Auburn researchers: Fish wastewater an ideal way to grow plants

AUBURN – Teach a man to raise fish – and grow plants – and you’ll help feed his family and fellow citizens for a lifetime. That’s a new twist being applied to the age-old proverb at Auburn University, where researchers are combining fish farming and horticulture to help Alabama farmers find new income streams.

Jesse Chappell, associate professor in the Department of Fisheries and Allied Aquacultures and specialist with the Alabama Cooperative Extension System, is working with professor Jeff Sibley of the Department of Horticulture on the use of fish greenhouse wastewater to fertilize plants in an adjacent greenhouse.

“We want to provide an opportunity for farmers to have more on-farm income,” Chappell said. “We are seeking ways to produce plants more economically through new opportunities.”

The researchers, using an experimental setup with two greenhouses at the university’s E.W. Shell Fisheries Center just north of Auburn, are studying the nutrient amount and quality in fish wastewater that is piped from the fish greenhouse to the plant greenhouse. Chappell says fish retain 40 percent to 50 percent of nutrients but the rest are excreted, making the wastewater-production byproduct an excellent resource for plant nourishment. Many factors, though, affect the nutrients coming from the fish greenhouse. These variables include the number and kind of fish in a tank, the size of fish, the volume of the tank and the amount of water.

“We are quantifying the water and nutrient output in relation to stocking density and fish waste byproducts that can be used as biomass,” Chappell said. “This will help us determine baseline numbers so we can inform farmers of the right ratios regarding fish biomass and feed inputs applied as related to the amount and nutrient strength of wastewater.”

Horticulturist Sibley, who also serves Auburn as acting associate dean of the Graduate School, is growing several types of plants with the fish production water, such as herbs, bedding plants, ornamental shrubs, flowers and foliage, with the most potential residing in leatherleaf ferns, snapdragons and calla lilies. He is also studying edible plants, including tomatoes, sweet corn, peppers and strawberries. The study thus far indicates only one limitation in that fish water contains insufficient calcium, so it must be added when watering the plants.

The plants are harvested above ground, but the fish wastewater stays below ground at the root level. He says this setup is much cleaner than outside where birds, insects and rain can adversely affect plants.

“This project is very environmentally friendly as we use the unused fish production nutrients from aquaculture and reduce the amount of synthetic fertilizers used in horticulture crop production,” Sibley said.

The Auburn researchers are working with farmer Butch Wilson of Marion Junction, Ala., who is installing a full-scale operation that will have a 70-foot by 170-foot building with 10 intensive fish production systems. Wilson also will use fish wastewater to grow several plants including bamboo on outdoor plots that, in turn, will be used as fuel biomass to produce heat for the fish tanks.

Chappell says they also can produce methane from fish wastewater to heat, cool and power the building. This type of indoor fish production approach uses 40 percent to 50 percent less energy than traditional production systems in ponds to produce similar amounts of fish.

“There is much potential beyond normal farm setups as well,” Sibley added. “Empty warehouses and stores across the state could be converted into fish and plant production systems.”

The Auburn researchers, once they have collected and analyzed the data, will distribute the information to farmers through printed material and through educational aquaculture Web sites such as ALEARN ( The material will include nutrition details as well as how-to information so farmers can set up their own systems. They expect to begin making the information available by the end of 2009.

“We hope to develop a better profit margin potential for farmers willing to develop and manage this type production,” Chappell said. “These demonstrations and trials should help farmers and all the people of Alabama.”

(Written by Charles Martin.)

NOTE: High resolution photographs are available at Auburn University’s Newsmakers Web site (, which also contains a video news segment about the project.

Contact: Charles Martin, (334) 844-9999 (, or
Mike Clardy (334) 844-9999 (