About Food & Water Watch · 2017. 4. 5. · of aquaculture; recirculating aquaculture systems (RAS), coastal ponds and open-water net pens are a few major types. Open-water aquaculture

About Food & Water WatchFood & Water Watch is a nonprofit consumer organization that works to ensure clean water and safe food. We chal-lenge the corporate control and abuse of our food and water resources by empowering people to take action and by transforming the public consciousness about what we eat and drink. Food & Water Watch works with grassroots or-ganizations around the world to create an economically and environmentally viable future. Through research, public and policymaker education, media and lobbying, we advocate policies that guarantee safe, wholesome food produced in a humane and sustainable manner, and public, rather than private, control of water resources including oceans, rivers and groundwater.

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Copyright © September 2009 by Food & Water Watch. All rights reserved. This report can be viewed or downloaded at www.foodandwaterwatch.org.

About the Alliance for Sustainable AquacultureAlliance for Sustainable Aquaculture (ASA) is a collaborative group of researchers, business owners, non-profit organizations and interested members of the public working to further Recirculating Aquaculture Systems (RAS) in the United States through research, education, legislative work and advocacy. We believe that RAS, closed-looped and biosecure aquaculture operations, are the best option to meet our country’s need for a clean, green, sustainable, healthy seafood source to supplement our wild fisheries.

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On the Cover

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Images from left to rightMethane flame generated from waste captured by RAS.

Photo courtesy of Dr. Yonathan Zohar at UMBI Center Of Marine Biotechnology

Lettuce and other vegetables growing in RAS aquaponic tanks at UVI.Photo courtesy of Dr. James Rakocy at the University of the Virgin Islands in St. Croix.

Shrimp produced in a RAS facility at Blue Ridge Aquaculture.Photo courtesy of Mr. Martin Gardner from Blue Ridge Aquaculture in Martinsville, VA.

Nile tilapia, a species often produced in RAS.RAS tanks for raising tilapia.

Photo courtesy of Dr. Martin Schreibman at Brooklyn College, CUNY, Aquatic Research Environmental ssessment Center (AREAC)

This report is a joint project of the Alliance for Sustainable Aquaculture and Food & Water Watch.

Land-Based ReciRcuLating aquacuLtuRe systemsa more sustainable approach to aquaculture

Table of Contentsiv Executive Summary

1 Introduction

1 What Is RAS?

2 Types of RAS: Freshwater and Saltwater

3 Why RAS Can Be an Important Fish Production Method for the United States

4 RAS Factors

8 Research and Development

10 Future Improvements

12 Specific Commercial Case Studies

13 Conclusion

14 Endnotes

Executive SummaryThis report, Land-Based Recirculating Aquaculture Systems, provides an introduction to Recirculating Aquaculture Systems (RAS). RAS are closed-loop fish farming facilities that retain and treat water within the systems. This form of land-based aquaculture is quickly gaining popularity in the United States. Land-Based Recirculating Aquaculture Systems addresses why RAS could be an important method of producing more fish for the United States; highlights research, development and technical innovations in RAS; and discusses concerns and recommendations for the future of these systems. Land-Based Recirculating Aquaculture Systems also provides commercial case studies of existing successful RAS operations in the United States.

Consumer demand for cleaner, greener, safer seafood is on the rise. Many popular fish, like tuna, cod and certain snapper are depleted in the wild from many years of poor management, overfishing and other ecological problems like pollution and damage to key habitat areas. There is a need to supplement wild-caught fish to meet consumer demand for seafood. One method to produce more fish is known broadly as aquaculture — the rearing of aquatic animals in captivity. Aquaculture is also often called “fish farming,” as it can be likened to the farming of other food animals, like chickens, pigs and cattle. Aquaculture is increasing worldwide; between 2004 and 2006 the annual growth rate of this industry was 6.1 percent in volume and 11 percent in value.

Widespread open-water fish farming methods, such as coastal ponds and open-ocean aquaculture (OOA), can seri-ously damage marine ecosystems and are far from providing the safe and sustainable seafood many consumers want. In particular, OOA — the mass production of fish in huge floating net pens or cages in open ocean waters — raises concerns about consumer safety, pollution of the marine environment and conflicts with other ocean uses.

Fortunately, RAS can likely provide a cleaner, greener, safer alternative to open-water farms that does not compete with other ocean uses. These systems are usually land-based and reuse virtually all of the water initially put into the system. As a result, RAS can reduce the discharge of waste and the need for antibiotics or chemicals used to combat disease and fish and parasite escapes — all serious concerns raised with open-water aquaculture.

RAS provide a diversity of production options. Tilapia, catfish, black seabass, salmon, shrimp, clams and oysters are just a few examples of what can be raised in these systems. RAS can also be operated in tandem with aquaponics — the practice of growing plants using water rather than soil — to produce a variety of herbs, fruits and vegetables such as basil, okra, lettuce, tomatoes and melons. RAS range from small-scale urban aquaculture systems in individual homes to larger, commercial-scale farms that can produce fish and produce equaling millions of dollars in sales each year.

