In lactic acid fermentation, CO2 is not released, as there is no step of decarboxylation unlike alcohol fermentation. The alcohol fermentation includes the decarboxylation of pyruvic acid to Acetaldehyde, which is further reduced to ethanol due to the reducing agent NADH (which gets oxidized to NAD+. Aerobic respiration (amphibolic pathway) releases CO2 due to oxidative decarboxylation of pyruvic acid to Acetyl-CoA.