Fast Company staff writer Adele Peters takes a closer look at the roof of a new factory ​ ​ on Chicago's south side, which currently houses a rooftop farm capable of producing over 1 million pounds of leafy greens and herbs per year. Spanning 75,000 square feet, the greenhouse is currently the largest urban farm of its kind.

While Gotham Greens' plant isn't the first rooftop greenhouse​ in the area, it is one of the first to use natural light in lieu of thousands of LEDs, which the company believe isn't ideal for plants and makes the farm more energy efficient. 

"We got into this business to try to address a lot of the global environmental concerns surrounding conventional agriculture," says co-founder Viraj Puri. The greenhouse can't replace everything grown outside—don't expect oranges or wheat anytime soon—but Puri believes that a network of urban farms could eventually replace a large portion of highly perishable foods, like lettuce, that usually travel across the country.

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