Saying net production of oxygen is zero is not identical to saying net sequestration of carbon dioxide is zero. Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 Yo

Saying net production of oxygen is zero is not identical to saying net sequestration of carbon dioxide is zero. Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 You can see here that there's glucose (a carbohydrate) being produced in addition to oxygen.