Evolution of Aquaponics
by Scott Jones
Other than Mother Nature’s natural aquatic eco systems, aquaponics first appeared at least 1,500 years ago in China. One entrepreneur got tired of dragging feed out to the ducks, the finfish and the catfish. He stacked the ducks in cages above the finfish and moved the catfish downstream from the finfish. Now when he fed the ducks their droppings and uneaten food fell into the water with the finfish. The finfish ate and “processed it.” The wastes from the finfish flowed downstream and sank to the bottom, giving food to the catfish which are natural bottom feeders and scavengers. The processed feed and anything that the catfish missed was channeled out to the fields to feed the rice crop. He fed once and harvested four times. The only drawback was that it was outdoors, so it got cold. Everything froze up for 5 months of the year. The theory was good but the execution left a little to be desired.
Aquaponics is back in the news today, not because it’s the “newest rage,” but because it solves many of the vexing problems that strike traditional soil-based growers worldwide.
Water is a scarce commodity. Without clean drinking water humans don’t thrive. And yet, up to ¾ of our fresh water is used to water crops and then it rapidly drains away. Not only is the farmer’s hard-earned money draining away into the ground but, also, as the water drains away, it collects fertilizers and farm chemicals, leaching them into the ground water (our drinking water). The excess fertilizers and chemicals flow into our rivers and bays causing algae-blooms and killing the aquatic life. Roughly 10% of the chemicals that a soil farmer spreads on his fields are actually taken up by his plants, the rest goes on to wreak havoc on the natural life down-stream.
Modern aquaponics recycles water, reusing this valuable resource. The air is also recycled. The fish give off carbon dioxide (CO2) as they “breathe”. The plants take in the CO2, strip off the carbon (C) to build their leaves and release the remaining oxygen (O2) molecules. That oxygen-rich air is filtered and then blown into the water for the fish to recycle. In every aquaponic system wastes in one part of the system are utilized as a resource in another part.
The controlled environment (greenhouse) commercial aquaponic industry is in its infancy, both in the U.S. and around the world. Currently there are less than five large-scale (+1 acre) facilities around the world and only two in the U.S. While several smaller operations are scattered around the country, most are on the “family farm” scale, rarely exceeding ¼ acre.
All large-scale aquaponic operations are using either Nutrient Film Technique (NFT) or floating bed hydroponic systems combined with either rectangular or round fish culturing tanks. Most small-scale aquaponic operations are using the simpler Ebb & Flow hydroponic systems with small round fish culturing tanks.
Several species of fish have been cultivated successfully in aquaponic systems. Current technology limits the choices to fresh-water species, though recent research has shown promise on medium salt-water (brackish water) species such as Hybrid Striped Bass and shrimp. By far the largest share of the aquaponic fish market, in both pounds harvested and number of commercial operations, goes to Tilapia. Tilapia has several attractions for commercial operation: they have a short cycle from birth to harvest (6-9 months), tolerate drastic swings in water quality and are tolerant of low oxygen levels for extended times. Unfortunately, the farm-gate price, direct to wholesalers or haulers, is barely above the break-even costs. Tilapia is a great species with which to start a system, but a poor choice for the long-term operation of a viable commercial facility.
Nearly all plants can grow in an aquaponic system but only a few have been tested and proven to be economically viable. For the most efficient operation of a commercial aquaponic facility, a steady condition must exist between the pounds of fish (including the relation to fish feed) in the system and the poundage of plants in order to prevent toxicities and deficiencies of various elements from developing over time for both the fish and the plants.
Successful commercial aquaponic operations in the future will rely in part on three major modern technologies: co-generation of power and heat, tissue culture for plant propagation and advanced year-round breeding (most species of fish -other than Tilapia- are normally seasonal in their spawning). Controlled environment or greenhouse cultivation of high-value plants and fish requires a large amount of electricity available year-round without interruption for production lighting, ventilation and mechanization. Heat requirements can rise to as much as 40% of wintertime operating costs. Recent development of small, private, distributed grid electrical generators that sell excess electricity back to the main power grid, offer both constant and cheap electrical power that is readily available on-site.