Video: Nick Blumberg for “Chicago Tonight”

A once-vacant lot in West Humboldt Parkhas been transformed into a year-round farm that uses an innovative growing method to raise fresh fish and greens.

Inside the 12,000-square-foot greenhouse that isMetropolitan Farmsare roughly 3,000 fish swimming in six 800-gallon tanks. There are also rows and rows ofleafy greens and herbs, like basil, kale, Swiss chard and a proprietary salad mix.

The method in place is called aquaponics. It combines aquaculture – the breeding and harvesting of fish – and hydroponics – the growing of plants in water. It's also free of synthetic fertilizers and pesticides.

Benjamin Kant, the 30-year-old CEO and founder of the farmcalls it a “superior growing methodbecause of how natural it is.” The farm is projected to grow 92,000 heads of lettuce and 5,600 pounds of fish in its first year.

In aquaponics, the waste produced by fish is converted into plant nutrients like nitrogen by bacteria in the water. When the plants extract these nutrients from the water they purify it; the clean water is then sent back into the fish tanks.

“The bacteria are essentially the engine of the system,” Kant said. “They take the fuel – the fish waste – and turn it into nutrients.”

Kant developed the idea while earning his master’s of business administration at University of Illinois at Chicago.

“We have a long winter and we don’t have a lot of fresh food that’s produced during that time,” Kant said. “If we can grow the fresh food for Chicago while the local farmers can’t do it, then we’re really satisfying a need in the city.”