PGE makes urban agriculture the promising modern agriculture

Due to the emergence of green propert gravitational energy PGE, urban agriculture has become the promising modern agriculture. Cities have ready-made water supply and drainage systems, even skyscrapers can be used as agricultural factories (reference: the News "Pure green gravitational energy supplies agriculture factory with abundant artificial sunlight", "PGE is the only possibility to resolve population, habitat and food conflicts on Earth" and "PGE seawater desalination and PGE ice/snow melt become two cheap water sources"). Therefore, urban agriculture is more convenient and effective than building rural cities and then developing urban agricultural factories.