Students learn how ancient technique creates sustainable farming
Seventh graders in Deb Wimberly’s science class at Westwood Middle School in Manchester are learning first-hand about an ancient technique for sustainable farming that could revolutionize the food industry.
Known as “aquaponics,” the concept is believed to have begun in the time of the Aztecs. It consists of a symbiotic combination of aquaculture, or fish farming, with hydroponics, a way of growing plants in water instead of soil.
Waste generated by the fish, which are housed in a small aquarium, is pumped into a large, raised water tub, roughly the size of a pool table, framed in wood with a polyethylene liner.
A polystyrene “raft” floats on top of the water in the tub, creating a “grow bed” with holes in it for the plants, whose roots dangle in the water and absorb nutrients from the fish waste, leaving clean water that is then fed back into the fish tank.
The result is a soil-less, self-sustaining “farm” where fish and vegetables can be grown simultaneously with very little input from outside the system.
“I attended a once-a-week conference at the Tennessee STEM (science, technology, engineering and mathematics) Academy at Oak Ridge last year,” Wimberly said, “and they wanted us to put together an action plan for STEM education.
“Around the same time, I also went on a mission trip to the Dominican Republic, and that’s where I first saw an aquaponics system. The dirt is very hard down there.
“Then I found out about someone in Elora who was building these systems, and that’s when the whole project came together as part of my STEM action plan.”
Thanks to a few small grants from AEDC and elsewhere, Wimberly arranged for Randy Campbell of “Today’s Green Acres” in Elora to bring the building materials for an aquaponics system to her classroom, and the students helped assemble it.
“The system in Ms. Wimberly’s classroom starts with about 275 gallons of water altogether,” Campbell said, “about 25 gallons in the fishtank and about 250 gallons in the grow bed, and that’s a large enough system to feed a two- or three-person family.”
Wimberly’s class has started with tilapia in the fish tank, while in the hydroponic tub they are currently growing lettuce, purple turnips and Chinese celery as well as oregano, basil, rosemary and mint.
Together, she said, the two water-based sections will evolve into a self-contained ecosystem where bacteria break down the ammonia from fish waste into nitrites and nitrates, which are then absorbed by the plant roots as nutrients.
“Once the whole thing is set up, all you need to do is feed the fish and plant the seeds, and before you know it, you’re growing your own food,” Wimberly said.
Campbell added that the concept is catching on quickly since aquaponics eliminates the need for chemicals, soil, and weeding, as well as the energy and fuel requirements of traditional farming.
“With the proper FDA-approved, food-grade materials,” Campbell said, “the produce can also be fully certified as organic.
“This is the purest form of organic farming, really, because it can’t be ‘cheated,’ so to speak.
“Chemicals would kill the fish, so you know you’re getting clean, organic produce, and it uses 90 percent less energy since there’s no tractor, no diesel involved and no fertilizer added.
“The best part is that there’s no fuel used for transportation to get it to your home.
“Normally, food has to travel an average of 1,500 miles before it gets to your plate, and that takes at least 7-10 days, so you’ve already lost a lot of nutritional value by the time you get it.”
Campbell’s and other websites also claim that 95 percent less water is used, since the water circulates continually between the two tanks, with only occasional “topping off” due to evaporation.
Campbell also claims that it generates ten times more produce per square foot than in-soil farming.
“The older the system is, the more resistant it also becomes to environmental impurities,” he said, “because once the ecosystem is in place, it can absorb and break down various contaminants, as long as they’re not at extreme levels.”
While Wimberly’s fish tank is not the right type for breeding the fish, Campbell said larger systems can be assembled that allow for self-sustaining reproduction of the fish, too.
“The fish won’t reproduce in a clear tank because they feel too threatened,” Campbell said, “but on a larger scale, if you start with a non-transparent 150-gallon tank, you can put the breeders on one side and then grow the fish in the other side.”
For now, Wimberly’s class has stocked the fish tank with baby tilapia and will move the larger ones, as they grow, to a location that is yet to be determined.
“We’re eating the vegetables but I’m not sure how the students feel about eating the fish yet,” she said, “so we’ll cross that bridge when we get there.”
A wide variety of fish and prawns can be used in the fish tank, while almost any type of herb or vegetable can grow hyrodoponically in the grow bed.
“Everything except garlic, asparagus and potatoes can grow in it,” Campbell said, “because those are root plants that would stay under the water continuously.
“But we’ve grown the round carrots and we’ve even grown corn this way.
“The beauty is, you don’t have to have a green thumb and you don’t have to bend over and weed, so it’s one of the easiest ways to garden.
“And it’s scalable to any size, from an apartment, to a large green-house, to a giant commercial operation.”