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Aquaponica {{IPAc-en|ˈ|æ|k|w|ə|ˈ|p|ɒ|n|ɨ|k|s}} is een duurzaam systeem voor voedselproductie dat een combinatie maakt tussen traditionele aquacultuur (op laten groeien van zeewezens zoals slakken, vissen, krabben of garnalen in tanks) met hydroponica (het cultiveren van planten in water) in een symbiotische omgeving.

Een klein aquaponica systeem

Traditionele aquacultuur

In de traditionele gesloten aquacultuur worden vissen gekweekt in bakken. Hierdoor hopen afvalstoffen zich op in het water, wat voor toxiciteit voor de vissen zorgt. Het water dient normaal gesproken dan ook machinaal, biologisch of chemisch gereinigd / gefilterd en deels vervangen te worden.

Traditionele hydroponica

In de traditionele hydroponica worden planten direct gekweekt in water of word er water door bakken met kleikorrels, grint etc, gepompt. Om de planten hun voeding te geven dienen er constant voedingsstoffen voor de planten aan het systeem te worden toegevoegd.

Aquaponica

In de aquaponica word het afvalwater van de vissen omgezet door natuurlijke bacterien tot bruikbare stoffen voor de planten. De planten nemen deze stoffen op voor hun groei en zuiveren hierdoor het water waarna het weer teruggevoerd word naar de vissen. Door dit systeem verhelp je het probleem van de afvalstoffen in de aquacultuur en haal je de noodzaak van het toevoegen van voedingsstoffen in de hydrocultuur ook weg.

De term aquaponica is een samenstelling van de termen aquacultuur en hydroponica.

Aquaponica systemen verschillen in grootte van kleine binnen of buiten systemen tot grote commerciele systemen werkend op de zelfde technologie. De systemen bevatten meestal zoetwater, het is echter ook mogelijk om met zou water te werken. Met zoutwater dient er echter wel rekening mee gehouden te worden dat het aanbod in zoutminnende eetbare planten schaarser is dan bij zoetwater. De wetenschap achter aquaponica kan nog worden beschouwd als in de beginfase.

Function

Aquaponics consists of two main parts, with the aquaculture part for raising aquatic animals and the hydroponics part for growing plants. Aquatic effluents resulting from uneaten feed or raising animals like fish, accumulates in water due to the closed system recirculation of most aquaculture systems. The effluent-rich water becomes toxic to the aquatic animal in high concentrations but these effluents are nutrients essential for plant growth. Although consisting primarily of these two parts, aquaponics systems are usually grouped into several components or subsystems responsible for the effective removal of solid wastes, for adding bases to neutralize acids, or for maintaining water oxygenation. Typical components include:

• Rearing tank: the tanks for raising and feeding the fish;
• Solids removal: a unit for catching uneaten food and detached biofilms, and for settling out fine particulates;
• Biofilter: a place where the nitrification bacteria can grow and convert ammonia into nitrates, which are usable by the plants;
• Hydroponics subsystem: the portion of the system where plants are grown by absorbing excess nutrients from the water;
• Sump: the lowest point in the system where the water flows to and from which it is pumped back to the rearing tanks.

Depending on the sophistication and cost of the aquaponics system, the units for solids removal, biofiltration, and/or the hydroponics subsystem may be combined into one unit or subsystem, which prevents the water from flowing directly from the aquaculture part of the system to the hydroponics part.

Nitrification

Nitrification, the aerobic conversion of ammonia into nitrates, is one of the most important functions in an aquaponics system as it reduces the toxicity of the water for fish, and allows the resulting nitrate compounds to be removed by the plants for nourishment. Ammonia is steadily released into the water through the excreta and gills of fish as a product of their metabolism, but must be filtered out of the water since higher concentrations of ammonia (commonly between 0.5 and 1 ppm){{Citation needed|date=February 2011}} can kill fish. Although plants can absorb ammonia from the water to some degree, nitrates are assimilated more easily, thereby efficiently reducing the toxicity of the water for fish. Ammonia can be converted into other nitrogenous compounds through healthy populations of:

• Nitrosomonas: bacteria that convert ammonia into nitrites, and
• Nitrobacter: bacteria that convert nitrites into nitrates.

