In order to have a pure output of oxygen and fuel from CO2 and water, don't you need a pure source of CO2 and a very clean source of water? Could you provide s

In order to have a pure output of oxygen and fuel from CO2 and water, don't you need a pure source of CO2 and a very clean source of water? Could you provide some more detail on how these inputs are obtained? How much CO2 are you able to extract over a day? Do the input rates suffer from depleting the accessible CO2 from the local airspace in the same way that plants do?