Life cycle assessment of primary aluminum production in North America using inert anodes

Aluminum is an essential material whose demand across various industries is expected to increase. Inert anodes have long been proposed as alternatives to carbon anodes during the smelting process as a means of reducing emissions and anode material consumption. However, the net energy and emissions tradeoff when accounting for inert anode manufacturing and smelting with an inert anode remain unclear. This work contributes the first life cycle assessment (LCA) of primary aluminum production in North America while modeling inert anodes in the smelter. Reductions in electrolysis emissions and anode replacement rates were modeled using values from literature. To account for other uncertainties, 90 scenarios varying the smelter’s electricity grid mix, smelting energy magnitude, and inert anode production impact were modeled. The LCA results show that for a representative North American smelter using inert anodes produced with the same impact as producing carbon anodes, a smelting energy below 61 MJ/kg aluminum yields some reduction in total energy use, depending on the smelting energy, and at least a 37% reduction in CO 2 -equivalent (CO 2 eq) emissions. If inert anode production has 10x the impact of carbon anode production, then the maximum allowable smelting energy drops to 57 MJ/kg aluminum instead. Finally, if inert anode production has 25x the impact of carbon anode production, then the maximum allowable smelting energy falls beneath the current North American average of 50 MJ/kg aluminum.