Fish wastewater contains nutrients that can replace fertilizer.
Scientists and agriculturalists have used animal by-products such as bird and cow manure as fertilizer and energy sources for thousands of years.
The technology and the system by which we obtain the by-products has changed to become more cost effective.
"When fish eat, they retain about 40 percent of the nutrients in the food," said Jesse Chappell, associate professor in the Department of Fisheries and Allied Aquacultures.
The other 60 percent is excreted in the form of urine and feces.
In all systems, the water must be treated or the toxins produced by the urine and feces will kill the fish.
In most fisheries, the tanks the fish grow in have a biofiltration apparatus, an expensive and often complicated system that removes toxins from the water, Chappell said.
Chappell and his team of researchers, including horticulture professor Jeff Sibley, found a way to eliminate the biofilter.
Instead of treating the water, Chappell's system removes 1 to 5 percent of the water in the tank, depending on the biomass of the fish and replaces it with new water.
That small percentage of fish wastewater is then used as a fertilizer for some plants. Without a biofilter, bacteria can turn the waste into nitrate.
Nitrate doesn't bother the fish and plants love it, Chappell said.
The aim is two-fold: first, to grow healthy fish to market size and to use the wastewater those fish produce to fertilize plants.
Tilapia, a tropical fish, cannot grow in rural Alabama because they will die at some temperatures.
Using Chappell's system, Alabama fisheries can efficiently control the temperature of the water using aeration.
Chappell's aeration system only uses 3 percent horsepower to cool the temperature of 26,000 to 27,000 gallons of water.
"You couldn't tell the difference," Chappell said.
In a typical system, farmers fertilize plants at intervals that make sense to humans. However, in this new system, plants can be fertilized at intervals that make sense to them.
In one example, tomato plants were grown in a bed of calcite gravel.
The calcite is less dense than normal gravel, so the wastewater can be pumped through the system and sucked out.
In this way, the tomatoes can still receive food and nutrients, but their roots stay dry, Chappell said.
No independent places in Auburn are utilizing this revolutionary two-fold system currently, Chappell said.
But some catfish growers in West Alabama have begun to adopt the process.
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