I had thought photosynthesis and respiration where pretty much Oxygen and Carbon neutral per calorie.
If, as the project plans, crops are cultivated within the settlers’ habitat, Do found that they would produce unsafe levels of oxygen that would exceed fire safety thresholds, requiring continuous introduction of nitrogen to reduce the oxygen level.
Says that a closed system of plants grown to provide calories for human will end up with more oxygen.
Where does the imbalance come from? Where does the extra Carbon go?