Currently, research and development is being conducted at academic, government and business facilities across the country to continuously improve the techniques and methods used in RAS. With innovations in waste management systems, fish feeds and energy usage, RAS has the potential to be a truly safe and sustainable aquaculture industry.

In recent years, the U.S. government has been shockingly insistent that development of open-water aquaculture, in particular ocean aquaculture, is the best way to have an increased seafood supply in the United States. Given the many ecological concerns associated with OOA, rather, the United States should be looking to explore more sus-tainable fish production, such as RAS. This report challenges natural resource managers and consumers to be more active in helping to promote a cleaner, greener, safer domestic seafood supply by learning more about RAS and re-questing grocery stores and restaurants carry RAS products rather than those from open-water aquaculture systems.

Alliance for Sustainable Aquaculture and Food & Water Watch

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What Is RAS?Recirculating aquaculture systems (RAS) are closed-loop facilities that retain and treat the water within the system. The water in RAS flows from a fish tank through a treatment process and is then returned to the tank, hence the term recirculating aquaculture systems.4 RAS can be designed to be very environmentally sustainable, using 90-99 percent less water than other aquaculture systems.5 RAS can reduce the discharge of waste, the need for antibiotics or chemicals used to combat disease, and fish and parasite escapes. RAS have been under development for the over 30 years, refining techniques and methods to increase production, profitability and environmental sustainability.6

Various methods can be used to clean the water from the fish tanks and make it reusable. Some RAS fish farms incorporate aquaponics — the practice of growing herbs and vegetables in water — into their system. Plants need 13 elements to grow; the wastewater from the fish tanks naturally provides 10 of these elements.7 The plants thrive in the nutrient-rich system water, and they actu-ally help to purify it for reuse — the plants absorb the nutrients and the “cleaned” water can go back to the fish tanks!

Consumer demand for cleaner, greener, safer seafood is on the rise. Popular species of wild fish are depleted,1 leaving many people looking to aquaculture to help meet

the demand for seafood. Aquaculture production — the rearing of aquatic plants and animals in captivity — is increasing worldwide; between 2004 and 2006 the annual growth rate was 6.1 percent in volume and 11 percent in value.2 There are many forms of aquaculture; recirculating aquaculture systems (RAS), coastal ponds and open-water net pens are a few major types. Open-water aquaculture systems are, as they sound, open to air and water, and can therefore have a risk of air- or water-borne contaminants.3 RAS are closed, controlled, bio-secure systems that retain and treat water within the system, reducing the risk of contamination from air- and water-borne contaminants.

Introduction


Land-Based Recirculating Aquaculture: A More Sustainable Approach to Aquaculture

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Types of RAS: Freshwater and SaltwaterRecirculating aquaculture systems can be divided into two main categories: freshwater and saltwater opera-tions. Each of these can be paired with specific technolo-gies designed to maximize efficiency within the system, minimize effluent discharge and occasionally to work in a symbiotic relationship with other technologies, re-viewed in brief below.

Freshwater RASFreshwater RAS can include the production of such fish as tilapia, catfish, eel or striped bass, among oth-ers. One innovative method explored in conjunction with freshwater RAS is aquaponics, as described above. Aquaponics works by allowing for the growth of plants, fish and nitrifying bacteria simultaneously — each of which feed off of the waste of the others to create a sys-tem that requires very little maintenance, aside from pH monitoring, to ensure optimal growth.8 A major concern of most aquaculture systems is the buildup of ammonia (NH3) and its derivatives from fish waste, which can be fatal to fish even at very small concentrations — as little as .08 mg/L. Aquaponic systems work by introducing nitrifying bacteria, which feed on the ammonia in fish waste to convert it into nitrate, which is non-toxic to the fish and beneficial for the plants.9 Another innovation in freshwater RAS involves the use of microalgae to reduce

the prevalence of carbon dioxide within these systems and provide a food source to developing fish.

Saltwater RASSaltwater RAS can take several forms as well, and are sometimes referred to as marine RAS. One type of sys-tem that has been researched extensively in recent years is the high-rate algal pond, or HRAP. HRAPs make use of macroalgae — seaweed — in order to reduce the amount of waste in RAS. In fully recirculating systems, nitrate and phosphate levels accumulate at a rate that is proportional to fish density; thus, the larger the produc-tion scale, the more effluents will appear in the system and need treatment in order to ensure the continued growth of the fish.10 Macroalgae can accomplish this be-cause they absorb the nutrients that are in fish waste for their own growth, the same way that aquaponics produce plant growth from these nutrients. The difference in ma-rine RAS is that the seaweed is generally not intended for consumption, and the seaweed will thrive in high-salin-ity environments, whereas land-based plants would not. Macroalgae HRAPs have been found to be even more productive in the removal of wastes than the microalgae that are used in freshwater systems, so this is considered a very viable route for marine RAS.11 One factor that is holding back more extensive use of the HRAP system is that seasonality can affect the productivity of micro- and

An example of a small-scale RAS.Photo by Eileen Flynn


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macroalgae alike — with higher productivity rates in the warmer, brighter summer months.

