You are assuming a single-story building growing only one level of crops per floor. It should be feasible to have 2-3 crops for each floor, which cuts down the

You are assuming a single-story building growing only one level of crops per floor. It should be feasible to have 2-3 crops for each floor, which cuts down the required space. For example, the Tesla gigafactory has 229 acres of floor space, and it is high enough for two floors with 2 levels of crops per floor, so 629 would have to be built. The factories could be built in desert areas. Also, the world would be very interesting if 17.4 million acres of land were returned to nature.