Carbon electrodes are cheap in some ways, but in making aluminum, they're consumed. They're part of the Hall-Heroult electrochemical reaction. For every three kilos of aluminum produced, two kilos of carbon are oxidized to CO2. The Elysis process sounds good, but the absence of CO2 byproduct comes at an energy cost. The electrolysis cell voltage will be something like 50% higher. If the electricity is from low carbon sources, then the new process is good for the environment. It's probably good for the producer's bottom line also, as the cost of making consumable carbon electrodes is almost certainly greater than the cost of the electricity their use saves. But it is a tradeoff that has to be weighted.