Why RAS Could Be an Important Fish Production Method for the United States

How RAS FunctionA key feature of RAS is that it re-uses water; the water is recirculated continuously throughout the system. All of the tanks and various components in RAS are connected by pipes. Water flows from the fish tank to the mechani-cal filter where solid waste is removed. The water then flows into a biological filter that converts ammonia to nitrate. Some RAS incorporate plant tanks as a biologi-cal filter – plants absorb nutrients, thus “cleaning” the water. Other systems use special tanks that are designed to promote good bacteria growth – the bacteria act as a filter. After being “treated” in the mechanical and biofiltration components, the water flows back to the fish tank.

BiosecurityRAS fish farms are often fully closed and entirely con-trolled, making them mostly biosecure — diseases and parasites cannot often get in. Biosecurity means RAS can frequently operate without any chemicals, drugs or antibiotics, making a more natural product for consum-ers. Water supply is a regular route of pathogen entry, so RAS water is often first disinfected or the water is obtained from a source that does not contain fish or in-vertebrates that could be pathogen carriers (rain, spring or well water are common sources).12 Biosecurity in RAS requires that the systems be designed for easy clean-ing, completely and frequently, to reduce pathogens.13 Being self-contained and cleaner also means RAS can be located near markets or within land-locked communi-ties that will use the fish, rather than by natural water sources like oceans or rivers — RAS does not need to be located on water to supply the system or for drainage. Locating RAS by the markets or communities they serve means they can have a smaller carbon footprint due to reduced shipping distance and provide a fresher product to the consumer.

Water Reuse RAS are completely contained systems that reuse most of the water from the fish holding tanks. Wastes are removed; water is treated and then recycled back to the tanks. Ideally, RAS only replace very small percentages of the total water volume, due to some loss during waste removal and/or evaporation (less than 1 percent daily water exchange).14 This low replacement volume is espe-cially important in saltwater systems since salt water can be more expensive and more difficult to make or obtain than fresh water.

Space and Production EfficiencyRAS production levels are often higher than those in oth-er forms of aquaculture. RAS control the environmental conditions in which products are raised, thus allowing for optimal year-round growth.16 Some RAS can produce market-sized fish in just nine months, compared to the 15 to 18 months it often takes for the fish raised in other

Open-Water AquacultureOpen-water aquaculture, (when in the ocean, also known as offshore aquaculture, ocean fish farming, open-ocean aquaculture and other, similar terms), is the mass production of fish in coastal ponds, or large floating pens or cages in ocean waters. Just one farm is a large-scale operation.

While open-water fish farming is a fairly common practice worldwide (we don’t do it large-scale in U.S. waters currently) it can pose real threats to human health and the environment:

• Fragile habitat can be permanently damaged from clearing out space to site the farm or from anchors to hold down cages.

• Fish in cages can spread diseases to wild fish, or escape and intermix with wild fish, interfering with or even overtaking natural populations.

• Open-water fish farms allow free flow of water between the fish enclosures and the ocean. Concentrated amounts of fish food, wastes, diseases and any chemicals or antibiotics that may be used in farms can flow straight into open waters, polluting habitat and wildlife and impeding recreational water uses like swimming and diving.

• Chemicals used in production may remain in the fish and be transferred to people who consume them later.

Because there are so many potential problems with open-water farms, the United States should explore other options, like RAS.


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systems to grow to market size.17 It takes 197.6 acres of open ponds to produce the same amount of shrimp that a RAS farm can raise on just 6.1 acres.18 Tilapia, cobia, black sea bass, branzini, salmon, trout and shrimp are among the many seafood products being raised in RAS. Aquaponic RAS produce a large array of herbs, vegeta-bles, fruits, flowering plants and seaweeds as well.

RAS Factors

Water Quality and Waste ManagementThe critical water quality parameters in RAS are dis-solved oxygen, temperature, pH, alkalinity, suspended solids, ammonia, nitrite and carbon dioxide (CO2).19 These parameters are interrelated in a complex series of physical, biological and chemical reactions.20 Monitoring and making adjustments in the system to keep the levels of these parameters within acceptable ranges is very important to maintain the viability of the total system. The components that address these parameters can vary from system to system.

