1. Vertical farming is a cool concept, but sadly it won't work, because you need way too much energy to provide enough light (link)
2. Hydroponics is nice, but it may be a bit costly when it comes to building your custom installation
3. The idea: mass produce hydroponic sachets, in transparent,
biodegradable, bioplastic bags.
-the bags contain (1) a bit of earth, (2) a seed, (3) a sachet of water, (4) a sachet of a nutrient rich solution (3 and 4 can be combined, but for style we keep them apart).
-the nutrient and water sachets are like a baxter; they contain a precise dose for a particular crop
-even though water and nutrients are distributed very precisely, any excess is recycled, via a capillary tube
-you can hang these hydroponic bags in front of any window and your plant will begin to grow
-this allows for 'vertical' farming in skyscrapers
-this can be mass produced, and distributed according to any customer's needs (you can tear off your preferred amount of sachets from a big roll)
-the transparency of the bags makes it so that light still enters the office / building's / skyscraper's spaces; the liquids in the sachets are translucent too
-the biodegradability of the bags makes it so that you can throw them away along with the earth after harvesting your food; or if you have a special green collection / recycling service it will gladly accept the waste sachets to make organic fertiliser out of them
-thus you could massively produce food in the megacities, without requiring new land!!
-lettuce, small tomatos, spinach... I can see them hanging all over town!!
I made a drawing of the idea (link).