In an aquaponics system, the bacteria responsible for this process form a biofilm on all solid surfaces throughout the system that are in constant contact with the water. The submerged roots of the vegetables combined have a large surface area, so that many bacteria can accumulate there. Together with the saliency of ammonia and nitrites in the water, the surface area determines the speed with which nitrification takes place. Care for these bacterial colonies is important as to regulate the full assimilation of ammonia and nitrite. This is why most aquaponics systems include a biofiltering unit, which helps facilitate growth of these microorganisms. Typically, after a system has stabilized ammonia levels range from 0.25 to 2.0 ppm; nitrite levels range from 0.25 to 1 ppm, and nitrate levels range from 2 to 150 ppm.{{Citation needed|date=February 2011}} During system startup, spikes may occur in the levels of ammonia (up to 6.0 ppm) and nitrite (up to 15 ppm), with nitrate levels peaking later in the startup phase.{{Citation needed|date=February 2011}} Since the nitrification process acidifies the water, non-sodium bases such as potassium hydroxide or calcium hydroxide can be added for neutralizing the water's pH if insufficient quantities are naturally present in the water to provide a buffer against acidification. In addition, selected minerals or nutrients such as iron can be added in addition to the fish waste that serves as the main source of nutrients to plants.

A good way to deal with solids buildup in aquaponics is the use of worms, which liquefy the solid organic matter so that it can be utilized by the plants and/or animals.

Hydroponics subsystem

Plants are grown as in hydroponics systems, with their roots immersed in the nutrient-rich effluent water. This enables them to filter out the ammonia that is toxic to the aquatic animals, or its metabolites. After the water has passed through the hydroponic subsystem, it is cleaned and oxygenated, and can return to the aquaculture vessels. This cycle is continuous. Common aquaponic applications of hydroponic systems include:

• Deep-water raft aquaponics: styrofoam rafts floating in a relatively deep aquaculture basin in troughs.
• Recirculating aquaponics: solid media such as gravel or clay beads, held in a container that is flooded with water from the aquaculture. This type of aquaponics is also known as closed-loop aquaponics.
• Reciprocating aquaponics: solid media in a container that is alternately flooded and drained utilizing different types of siphon drains. This type of aquaponics is also known as flood-and-drain aquaponics or ebb-and-flow aquaponics.
• Other systems use towers that are trickle-fed from the top, nutrient film technique channels, horizontal PVC pipes with holes for the pots, plastic barrels cut in half with gravel or rafts in them. Each approach has its own benefits.

Most green leaf vegetables grow well in the hydroponic subsystem, although most profitable are varieties of chinese cabbage, lettuce, basil, roses, tomatoes, okra, cantaloupe and bell peppers. Other species of vegetables that grow well in an aquaponic system include beans, peas, kohlrabi, watercress, taro, radishes, strawberries, melons, onions, turnips, parsnips, sweet potato and herbs.{{Citation needed|date=February 2011}} Since plants at different growth stages require different amounts of minerals and nutrients, plant harvesting is staggered with seedings growing at the same time as mature plants. This ensures stable nutrient content in the water because of continuous symbiotic cleansing of toxins from the water.

Aquaculture subsystem

Freshwater fish are the most common aquatic animal raised using aquaponics, although freshwater crayfish and prawns may also be used. In practice, tilapia are the most popular fish for home and commercial projects that are intended to raise edible fish, although barramundi, Silver Perch, Eel-tailed catfish or tandanus catfish, Jade perch and Murray cod are also used. For temperate climates when there isn't ability or desire to maintain water temperature, bluegill and catfish are suitable fish species for home systems. Koi and goldfish may also be used, if the fish in the system need not be edible.

Normal operations

Aquaponic systems do not typically discharge or exchange water under normal operation, but instead recirculate and reuse water very effectively. The system relies on the relationship between the animals and the plants to maintain a stable aquatic environment that experience a minimum of fluctuation in ambient nutrient and oxygen levels. Water is only added to replace water loss from absorption and transpiration by plants, evaporation into the air from surface water, overflow from the system from rainfall, and removal of biomass such as settled solid wastes from the system. As a result, aquaponics uses approximately 2% of the water that a conventionally irrigated farm requires for the same vegetable production.{{Citation needed|date=February 2011}} This allows for aquaponic production of both crops and fish in areas where water or fertile land is scarce. Aquaponic systems can also be used to replicate controlled wetland conditions that are useful for water treatment by reclaiming potable water from typical household sewage.{{Citation needed|date=February 2011}} The nutrient-filled overflow water can be accumulated in catchment tanks, and reused to accelerate growth of crops planted in soil, or it may be pumped back into the aquaponic system to top up the water level..