Dissolved OxygenOxygen that is dissolved in the water is called dissolved oxygen or DO. Fish take in DO from the water through

their gills. The amount of DO that a fish needs to stay alive and grow depends on the species and size of fish, as well as the effects of the other water quality param-eters.21 A fish with a higher metabolic rate will consume DO at a higher rate. 22 Oxygen is also critical to the meta-bolic processes of the bacteria living in the system that break down ammonia and solid waste.23

Low levels of DO in the system can reduce productivity of the fish and bacteria, ultimately resulting in mortali-ties. DO levels are monitored as water is leaving the fish tank or the biological filter (where a large amount of bacteria lives) to accurately access the level of DO that is available to fish and bacteria respectively.24

DO can be maintained in RAS through aeration, either with atmospheric oxygen (air) or pure oxygen. Standard sources of air in aquaculture are blowers, air pumps or compressors. The primary differences between these options are the water and DO pressure requirements and volume discharged.25 Airstones, pieces of limewood or porous rock, are often used to release the air into the water.26 Pure oxygen sources are used when diffusing atmospheric oxygen (air) into the system cannot keep up with the consumption of DO by the fish and bacte-ria. Three sources of pure oxygen often used for RAS are high-pressure oxygen gas, liquid oxygen and on-site

Oxygen dissolving into a RAS.Photo by Eileen Flynn


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generators.27 U-tube aerators, packed columns, low head oxygenators and down-flow bubble contactors are component options for diffusing pure oxygen into the system water. These components are all designed to use a counter-flow of water and oxygen to enhance the gas-liquid interface forcing more oxygen to dissolve into the water.28 In general, warm-water fish grow best when DO concentrations are above 5 mg/L.29

TemperatureFish are cold-blooded; the temperature of the water in which they live controls their body temperature. Water temperature directly affects the physiological processes of fish such as respiration rate, efficiency of feeding and assimilation, growth, behavior and reproduction.30 Fish are often grouped into three categories based on pre-ferred temperature ranges: cold-water species below 60 degrees Fahrenheit, cool-water species between 60 F to 68 F and warm-water species above 68 F.31 To ensure maximum growth and minimize stress, temperatures need to be maintained in the species’ optimal range. Indoor RAS allows the farm to have greater control over the temperature of the ambient air that can impact the water temperature. Heaters and chillers can be added to RAS to maintain temperature, though this is not ideal in terms of energy efficiency.

At Skidaway Institute of Oceanography, Dr. Richard Lee, an emeritus professor of oceanography, uses geothermal chilling and solar heating to regulate the temperature of his RAS. The geothermal chilling is conducted through a closed-loop pipe running down into the groundwa-ter and back up to the surface (no water is exchanged between the facility and the groundwater). The ground-water is approximately 64.5 F and the contact of the cool water on the outside of the pipe transfers the heat so that the tank can maintain its temperature between approxi-mately 79 F and 82.5 F during a Georgia summer.32 The solar heating is conducted by running pipes carrying system water through sheets of black plastic that trans-fer the heat they absorb from the sun to the water in the pipes. Using this method the RAS system had tempera-tures between approximately 70 F and 77 F in the winter when air temperature was not above 60 F in the same time period.33

pH and AlkalinityMonitoring of the pH level is among the most im-portant tasks in RAS. The pH is directly affected by

concentrations of ammonia from fish wastes. When fish waste is produced, most of it eventually breaks down into nitrate, and nitrate accumulation tends to produce a drop in pH and alkalinity, which can be harmful to fish if it is not monitored properly.34

The scale of pH ranges from 0 to 14, with lower numbers demonstrating increased acidity and higher numbers showing greater basicity. Seven is considered the equi-librium point of freshwater, where it is neither acidic nor basic. In freshwater RAS, pH is generally maintained around 6 to 7.5. In aquaponic systems, pH may be main-tained at a slightly lower level (around 5.5 to 6.5), where the slightly higher acidity level helps plants to obtain nu-trients. Some studies have been done in aquaponics sys-tems to reconcile the lower optimal pH of plants with the higher optimal pH of fish, and it has been found that a pH as high as 7 can be maintained without reducing the productivity of plants.35 Marine RAS needs to maintain a slightly higher pH, as the average pH of ocean saltwa-ter is around 8, which makes it somewhat basic. People who work with recirculating systems need to monitor pH carefully in order to keep levels within an accept-able range for health and growth of the fish. Some of the aforementioned technologies, such as high rate algal ponds, can act as a counterbalance to the accumulation

pH testers.Photo by Eileen Flynn


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of certain chemicals within an RAS and can help to bal-ance pH levels naturally.

Alkalinity is a measure of the pH-buffering capacity of water.36 The principle ions that contribute to alka-linity are carbonate (CO3

-) and bicarbonate (HCO3-).

Supplements may be added to water to adjust the alka-linity. Alkalinity of fresh water ranges from less than 5mg/L to more than 500mg/L and salt water is about 120mg/L CaCO3.

