If you’re a fan of homegrown arugula and mustard greens, you just may have the same taste as Tua, a 27-year-old Sumatran orangutan.

Tua lives at the Philadelphia Zoo, the first zoo in the country with its own on-site vertical garden used to grow leafy greens for its animals. And she loves the produce they’re feeding her.

The garden is located in a retrofitted shipping container in the Urban Green, the zoo’s open-air food marketplace. A mural, by Philly-based environmental artist and activist Eurhi Jones, transforms the front of the shipping container into a colorful collage of the animals who’ll chow down on the vegetation.

But the real beauty is inside, where stacked, tidy shelves hold rows of plants that are grown hydroponically, in nutrient-rich water instead of soil. LED lights, a substitute for sunlight, shine 18 hours a day. Farm operators use a mobile app to remotely control the container’s light, temperature, and humidity levels.

Kristen Lewis-Waldron, director of strategic initiatives at the zoo, said the vertical farm is far more sustainable than bringing in food from outside sources. It uses 70% to 90% less water than traditional farming, has no need for pesticides or herbicides, and cuts greenhouse gas emissions out of the equation, since no motor-powered transportation is necessary to get the food to the zoo.

“It really kind of creates this farm-to-table [model] — in this case, shipping container-to-exhibit,” she said of the project, which is in a pilot phase.

Lewis-Waldron is short on farming experience, but knows a thing or two about feeding animals. She landed her first role at the zoo 23 years ago as a nutrition intern. She went on to work for, and eventually lead, the zoo’s conservation department, before transitioning to her current position. Growing greens for the animals makes her feel like she’s come full circle, she said.

A peacock at the Philadelphia Zoo walks past the "Cropbox," a converted shipping container being used to grow plants being used to help feed the animals.
A peacock at the Philadelphia Zoo walks past the "Cropbox," a converted shipping container being used to grow plants being used to help feed the animals.

To launch the project, she enlisted the services of CropBox (which is also what the zoo calls the vertical farm), a North Carolina company that provides all the equipment customers need, including the shipping container, and helps set up the system.

Lewis-Waldron also consulted with industry experts, including those who operate their own vertical farms, to learn best practices and how troubleshoot technical challenges. All in all, the preparation process took about a year.

In its nine months of operation, the CropBox has fed 20 animal species with its microgreens. It produces 275 pounds of leafy greens a month, which is only 10 percent of the zoo’s monthly requirement. But that number, Lewis-Waldron said, will grow once the pilot year concludes and the project is expanded.

“You can take over a vacant warehouse or vacant building and convert it,” she said. “You could take six of these and make a dent in the requirements of our collection.”

The CropBox also benefits the zoo economically by replacing a collection of food it would otherwise purchase.

But perhaps most importantly, the greens grown in the vertical farm are rich in nutrients. The zoo takes animals’ diets very seriously, and even employs a full-time nutritionist. By feeding leafy greens to the animals, the zoo is keeping their health in shape.

Still, that doesn’t mean the greens are every species’ favorite snack. Just like humans, animals have unique palates. And the current variety growing in the CropBox — a stir-fry mix that includes arugula and mustard greens — isn’t always a crowd-pleaser.

“It’s got a little kick to it, a little bit of spice. Our emus were a little hesitant,” Lewis-Waldron said. “But our monkeys, langurs, apes, gorillas, orangutans, tortoises absolutely love it. So it’s interesting, and we’ll continue to test out different types of greens.”

This story has been adapted from a longer version that originally appeared in The Philadelphia Citizen.