I think... you might want to read up on aluminum smelting, which converts alumina (Al2O3) into aluminum (Al). The process involves passing a large current between two graphite (carbon) electrodes via the alumina.

Al2O3 + carbon => Al + CO2

Edit: I can only guess that the down votes are for not providing a source? Here you go:

http://en.wikipedia.org/wiki/Aluminium_smelting

It doesn't matter if the smelter runs on fairy dust or hippie juice. Reducing aluminum oxide to aluminum produces CO2 no matter the energy source.