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Waste Removal: Ammonia, Nitrite, Nitrate, Solid and Suspended Waste (Without Aquaponics)One major benefit of RAS over other forms of aquacul-ture is the ability to capture, treat and/or utilize waste from the system. In general, solid wastes, including feces and uneaten feed, are filtered and removed from the system. Once removed, these solids can be treated or utilized in a secondary function (converted to energy, fertilizer and possibly even feed). Systems that do not effectively and quickly remove fish fecal matter, uneaten food and other solids from the water will never produce fish economically.38

Nitrogen is required in small amounts by fish for good health and growth. Nitrogen that is not utilized by fish becomes nitrogenous waste in the system and needs to be removed. There are several sources of nitrogenous waste including: feces, urine, excretions from gill dif-fusion, uneaten food and dead and dying fish.39 The decomposition of these nitrogenous compounds is par-ticularly important because of the toxicity of ammonia, nitrite and to some extent nitrate to fish.40 Ammonia exists in two forms: non-ionized NH3 and ionized NH4

+. Non-ionized ammonia is the most toxic form, due to its ability to move across cell membranes.41 An increase in pH, temperature or salinity increases the propor-tion of the non-ionized form of ammonia.42 Nitrite is the intermediate product in the process of nitrification of ammonia to nitrate and is toxic because it affects the blood’s ability to carry oxygen.43 In RAS, effluent water is passed through a biofilter containing bacteria that converts ammonia to nitrite and finally to nitrate.44 This conversion from ammonia and nitrite to nitrate is called nitrification; the bacteria in this process require ample amounts of oxygen.45 Plants in an aquaponic system will act as the biofilter converting ammonia and nitrates. In RAS facilities without plants in the system (aquaponics), the biofiltration component consists of media with living beneficial bacteria that converts harmful ammonia and nitrite to nitrate. Algae and bacteria floating in the water column can also convert ammonia to nitrate.46 Nitrate is the end product of nitrification and is the least toxic; it can be removed from the system by daily water changes or denitrification.47 Denitrification is the process of converting nitrate to nitrogen gas; the bacteria in this process do not require oxygen.48

Treatment processes for recycling water at the USDA ARS National Cold Water Marine Aquaculture Center, Franklin, ME.

Photo courtesy of Dr. Steve Summerfelt of the Freshwater Institute, Shepherdstown, WV.


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Carbon dioxideDissolved carbon dioxide is another product that can accumulate in high-density RAS. Large-scale RAS systems must supplement their tanks with pure oxygen for a greater quantity of fish to be bred, but this results in insufficient natural removal of the carbon dioxide (CO2) that is then produced.49 (In lower-density systems, oxygenation is generally unnecessary, as sufficient water exchange and aeration occurs to naturally balance levels of both oxygen and CO2.)

Excessive levels of CO2 can result in changes in pH towards acidification, which can be detrimental to fish if the pH level drops too low. Various technologies have been tested to reduce the amount of carbon dioxide in the water of these high-density systems. One method of addressing excessive carbon dioxide is the use of chemi-cals, which can balance pH levels and thereby eliminate the CO2 in RAS.50 Sodium hydroxide and sodium bicar-bonate are two chemicals commonly used in aquaculture for this purpose. Both function by increasing alkalinity in the water, resulting in a series of chemical reactions

which break down carbon dioxide and reformulate it into lesser molecules.

Another process for carbon dioxide elimination is called aeration stripping, a process in which water is forced through a series of cascading “stripping columns” that expose the water to air and result in the release of dis-solved CO2 into the atmosphere. Experiments have been done to determine the optimal ratio of air to water as it cascades through the stripping columns, and for now, experiments suggest that higher ratios of air to water — implying a slower filtration process — improve the efficiency of carbon dioxide stripping from a recirculat-ing system.51

Similar to aeration stripping, a third type of carbon dioxide removal is performed by vacuum degassing, a process that vents excessive gasses through a vacuum or pump system. The process of carbon dioxide elimination is similar to the manner in which it is eliminated in the aeration stripping process.52

Basil grown in a RAS aquaponics tank at UVI.Photo by Eileen Flynn


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The overall waste-capture efficiency of a full RAS facility can be 100 percent.53

Researchers and industry experts are developing a vari-ety of resourceful ways to deal with the waste produced by RAS fish farms, such as creating fertilizer for crops and plants. Some RAS farms turn the waste into pellets to create a feed ingredient for other fish or shrimp. Still other RAS turn the waste into methane gas, which can be used to help power generators. 54

Research and DevelopmentCurrently, research and development is being conducted at academic, government and business facilities across the country to continuously improve the techniques and methods used in RAS to offer consumers cleaner, green-er and safer products.

Urban Aquaculture as a Community-Based Option Dr. Martin Schreibman, founder and director of the Aquatic Research and Environmental Assessment Center at the City University of New York’s Brooklyn College,

is conducting research on RAS he calls “urban aquacul-ture.” Dr. Schreibman is working with RAS of various sizes that can be run virtually anywhere, in warehouses, on brownfield sites or right in your own home, utilizing the hydroponic component of aquaponics to clean the water. One aspect of his research involves “aeropon-ics,” in which plants are suspended above the tanks and sprayed with system water every 10 to 15 minutes instead of being submerged in the water.55 This process reduces the horizontal space needed to run the system when compared to other aquaponic systems. “Urban aquaculture” can be located in or near populated areas, so it can provide positive socio-economic benefits — like jobs — as well as fresh, safe seafood and produce to local markets.56

Larger-Scale Aquaponics Dr. James Rakocy, director of the University of the Virgin Islands Agricultural Experimental Station, con-ducts RAS aquaponic research in a large-scale system with plants growing on floating rafts. Foam rafts float on the surface of large water-filled hydroponic tanks. Plants develop and expand atop the rafts, basked in sunlight, while roots get maximum exposure to water by growing

