM?

Where PFCs come from

The method

What does not count

What Senseible does here