Why do the anodes used in the electrolytic cell for the reduction of alumina need to be replaced regularly?

Why do the anodes used in the electrolytic cell for the reduction of a

1.	Why do the anodes used in the electrolytic cell for the reduction of alumina need to be replaced regularly?
Answer» The oxygen liberated at the anode during the reduction of alumina, reacts with the carbon of the anode to form CO and CO burns away the anode and hence the anodes need to be replaced.