I vaguely remember the 4 g/L/day but on further inspection, I now realise that we can’t ever reach that efficiency. If we use the 1 g/L/day but human use 1kg/day (they use less in sleep don’t they?) divided by 2⁄3 it would be about 1.5 m3 (still quite big) and we have to account for the actual foot print which would be much higher (2x higher? 3 m3?).
I am tempted to argue that we don’t have to match the CO2 production rate so perfectly since the CO2 should naturally diffuse a bit, but let’s leave some margin of error on our side.
for the total volume, can’t we just continuously filter out the algae to retain the optimal condition while barely increasing total volume? and since we only use it at night, the total volume need would be less. If we automatically drain it to a hidden larger tank or press it straigth to oil in the basement we maybe saving effort here but increasing volume.