Perfluorocarbons (PFCs) can be produced in the primary aluminium reduction process, during events referred to as anode effects. An anode effect is a process upset condition, where an insufficient amount of alumina is dissolved in the electrolyte bath. This causes the voltage in the pot to be elevated above the normal operating range, resulting in the emission of gases containing the PFCs tetrafluoromethane (CF4) and hexafluoroethane (C2F6).
The data presented here is not suitable for life cycle assessment (LCA) purposes, rather data from the IAI life cycle inventory (LCI) report (http://www.world-aluminium.org/media/filer_public/2013/09/05/2010_life_cycle_inventory_report.pdf) or from alternative sources, such as regional aluminium associations or life cycle data providers, should be used.
Source of Data
The data included in this IAI Statistical Report have been developed according to methodologies described in the IAI’s annual Anode Effect Survey Report, based on reported data (http://www.world-aluminium.org/publications/tagged/PFC/).
The IAI Statistical System is designed to meet the requirement that, in general, individual company data be included only within appropriately aggregated totals and not be reported separately. PFC Emissions are aggregated by different technologies as follows:
- CWPB: Centre Worked Prebake – Bar broken centre feed
- PFPB: Centre Worked Prebake – Point centre feed
- SWPB: Side Worked Prebake
- HSS: Horizontal Stud Soderberg
- VSS: Vertical Stud Soderberg
Past IAI reports have used the recommended UNFCCC GWPs which are based on Climate Change 1995, The Science of Climate Change: Summary for Policymakers and Technical Summary of the Working Group I Report, page 22. (see reference https://unfccc.int/ghg_data/items/3825.php) and these values are still the recommended values for parties to the Convention to report GHG emissions data. The GWP values (7390 for CF4 and 12,200 for C2F6) contained in IPCC AR4 issue apply to IAI annual publication till 2019.
From 2021, PFC data is published biennially, inclusive of both – high voltage (HV) PFC emissions and low voltage (LV) PFC emissions by following the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories (https://www.ipcc.ch/report/2019-refinement-to-the-2006-ipcc-guidelines-for-national-greenhouse-gas-inventories/). GWP values updated in IPCC AR5 are adopted, ie. 6630 for CF4 and 11,100 for C2F6
The IAI considers the figures shown to be reliable, but they may be subject to revision. One asterisk * indicates that the number is revised from previous publication.