The three main inputs to the system are water, feed given to the aquatic animals, and electricity to pump water between the aquaculture subsystem and the hydroponics subsystem. Spawn or fry may be added to replace grown fish that are taken out from the system to retain a stable system. In terms of outputs, an aquaponics system may continually yield plants such as vegetables grown in hydroponics, and edible aquatic species raised in an aquaculture.

History

Ancient

Aquaponics has ancient roots, although there is some debate on its first occurrence:

• Aztec cultivated agricultural islands known as chinampas and are considered by some as the first form of aquaponics for agricultural use where plants were raised on stationary (and sometime movable) islands in lake shallows and waste materials dredged from the Chinampa canals and surrounding cities are used to manually irrigate the plants.
• South China and Thailand who cultivated and farmed rice in paddy fields in combination with fish are cited as examples of early aquaponics. These polycultural farming systems existed in many Far Eastern countries and raised fish such as the oriental loach (泥鳅, ドジョウ), swamp eel (黄鳝, 田鰻), Common (鯉魚, コイ) and crucian carp (鯽魚) as well as pond snails (田螺) in the paddies.

Regions

North America

United States

While the development of aquaponics is often attributed to the various works of the New Alchemy Institute and the works of Dr. Mark McMurtry et al. at the North Carolina State University, many papers of initial development of aquaponics concepts pre-date both institutions by nearly a decade.

Tom and Paula Speraneo, owners of a small greenhouse operation near West Plains, Missouri, modified the North Carolina State method and raised tilapia in above-ground tanks inside a solar greenhouse. The effluent from the tanks was used to fertigate gravel-cultured vegetables in raised benches.

In addition, the Speraneos manipulated the watering cycle, and this methodology of the Speranos forms the basis for the style of "flood & drain" media grow bed aquaponics systems that have been widely adopted in Australia based on models promoted by Joel Malcolm and Murray Hullam, and are now gaining increasing popularity in the United States.

Inspired by the successes of the New Alchemy Institute and the North Carolina State University with aquaponics, other institutes followed suit. Besides the reciprocating aquaponics based on the techniques developed by Dr. Mark McMurtry et al. at the North Carolina State University, Dr. James Rakocy and his colleagues at the University of the Virgin Islands researched and developed the "Deep Water" or "Raft Culture" aquaponics The system combines tilapia with various vegetables.

In 1997 Rebecca L. Nelson and John S. Pade began publishing the Aquaponics Journal, a quarterly scientific journal that brings together research and various applications of aquaponics from around the globe.

Recent years have seen a shift towards community integration of aquaponics, such as the nonprofit foundation Growing Power that offers Milwaukee youth job opportunities and training while growing food for their community. The model has spawned several satellite projects in other cities, such as New Orleans where the Vietnamese fisherman community has suffered from the Horizon Disaster and in the South Bronx in New York City. In addition, aquaponic gardeners from all around the world have gathered in online community sites and forums to openly share their experiences and promote the development of this form of gardening.

Canada

The first aquaponics research in Canada was a small system added onto existing aquaculture research at a research station in Lethbridge.{{Citation needed|date=February 2011}} Canada saw a rise in aquaponics setups throughout the 90s, predominantly as commercial installations, that for example combine trout with floating lettuce production, or to water fruiting vegetable crops that warm up the water too much to be recirculated back into the fish ponds. Eels are also known to be raised.{{Citation needed|date=February 2011}} A set-up based on the deep water system developed at the University of Virgin Islands was built in a greenhouse at Brooks, Alberta where Dr. Nick Savidov and colleagues researched aquaponics from a background of plant science. The team made findings on rapid root growth in aquaponics systems, on closing the solid waste loop, and that because of certain advantages in the system over traditional aquaculture, the system can run well at a low pH level, which is favoured by plants but not fish. The Edmonton Aquaponics Society in Northern Alberta is adapting Dr. Savidov's commercially sized system to a smaller scale prototype that can be operated by families, small groups, or restaurants. They intend to further develop the closed solid waste loop.

