Aquaponic Agriculture Holds Promise for Local Foods

Fish Waste Grows Veggies Without Soil

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D. Allen Pattillo is a specialist with the Iowa State University Fisheries Extension.

Posted: Wednesday, January 30, 2013 3:37 pm

AMES, Iowa -- An aquaponics experiment in Iowa is demonstrating that fresh greens and tasty fish can be produced almost anywhere in an economically and ecologically viable form of agriculture.

Aquaponics is a combination of aquaculture and hydroponics in which fish waste is used to organically create nutrient-rich water that allows plants to grow without soil.

Partly funded by the Leopold Center for Sustainable Agriculture in Ames, the experiment is being led by D. Allen Pattillo, a specialist with the Iowa State University Fisheries Extension. Pattillo is assisted by a number of ISU undergraduates.

The aquaponics system, located in a greenhouse on the ISU campus, was intentionally designed in a low-tech fashion.

“We kind of put a homemade system together with some 2-by-4s and extra tanks and things we had around,” he said. “So it took some ingenuity on our part to put this system together.” Pattillo said most existing aquaponics systems are “hobby-scale” operations. But, through his research, he hopes to help change that.

“My objective is to evaluate the sustainability of aquaponics, economically, ecologically and socially. A lot of people are really in to local foods, and they’re willing to pay more money for local fish. So, we like the idea that this can provide a local product to people, and fresh greens throughout the year. To reduce the carbon footprint, we want to grow species of fish that lower demand for energy resources and feed input.”

For these reasons, he chose Nile Tilapia, a mild breed of white fish that originated in Africa. Talapia live primarily on a plant-based diet, so they can thrive on soy proteins rather than more expensive feeds made of fishmeal.

Pattillo’s aquaponics system works like this: Fish are produced in 40-gallon tanks that each hold 33 fingerlings purchased from a hatchery in southern Iowa. They’re fed a commercial feed made of soy protein and a little fishmeal. Water is continuously circulated from the tanks into a system of mechanical and biological filters that capture excess feed and fish waste, which bacteria break down into nitrates that are consumed by the plants. The filtered water is then recirculated back to the fish tanks in a continuously flowing loop.

The fish are harvested after about four months, and the system is capable of growing a year-round supply of Buttercrunch bib lettuce inside the greenhouse. In warmer months, the research team also grows Italian large leaf basil, which can fetch as much as $25 a pound in local markets. Pattillo said his team chose lettuce and basil because they’re cheap and easy to grow, but the aquaponics system could theoretically grow a wide variety of fruits and vegetables.

“You can basically grow anything,” Pattillo said, although fruiting plants like tomatoes and cucumbers require more nutrients and have special lighting demands.

Pattillo said his research is testing three types of filtration media in an attempt to determine the most efficient and productive environment for the bacteria to do their work. The three media include rockwool, a lightweight material similar to insulation; pea gravel, which allows water to ebb and flow; and a floating raft system that allows roots to dangle directly into the tank of water.

A main focus of the study is to develop best practices for future large-scale commercial aquaponic systems. While Pattillo doesn’t see aquaponics as a potential replacement for existing commercial agriculture, he does believe the demand for fresh, local foods will make the technique a profitable alternative.

“Why I’m doing the research is so I can evaluate it economically and develop a plan, so I can tell people ‘if you grow this plant with this fish at this time of year, with this feed in this location, then you can make money.’ That’s really what my goal is,” Pattillo said.

“The price of vegetables goes up so much just because you have to take a tractor trailer and transport them from California or Florida and up to Iowa. People could sell a tomato for the same exact price here in Iowa, but make so much more money if they grew it locally. That’s a big deal for people to put more money in their pockets and create less emissions overall,” Pattillo said.

He said he gets questioned almost daily by people interested in the commercial application of aquaponics and he’s working with a national farm supply company to develop a “turn-key” commercial-scale system.

Iowa is also one of 21 states that participate in the MarketMaker program, which provides an online tool for local food providers to tap into regional markets, making it easier than ever to sell locally grown produce.

Aquaponic systems can also be implemented at institutions, Pattillo said. St. Gregory Retreat Center, an Iowa substance abuse rehabilitation facility, is working with partners to provide work and food to its clients.

“They have a small aquaponics operation on their site now," Pattillo said. "They’re using it to put food in their salad bar, but they’re also using it as a form of therapy for their patients. It’s been so successful that they are planning to expand the operation to a research and production center in Des Moines.” Pattillo said the center sells its produce to local restaurants, and the proceeds go toward scholarships to help the patients pay for their treatment.

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