By Grace Wade and Lauren Bell –
It is an unassuming brick building located in the Back of the Yards, a South Side neighborhood that once housed the Union Stockyards. But a massive mural of gardeners, produce and farm animals painted on the side of the brick building hints at something more than an abandoned meat processing factory. Instead, The Plant turned the factory into a beehive of 25 businesses, including a brewery, a bakery, a coffee roaster and others, committed to the concept of circular economies.
“In a circular economy, waste from one business is reimagined into another product for another business,” said Stephanie Funk as she stood in a room filled with lush plants floating in shallow beds of water under pink and white LED lights. This was The Plant’s aquaponics farm, a productive urban farm and very visual example of a circular economy. Funk, the education associate for Plant Chicago, a nonprofit that coordinates business collaboration at The Plant, notes that most of our society currently operates in a linear economy. Businesses extract resources that are produced into goods that are then consumed by buyers before being trashed. However, circular economies act as an alternative.
The key mechanism behind the aquaponics operation is the nitrogen cycle that provides a source of food for both the 30-35 tilapia housed in large tanks as well as the variety of plants in the growing beds, such as mint and lettuce that use water piped from the tanks. The fish release ammonia both in their waste and through their gills. Then a bacteria called Nitrosomonas breaks down the otherwise toxic ammonia into nitrites. From there another bacteria – Nitrobacter – turns those nitrites into nitrates which can now be used as a fertilizer by the plants.
These nitrates flow in the water from the tanks through the tubing along the ceiling and edges of the brick room, connecting the plant beds to the fish tanks. When the plants take up the water, they absorb the nitrates they need to grow and the water filtered of these nutrients can be recycled back into the fish tanks.
“This way the fish are not swimming in their own feces,” said Funk. “We only have to add 10 percent of the water back every week that is lost to evaporation and transpiration.”
Funk explains how, despite offering a circular economy, the aquaponics farm still requires certain inputs and produces outputs. The LED lights that hang above the plants are the biggest input to the system as they are powered by electricity. However, The Plant is working on obtaining solar panels to power the lights with their pinkish, plant-friendly glow that come from a Chicago company called Happy Leaf.
The aquaponics operation was one of the first projects started at The Plant when it opened in 2011, and it is mainly used as a demonstration for education programming, according to Kassandra Hinrichsen, the education and outreach manager for Plant Chicago. While it’s not a perfect system, aquaponics farming uses about 90 percent less water than outdoor farming.
Hinrichsen said the goal is that people in the neighborhood, as well as visitors to The Plant, will learn how the system works and will be able to implement aquaponics as an urban gardening option in their communities. Household aquaponics systems are available commercially.
Photo at top: Plants thrive in the aquaponics system. (Credit: Colin Boyle)