This is an urban aquaculture/aquaponics system (it grows both fish and plants) in a small setting — in fact it is in a part of a classroom at Brooklyn College!Photo courtesy of Dr. Martin Schreibman at Brooklyn College, CUNY, Aquatic Research Environmental Assessment Center (AREAC)


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beneath. Raft tanks have no size limitations. A disad-vantage of raft culture — exposing the roots to zooplank-ton and snails that may grow in the tanks — is addressed through the addition of ornamental fish (tetras) and red ear sunfish to consume these pests.57 Additional research has been done refining waste management components and water quality needs for optimal plant and fish growth. Dr. Rakocy’s research shows the tech-nology UVI uses can be applied for an individual family subsistence or commercial scale, while conserving water and recycling nutrients. Researchers at the UVI facility grow tilapia and continue to experiment with basil, okra, lettuce, watermelon, mint, chives, tomatoes, cantaloupe, cucumber, flowers, squash, bok choy, collard greens and sorrel (a locally grown plant used in a popular drink) and other crops. The UVI commercial-scale aquaponic sys-tem can annually produce up to 35,570 pounds of tilapia and vegetables on 1/8 an acre of land.58

Various Species Grown in RASThe list of aquatic species being researched and grown in RAS is constantly broadening to include: oysters, blue crabs, sea bream, branzini, cobia, red drum, black seabass, bivalves, soft corals, horseshoe crabs, assorted flatfish, lobster, nautilus, tilapia, rainbow trout, striped bass, salmon and assorted shrimp.

The list of plants that are grown in conjunction with these aquatic species is also growing rapidly, including: algae, seaweeds, basil, okra, lettuce, watermelon, mint, chives, tomatoes, cantaloupe, cucumber, flowers, squash, bok choy, collard greens, sorrel, arugula, peas and vari-ous pharmaceutical plants

Fish Feed Existing RAS farms and researchers are working to feed their fish a more environmentally sustainable diet while remaining nutritionally appropriate. One of the biggest and most crucial hurdles faced by aquaculture has been to decrease the amount of wild fish used as an ingredient in fish feed. Traditionally, large amounts of wild fish are used to produce the pellet feed for farmed fish. Taking prey fish from the oceans to feed farmed fish can deplete ocean food chains and disrupt ecological balance. Work is being done at various RAS farms to improve feed, including reducing the amount of fish needed to be put into feed; finding alternative feed ingredients (includ-ing worms and algae);59 and even using waste to create a healthy feed source.

Dr Richard Lee at Skidaway Institute of Oceanography has found a unique solution to raising carnivorous fish without taking wild fish. At the Skidaway RAS facility Dr. Lee grows black seabass to a market size of two pounds in one year by feeding them whole tank-raised tilapia. The feed conversion rate is five pounds of tilapia to one pound of black seabass. The seabass grow twice as fast when they are fed tilapia, when compared to being fed the traditional fishmeal pellet. Feeding a tank-raised freshwater fish to a saltwater RAS raised fish also reduc-es the chance of pathogen introduction.

A majority of commercial feeds use soybean as a com-mon protein replacement for fishmeal and fish oil. There are some concerns with using soybean, a terrestrial protein, in fish feed. In 2009, 91 percent of soybeans grown in the United States were genetically modified.60 Another concern is that soybeans are high in estrogen and do not occur naturally in the aquatic environment.61 In addition, soy protein is quite expensive. Many re-searchers are looking to replace soybeans in feed with other proteins that occur naturally in the aquatic en-vironment, like algae, that could increase the financial sustainability of RAS.

Fish feed pellets.Photo by Eileen Flynn


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Future Improvements RAS is not yet perfect, but the benefits of a controlled, closed system with waste management should not be overlooked. Additional research is being done to devel-op new techniques and methods to continually improve RAS.

Chemical UsageWater supply is a common means of pathogen entry. Water for RAS is often disinfected, or obtained from a source that does not contain fish or invertebrates that could be pathogen carriers (rain, spring or well water are common sources).62 Biosecurity in RAS requires that the systems be designed to be cleaned easily, completely and frequently to reduce pathogens.63

When diseases do appear, a veterinarian and diagnos-tic laboratory should be involved in determining the specific disease and treatment, using chemicals that are approved for use in food fish production.64 Many RAS can operate without any chemicals, drugs or antibiotics, making a more natural product for consumers.65

Energy UsageRAS facilities require varying amounts of energy to run the machinery that moves the water through the system and treatment processes. Some producers using aqua-ponics and facilities raising shrimp may be able to use fewer pieces of machinery to run the systems therefore having reduced energy demands. Research is being done by Dr. Timothy Pfeiffer at the U.S. Department of Agriculture’s Agricultural Research Service to de-termine the specific energy requirements for different aspects of the treatment processes and how to get the most efficient water treatment with the least amount of energy.66 Dr. Yonathan Zohar, Director at University of Maryland Biotechnology Institute’s Center of Marine Biotechnology (COMB), is using waste captured from RAS to produce energy in the form of methane that can be fed straight into a generator.67 Dr. Zohar and researchers at COMB are also working to convert algae biomass, produced in RAS, into bio-fuel.

