Growing crops in cities in skyscrapers has been gaining a lot of attention lately in planning circles. Yet the very problem they have been proposed to solve -- energy-intensive and industrial agriculture -- might only be worse with vertical farms because lighting would need to be supplied artificially to most of the lower levels. Cox and Van Tassel write:
"The idea for vertical agriculture grows out of the realization that there are not enough exposed horizontal surfaces available in most urban areas to produce the quantities of food needed to feed urban populations. Although the concept has provided opportunities for architecture students and others to create innovative, sometimes beautiful building designs, it holds little practical potential for providing food.
For obvious reasons, no one has ever proposed stacking solar photovoltaic panels one above the other. For the same reasons, crop fields cannot be layered one above the other without providing a substitute for the sunlight that has been cut off. Even with all-glass walls, the amount of light reaching plants on all but the top story of a high-rise would fall far, far short of what is needed.
Our calculations, based on the efficiency of converting sunlight to plant matter, show that just to meet a year's U.S. wheat production with vertical farming would, for lighting alone, require eight times as much electricity as all U.S. utilities generate in an entire year...The U.S. corn crop would require energy for lighting equivalent to 40 times the current US electricity supply."
Furthermore, they point out that the resources required to build such structures and move the necessary water and soil, as well as to maintain environmental conditions, would far outweigh any gain. The only answer, according to the authors, is to scale back our industrial agricultural practices and grow more diverse and climatically appropriate crops.