Tiger Blood said:
But what about carbohydrate since that is also part of photosynthesis? I mean would it be edible? What taste it would have? Would it be more like a potato or apple or banana or something else?
The carbohydrate doesn't have to be edible to human beings to be useful.
1) It could be combustible fuel, so that the carbon is recycled..
a) One may be able to use it for gasoline, heat or electricity.
2) It could be a source of organic materials.
a) For chemicals, plastic, asphalt-substitutes, wood-substitutes, medicine or other places where now we use petroleum.
3) It could be food for heterotrophic organisms like animals, protozoa, fungi or bacteria.
a) The heterotrophic organisms could be food, fuel or chemicals.
The argument for nonbiological photosynthesis is that it may be faster and more efficient that biological photosynthesis. Plants aren't very efficient with regards to energy. Biological photosynthesis is very far from being a reversible heat engine. Hypothetically, an artificial "tree" can be built that stores almost all the energy incident as sunlight in carbohydrates. However, there are many obvious drawbacks as well as a few we can't imagine just yet.
I am not for this direction of technology. There will be probably be many drawbacks to nonbiological photosynthesis, even if we can make it more efficient in terms of energy. However, in case of ecological disaster there is still another use the carbohydrates.
3b) Copious amounts of liquor for everybody!