What is the role of the graphite rod in the electrometallurgy of aluminium?

(N/A) In the electrometallurgy of aluminium,a fused mixture of purified alumina $(Al_2O_3)$,cryolite $(Na_3AlF_6)$,and fluorspar $(CaF_2)$ is electrolysed. In this process,graphite rods are used as the anode. During electrolysis,$Al$ is liberated at the cathode,while $CO$ and $CO_2$ are produced at the anode due to the reaction of oxygen with the graphite anode.
Cathode: $Al^{3+}_{(melt)} + 3e^- \to Al_{(l)}$
Anode: $C_{(s)} + 2O^{2-}_{(melt)} \to CO_{2(g)} + 4e^-$
If a metal were used as the anode,$O_2$ would be liberated,which would oxidize the metal electrode and convert the produced $Al$ back into $Al_2O_3$. Thus,the graphite anode prevents the formation of $O_2$ and is also cost-effective.