You can't get more organic than by growing the food yourself but unfortunately, most people who live in the city don't have that luxury. Instead, you are forced to pay a premium for quality food. There is, however, a concept called Agricultural Urbanism that may change all that in the future.
Basically, the idea of Agricultural Urbanism is community-based farming on a grand scale. Each urban district will have one of these mega-structures which allows citizens to grow their own crops as well as sell off the surplus to help with their incomes. The building itself will have many terraces dedicated to a variety of vegetables and be built to allow the maximum amount of sunlight to reach the plants.