Auburn University Associate Professor Jesse Chappell feeding fish that are part of an aquaponics project,
Multi-trophic aquaculture proves cost-effective
Friday, November 30, 2018, 02:50 (GMT + 9)
Auburn University’s Aquaponics Working Group has conducted research on multi-trophic aquaculture intended as a re-tasking process of production byproducts from catfish or tilapia to fertilize plants or to feed another aquatic species.
The team of scientists explains that fish waste naturally produces high concentrations of nitrogen that can be used to fertilize a variety of plants and feels confident that this approach helps to conserve nutrient resource inputs in feeding fish while still yielding maximum farming returns over a limited acreage.
“Fish are very efficient animals, but even they keep only about 25 percent of the feed they take in, turning it into fish biomass. It excretes the remainder of the nutrients in some form or another. That nutrient investment has value in whatever form we can capture. If we throw it away, we are literally throwing money away and then we have to pay an environmental price,” states Jesse Chappell, a member of the group and associate professor and Alabama Extension specialist in the College of Agriculture’s School of Fisheries, Aquaculture and Aquatic Sciences.
Auburn’s multi-trophic project actually began about 12 years ago with one greenhouse equipped with a fish production system and an adjacent greenhouse equipped for plant production but in the case of this new model, the greenhouses are de-coupled because plants can not be in the fish house, which leads to moist, creating an environment for increased disease pressure and incidence of plant losses.
Auburn University is researching and developing aquaponics, a process which takes nutrients from fish waste and uses it to grow vegetables. The College of Agriculture is partnering with Campus Dining to provide fresh food for Auburn students by using aquaponics.(Photo: Auburn University)
The new approach includes two production platforms that are hydraulically connected through the water system. The fish are fed, absorbing as much of the feed nutrients as possible and transforming the feed investment into fish biomass.
As a next step, the waste solids are processed within a part of the fish production system and warm water enriched with a good concentration of nitrates is brought over, which is what the plants need, which makes economic sense because so many cost points can be eliminated, since everything can be done on one tract of land to fully capture and re-task the investment made in nutrients, water and energy.
Auburn University Associate Professor Jesse Chappell is part of a multi-disciplinary research group at Auburn researching and developing aquaponics.(Photo: Auburn University)
“Using an Auburn-developed technology, we’d take the slaughter plant waste and turn it into fish meal, with no odor nor wastewater,” he said. “It’s a flash-drying technology that turns discarded processing waste into dry meal in about two minutes. We can sell or use that fish meal.”
The water recovery element will re-process the water from fish systems, taking the manure out of the water and digesting it to form methane or bio-gas to provide energy to help operate the machinery in the feed mill or processing plant.
Catfish are currently being produced in west Alabama for 85 to 92 cents per pound, and producers are selling them for 90 to 95 cents per pound.
Chappell states that a good pond manager with catfish or tilapia in Alabama might produce 10,000 pounds of fish per acre, but a very crude multi-trophic system routinely produces 350,000 to more than 1 million pounds of live fish per acre depending on the type system used.
Auburn’s aquaponics research has attracted more than USD 1 million thus far in competitive grants, according to School of Fisheries, Aquaculture and Aquatic Sciences professor Terry Hanson.
Source: Auburn University