An ambitious, almost fantastical, manifestation of agricultural technology is expected to come to fruition this fall. From the remains of an abandoned steel mill in Newark, New Jersey, the creators of AeroFarms are building what they say will be the largest vertical farm, producing two million pounds of leafy greens a year. Whether it even qualifies as a “farm” is a matter of taste. The greens will be manufactured using a technology called aeroponics, a…