Both freshwater and marine RAS have been the sub-ject of experiments to enhance energy efficiency. Implementing solar heating for the maintenance of proper temperature within the fish basin has been found to reduce conventional energy requirements by 66 per-cent to 87 percent, depending on the regional climate

where the RAS are located.68 Wind energy has also been tested as a means to power reverse-osmosis membrane filtration, which separates purified water from a concen-trated “brine” of fish effluent, with some success.69 Many of these technologies have been proven viable at a small-scale, and implementation on large-scale (high-density) RAS are ongoing.

Feed EfficiencyIn the production of farm-raised fish, the feed plays a large role in determining sustainability and quality of farmed fish. Farmed fish are often fed wild forage fish, such as anchovies, sardines and herring, after being processed into fishmeal or oil. These prey fish are a crucial part of the marine ecosystem, serving as food for marine mammals, birds and large predatory fish. Since



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taking these fish from the oceans can disrupt food chains and ecosystem balance, feed conversion rate is always a concern with farm-raised fish. The ideal feed conver-sion is one pound or less of wild fish to raise one pound of farmed fish. Although existing feed sources do not always have completely efficient 1:1 conversion rates, RAS farms and scientists are conducting research and developing techniques that can improve feed quality and reduce the need for wild fish. Examples of innovations in RAS feed efficiency include finding alternative feed ingredients, such as worms and algae, improving feed quality by using algae to increase protein content and raising prey fish in RAS, instead of harvesting wild for-age fish, to feed larger predatory fish.70

“Organic”?Organic foods are produced under conditions in which all inputs are controlled. RAS is the only method of raising fish that can completely control the production environment. Being a closed-loop system, RAS can better ensure fish and plants are not being exposed to synthetic fertilizers or pesticides, growth hormones, sewage sludge, antibiotics or any other artificial feed or

treatments. Other forms of aquaculture that allow water to flow freely in and out of the holding ponds or cages can not control what chemicals and pollutants are being carried with the water. Some RAS/aquaponic facilities have been certified organic for the plants produced.

Not a Natural Environment, but Still a Healthy One To achieve economic viability, RAS farms run their sys-tems with a higher density of fish per tank than would be found in the wild. Density depends primarily on water quality, fish species and size.71 Overcrowding of younger fish is avoided to allow them optimal room to grow dur-ing their rapid growth stage.72 As fish grow they may be moved to reduce densities to maintain good water quality and to optimize fish health and growth until they reach market size. RAS fish farmers avoid keeping fish at densities that can be detrimental to fish health; for ex-ample, trout raised at high densities can develop eroded fins.73 Researchers regularly experiment with densities to ensure optimum health and productivity.

Algae growing in tubes in RAS at COMB facility.Photo courtesy of Dr. Yonathan Zohar at UMBI Center Of Marine Biotechnology


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Specific Commercial Case Studies

Premier Organic FarmsPremier Organic Farms combines organic growing prac-tices in controlled ecological environments as the basis for their state-of-the-art, eco-friendly aquaponics farm-ing operation, which can run anywhere in the world.74 The company has done extensive research and develop-ment over the past three years on its design known as the “Pod Growing Unit.”75 Premier raises tilapia in RAS facilities that are linked to plant tanks producing but-ter and Boston lettuce, herbs, peppers and tomatoes as its core products.76 Premier Tilapia is fed an all-natural, nutritionally balanced diet of organic grain and pro-tein.77 Premier Organic Farms does not use antibiotics or chemicals.78 Nor does it use hormones.79 Other farms use certain hormones to convert female fish to males (to avoid unintentional breeding in grow out tanks before the sex of each fish can be identified).80 Premier plans to build commercial Pod Growing Units near strategic markets across the United States over the next five years, with further expansion worldwide as demand dictates. One “Pod” is predicted to produce $43 million in rev-enue annually from all segments (tilapia and mixed organic produce).81

Premier’s growing system uses 80 percent less water than conventional agriculture.82 The company’s goals are to produce high quality, safe food while achieving a carbon neutral footprint.

Marvesta Shrimp FarmsMarvesta Shrimp Farms, located in Hurlock, Maryland, is growing saltwater shrimp miles away from the coast. Water from the Atlantic is brought in and filtered down to below 50 microns and run through an ultraviolet filter (which removes unwanted bacteria, algae and viruses).83 Co-founder Scott Fritze says that the water is 100 per-cent recirculating and completely bio-secure, with no effluent and little waste. The nitrification system that they have in place now is entirely indoors and produces some feed for the shrimp within the tanks. The small amount of waste produced by the system is composed of undigested protein, and can be easily dried out and dis-posed of.84 Marvesta does not use antibiotics, hormones, pesticides or chemicals of any kind.

