TWO FARMS IN ONE: The aquaponic greenhouse at Cabbage Hill Farm in Mount Kisco, N.Y.
Image: John Matson / © Scientific American
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Confounded by the inexhaustible array of choices available when you stroll through a supermarket today? Well, here's another one to add to the list: How would you like your environmental degradation? By land or by sea? Whether it's pesticides and fertilizers leaching out of croplands or marine fish stocks vanishing by the boatful, every food purchase carries increasingly visible ecological costs.
Against this backdrop, a growing cadre of academics, farmers and aquaculturists is working to refine and popularize a technique that could slash those costs for both fish and vegetable products. The technique, dubbed "aquaponics," integrates fish farming and hydroponic agriculture in a sort of closed, symbiotic loop—the fish serve as fertilizer factories, the plants as water purifiers. The idea is to maximize food production while minimizing environmentally taxing inputs and potentially polluting outputs—a sustainable approach to growing healthy food.
At Cabbage Hill Farm in Mount Kisco, N.Y., a sizable aquaponic greenhouse offers an established proof of concept.
Slide Show: Take a Guided Tour of the Cabbage Hill Aquaponic System.
Six cylindrical tanks ranging in size from 1,000 to 3,200 gallons (3,785 to 12,100 liters) line the north side of the building, each home to hundreds of edible fish such as bass or tilapia. As the fish respire, their gills excrete ammonia into the water. Ammonia is a normal metabolic by-product but is toxic in sufficient concentrations, so it must be removed to keep fish healthy.
The key to aquaponics is that this waste is put to good use: In a churning bioreactor resembling a giant blue cauldron, ammonia-laden water drawn from the nearby tanks is processed by colonies of two helpful bacteria, Nitrosomonas and Nitrobacter. The former turns ammonia into nitrite, which the latter then converts to nitrate, a potent fertilizer. By using fish excretions to feed plants, "you don't have to buy all these fertilizers that are made from petroleum products and that take energy" to produce and transport, says agricultural scientist James Rakocy of the University of the Virgin Islands (UVI), a longtime proponent of aquaponics who has a demonstration facility at his institution. "Our fertilizer would be a waste product; instead we're using it to grow plants."
Growing food crops at Cabbage Hill takes place in long, shallow tubs on the south side of the greenhouse, which are filled with newly nutritious water from the bioreactor. On so-called rafts (repurposed polystyrene insulation panels) floating in the tubs, basil, bok choy and lettuce plants grow hydroponically—that is, without soil—their bare roots dangling through holes in the rafts to draw nutrients directly from the water below.
Stripped of its nitrate, the water is ready for return to the fish tanks, having essentially been filtered by the roots of fast-growing, edible, high-value plants.
Cabbage Hill's resident aquaponic guru, Kevin Ferry, views the process as an extension of natural nutrient cycles. "All we're doing is speeding up nature—the bioreactor is just composting," he says, comparing the churning aeration inside the cauldron with the turning of a compost pile.
As with any attempt to accelerate or enhance nature, aquaponics has costs and complications. During a tour of Cabbage Hill's facility, Ferry stops frequently to tinker with the systems—tossing handfuls of feed into a tilapia tank, adding lime to the bioreactor to bring up the water's pH (reduce its acidity), dipping his fingers into a bass tank and tasting the water to gauge its salt content (about eight parts per thousand, his taste buds register). "A place like this can't be left alone for very long," he acknowledges.
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14 Comments
Add CommentHow does the nutrient content of the vegetables compare to that of plants grown outdoors on organic soil? Toxicity of any kind?
Reply | Report Abuse | Link to thisUnfortunatly your right. For example, we have designed several electric cars that don't use gas at all and we like the hybrid more because that is less about our lives that we have to change. I learned all about the things people have discovered that would make our life so much easier on the enviroment. There are several reasons why we don't change, including: ignorance, convience, imediate cost, lack of intrest, and the simple fact that we are have a consumer market economy. None of those people care more about the enviroment then they do about making money, and those that do care usualy go out of buisness rather quickly because their prices are more expensive
Reply | Report Abuse | Link to thisBefore your write off this sort of project as "too expensive", consider that what you have seen here is merely 1 approach; there are more. I have been spending my "butter and egg money" for the same length of time as this farm, and I am just months away from a producing full scale closed loop system. I know what I have performs at a an equal or higher level of total efficiency, and is scaleable.
