Hogland’s solution. The work was done at NASA Ames years ago.
Possible. But why not remove plants completely?
The common thread in all of this is energy. Energy will allow you to decouple from natural conversion processes which are inefficient.
Science and humans can always improve on natural processes... if we understand them. Improve means more efficient with limited resources.
Hoagland’s solution, developed in 1938, improved in 1950 used to great effect by NASA Ames in the 90’s.
From Wiki:
Procedure:
Make up stock solutions and store in separate bottles with appropriate label.
Add each component to 800 mL deionized water then fill to 1 L.
After the solution is mixed, it is ready to water plants.
What many people may not know is that the Hoagland/Arnon nutrient solution formulations require one gallon of nutrient solution to be used per plant with replacement on a weekly basis.
If any of these use parameters are changed, i.e., the volume of solution, number of plants, and/or frequency of replacement, plant performance will be significantly affected, this is a factor that may not be realized by people using the formulations.
But this is not what NASA is asking for, it seems to me. Take a gas and combine it with something common or process it in a simple energy efficient way to create a sugar.
Using plants requires a host of other materials and machinery ... while the end result may be a sugar, the process to too laborious and fragile, not to mention expensive and time consuming, to be viable.