South America

Barbados

Barbados is a densely populated island that deals with water scarcity. In 40 years' time, focus has shifted from domestic fruit and vegetable production on small farms to importing 80% of all fruits and vegetables for cost reasons. Aquaponics would make Barbados and other Caribbean islands less dependent on the world food market and reduce stress on the dwindling fish supplies. An inter-organizational project that started in late 2009 sets out to encourage and enable Barbadians to start aquaponics at home, with revenue generated by selling produce to tourists.

Asia

Bangladesh

Vegetable production part of the low-cost Backyard Aquaponics System developed at Bangladesh Agricultural University

Bangladesh is the world's most densely populated country. Most of its farmers use/misuse agrochemicals to enhance food production/storage life. However, the country is yet to establish a good monitoring system to ensure chemical-residue free safe food in the market, capable city dwellers are looking for a better way to grow their own safe foods for domestic consumption. To help support mainly this client group and people living in adverse climatic conditions such as salinity-prone southern part and flood-prone haor area in the eastern region, a low-cost model of backyard aqaponics system has been developed by Professor Dr. M.A. Salam at the Department of Aquaculture of Bangladesh Agricultural University, Mymensingh. The initial model has been developed in 2011, and demonstrated and reported to the press in January 2012. Further researches may be necessary to develop appropriate models for different situations among client groups.

Taiwan

Taiwan is a densely populated island that is faced with freshwater scarcity. Dispensation of water is government-controlled. The closed-loop system of aquaponics is used by agricultural farmers to save water by also rearing fish, while fish farmers grow plants that filter the water from the fish tanks. Taiwan Aquaponics Association is the not-for profit federation to promote Aquaponics at Taiwan. [27]

Japan

Japan is another highly densely populated country that has a long history of agricultural innovation and technological improvement. Aquaponics however, has only recently been introduced to this country, and there have been some projects to integrate aquaponics into communities in Tohoku, northern Japan, that suffered after the 2011 Tōhoku earthquake and tsunami. Japan Aquaponics, founded by Aragon St-Charles, is a leading social enterprise that is pioneering the use of aquaponics in this country.

Australia

Due to a ban on tilapia in all states except for Western Australia, native freshwater fish including Silver Perch, Jade Perch, Sleepy Cod, Murray Cod and Barramundi are popular in aquaponics and aquaculture systems, along with non-native Rainbow Trout, Brown Trout and Crayfish such as common Yabby and Redclaw.

Pros and cons

{{pro and con list|section|date=November 2010}} The unique advantages of aquaponic systems are:

• Conservation through constant water reuse and recycling.
• Organic fertilization of plants with natural fish emulsion.
• The elimination of solid waste disposal from intensive aquaculture.
• The reduction of needed cropland to produce crops.
• The overall reduction of the environmental footprint of crop production.
• Building small efficient commercial installations near markets reduces food miles.
• Reduction of pathogens that often plague aquaculture production systems.

Some conceivable disadvantages with aquaponics are:

• Initial expenses for housing, tank, plumbing, pumps, and grow beds.
• The infinite number of ways in which a system can be configured lends itself to equally varying results, conflicting research, and successes or failures.
• Some aquaponic installations rely heavily on man-made energy, technological solutions, and environmental control to achieve recirculation and water/ambient temperatures. However, if a system is designed with energy conservation in mind, using alternative energy and a reduced number of pumps by letting the water flow downwards as much as possible, it can be highly energy efficient.
• While careful design can minimize the risk, aquaponics systems can have multiple 'single points of failure' where problems such as an electrical failure or a pipe blockage can lead to a complete loss of fish stock.
• Like all aquaculture based systems, stock feed usually consists of fish meal derived from lower value species. Ongoing depletion of wild fish stocks makes this practice unsustainable. Organic fish feeds may prove to be a viable alternative that negates this concern. Other alternatives include growing duckweed with an aquaponics system that feeds the same fish grown on the system, excess worms grown from vermiculture composting, as well as growing black soldier fly larvae to feed to the fish using composting grub growers.

Gallery

• 
  The raft tank at the CDC South Aquaponics greenhouse in Brooks, Alberta

See also

• Aquaculture
• Horticulture
• Hydroponics
• Microponics
• Permaculture
• Symbiosis
• 養耕共生
• Acuaponia

External links

• Aquaponics Group on the University of Hawaii's AquacultureHub

Mediabestanden

Zie de categorie Aquaponics van Wikimedia Commons voor mediabestanden over dit onderwerp.