Reply | Report Abuse | Link to thisWhen one learns what this field of science can deliver, the whole concept of cost and payback is turned around. There will be many competing system approaches in the coming years, but all will be leveraging some aspect of this technology.
My approach was to marry the scientific understandings of biology and horticulture with the shared wisdom of 4th generation East Texas farmers; it's taken me a career of experiences to do this, and 7 years of working in the back yard to get to where we are now.
Bottom line folks, this stuff works, and you will be benefitting within a couple of years.
The costs and benefits of this new kind of system (although hardly new-- I was working for a aquaponics farm-- Bioshelter, in Sunderland, Mass-- 15 years ago) must be considered in relation to transportation costs and energy expenditures. According to the NYTimes, transportation fuels are not taxed by international agreement! That seriously skews the real costs of transportation-- basically subsidizing the costs of transporting foods across the world-- foods that are grown in wasteful conditions. If the playing field for energy consumption were leveled- perhaps the costs of aquaponically produced foods would appear much more reasonable.
Reply | Report Abuse | Link to thisI see great promise to this ecotechnology but it seems that community is a necessary requirement for these technologies to work. I mean dedicated people motivated by something more meaningful than Wall Street. Coincidentally, I visited the New Alchemy Institute (MA) in the 80�s where this veggies-fish and biological wastewater processes where at work just fine then. Why it didn�t take over the world since? I guess there is more profit in war.
Reply | Report Abuse | Link to thisThis system seems really efficient in breaking down and utilizing the nitrogen waste, but what about all the other macro and micro nutrients required by developing plants? Does this sort of system still need to import fertilizers to supplement these, or is it claiming the plants are sustained completely by the fish by product?
Reply | Report Abuse | Link to thisAnd this was funded by Mr. Carter's efforts during the end of the Carter Administration:
Reply | Report Abuse | Link to thisThe most interesting renewable thing in the area was south of that location -- Kaplan Slaughter. They had a perfect, except for size, operation where some 4000 vealers that were fed under a roofed area and their waste was washed into two, sequenced million gallon anaerobic fermentation tanks - financed with a million dollar grant obtained in the Carter renewables era. The neat part was a series of ponds to take care of the waste water overflow inter-fed by inverse gravity -- ending in a pond in which tilapia were raised -- as cat food -- and the bones returned to Kaplan's operation to be added to the feed. The biogas ran a power system that provided much of the electricity for the slaughter house. Just remnants of the operation remain -- too bad -- the size, it seemed to me -- was too small. But a feed lot -- without odors -- marvelous.
my pleasure
Reply | Report Abuse | Link to thismy pleasure
Reply | Report Abuse | Link to thisPut the tanks under the plants and set them in the desert in greenhouses. Use solar energy and wind energy to power the place, provide shade and use reverse osmosis and entropy recovery to keep water production higher than loss. Large enough tanks will stabilize the temperature. Pull nutrients from the salt water with algae. Work from the coasts inwards.
Reply | Report Abuse | Link to thisPut the tanks under the plants and set them in the desert in greenhouses. Use solar energy and wind energy to power the place, provide shade and use reverse osmosis and entropy recovery to keep water production higher than loss. Large enough tanks will stabilize the temperature. Pull nutrients from the salt water with algae. Work from the coasts inwards.
Reply | Report Abuse | Link to thisI would love to hear more about the system you have been "playing" for the last 7 years of your life! Anyway to learn more? Anemail address, a web site?
Reply | Report Abuse | Link to thisThanks
Roger Pilon, http://ponics.org
DIfferent strokes, different folks! Like cars, you can buy a Rolls Royce or a Smart Car. Some aquaponcis sytems are top of the line, computers, pumps, and so on.
Reply | Report Abuse | Link to thisOn the contary, some are very simple and low budget! Just type on Yahoo search: barrel ponics yahoo group. You will see! An aquaponic KISS system!
Roger Pilon
ponics.org
There is a consensus here, with mounting transport costs and a predicted human population explosion this proven technology needs to be rolled out now. We need elegant designs and cheap manufacture to produce village sized aquaponic units and set them up around the globe. A volunteer troubleshooter team needs to be able to travel globally quickly to rescue failing aquaponic farms, educate, upgrade and proselytize! aquaponics.me.uk
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