- Humans need food to live because it provides energy and nutrients.
- From a fundamental standpoint of physics and available materials, nutrients are relatively easy to get; as far as I know, most vitamins and minerals are pretty cheap to either come by naturally or manufacture, and you don't need that much of any of them to keep a person healthy, so let's assume food energy is the real limiting factor here.
- The energy in most food comes from photosynthesis (either directly, in the case of eating plants, or indirectly, in the case of feeding plants to animals for growing meat).
- Photosynthesis is an extremely inefficient way to turn solar radiation into chemical energy. Only about 3 to 6 percent of incoming solar energy is used by plants to create biomass, and not all of that biomass necessarily equates to calories we can digest and absorb.
So, while this isn't a particularly appetizing future to imagine living in, I don't know of any fundamental reason why artificially producing edible calories via solar electricity and chemical processes couldn't vastly exceed the efficiency of natural-grown food. It might be tricky getting to the point where fake food like this is healthy and tastes good...but if it saves the world from starving and stops civilization from collapsing then hey, it's not a bad fallback plan.
Besides being a big jump in efficiency, this type of tech could also enable the use of non-arable land for food production, since presumably you could set up the necessary manufacturing facilities anywhere you want.