New electrode materials will produce oxygen instead of CO2.
In the conventional process alumina (Al2O3) - derived from bauxite - is dissolved in molten cryolite, and electrolyzed in a molten salt bath, typically in a cell with carbon electrodes, causing aluminium to be deposited at the cathode, while oxygen reacts with carbon from the anode to produce mostly carbon dioxide. So even if all the needed electricity would come from, say, hydro-power, you would stoichiometrically still get almost 2.5 tons of CO2 per ton of aluminium produced. In real life it is closer to 12 tons/ton.
But Alcoa has been quietly working since 2009 on technology to produce emissions-free metal at its Pittsburgh Technology Center. Now it has set up a joint venture, called Elysis, with Rio Tinto and the government of Quebec. The new Rio Tinto/Alcoa process eliminates the carbon, using proprietary materials for the electrodes instead, so the only by-product is oxygen. The joint venture intends to invest up to 40 million Canadian dollars, which would include funding to support the supply chain for the proprietary anode and cathode materials.
Products using the new technology are not expected to become commercially available until about 2024.