Blue Ridge AquacultureBlue Ridge Aquaculture, established in 1993, pro-duces RAS tilapia at their headquarters in Martinsville, Virginia. The 80,000 square foot facility produces four million pounds of tilapia a year. 85 An estimated 75,000 pounds of live tilapia are shipped to market each week from the facility, making Blue Ridge the world’s largest indoor producer of tilapia.86 Blue Ridge Aquaculture as-serts that its products are free of growth hormones, pes-ticides, antibiotics, and synthetic chemicals.87 According to the company’s president, Bill Martin, Blue Ridge Aquaculture is one of few tilapia farms that hand select broodstock for desirable characteristics, rather than us-ing hormones.88

Blue Ridge is partnering with feed production com-pany Marical and Virginia Tech to research low-salinity technology and feed options for cobia in RAS.89 The company hopes to research other marine species once they have brought the cobia production up to commer-cial levels.90 Blue Ridge is also partnering with Virginia Tech on a 30,000-square-foot RAS facility dedicated to shrimp production.91 The aim is to bring shrimp produc-tion up to 325 million pounds per year.92 In 2007, Blue Ridge began a joint venture with aquaculture company West Virginia Aqua, to produce over 300,000 pounds of Atlantic salmon and rainbow trout in RAS.93

Computer rendering of the 4,800 L/min water recirculating system at the Conservation Fund Freshwater Institute.

Summerfelt, S.T., Sharrer, M.J., Hollis, J., Gleason, L.E., Summerfelt,S. R. 2004. Dissolved ozone destruction using ultraviolet irradiation ina recirculating salmonid culture system. Aquacultural Engineering 32,

209-224. Drawing courtesy of Marine Biotech Inc. (Beverly, MA).


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ConclusionConsumers love seafood, and with wild fish stocks de-pleted, aquaculture is likely to be supplying increasing amounts of fish for food. However, not all fish farming methods are equal. In order to ensure safer and more sustainable seafood, consumers are more regularly ask-ing about how their fish was produced before making seafood choices. Common forms of aquaculture, such as open-water systems, can pollute the marine environ-ment with chemicals and waste, and may produce sea-food contaminated with pesticides and antibiotics. These are not acceptable factors for most consumers seeking greener, more healthful options.

RAS, on the other hand, are closed, controlled, bio-secure systems. Since RAS retain and treat water within the system, they reduce waste discharges and the need for chemicals and antibiotics. RAS can be efficient in production and space usage and can range from small-scale to commercial operations — growing a variety of different fish and plants.

RAS are currently operating in the United States. In fact, RAS have been under development for over 30 years, refining techniques and methods to increase pro-duction, profitability and environmental sustainability. 94 Academic, government and business facilities across the country are conducting research and further improving and expanding RAS. Premier Organic Farms, Marvesta Shrimp Farms and Blue Ridge Aquaculture, highlighted

in this report, are just a few examples of successful com-panies that are producing RAS seafood.

Technical innovations are essential for the continued growth of the aquaculture sector. Instead of pushing OOA, which can damage the marine environment and may pose a threat to consumer health, the U.S. govern-ment needs to play a vital role in promoting opportuni-ties to develop cleaner, greener, safer aquaculture in the United States, such as RAS. 95

RecommendationsFederal and State governments should increase funding to RAS researchers to help provide consumers with a cleaner, greener, safer seafood aquaculture option.

If standards must be set for an organic label for fish, RAS raised fish should viewed as the only true option, due to the controlled, closed-loop nature of RAS.

Consumers should ask grocery stores and restaurant managers whether the seafood they sell comes from domestic RAS farms. If not, they should request U.S. RAS-produced seafood as an alternative to imported, open-water farmed fish.

Fish waste being distributed by a manure spreader Summerfelt, S.T. and B.J. Vinci. (2008). Better management practices for recirculating systems. Pages 389-426 in C.S. Tucker

and J.A. Hargreaves (editors), Environmental Best Management Practices for Aquaculture. Blackwell Publishing: Ames, Iowa


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Endnotes

1 Fishwatch.gov2 FAO Fisheries and Aquaculture Department, Food and

Agriculture Organization of the United Nations. “The State of World Fisheries and Aquaculture 2008” Rome, Italy. 2009 at 16.

3 Timmons, M.B. and J.M. Ebeling. (2007) “Recirculating Aquaculture.” Cayuga Aqua Ventures at 3.

4 Timmons at 30.5 Timmons at 6.6 Timmons at 1.7 Rakocy, James. “The UVI Aquaponic System.” Clean, Green,

Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

8 Tyson, R.V. et al, “Effect of Water pH on Yield and Nutritional Status of Greenhouse Cucumber Grown in Recirculating Hydroponics.” Journal of Plant Nutrition 31.11 (2008): 2019

9 Ibid.10 Metaxa, E., et al, “High rate algal pond treatment for water reuse

in a marine fish recirculation system: Water purification and fish health.” Aquaculture 252 (2005).

11 Pagand, P. et al, “The use of high rate algal ponds for the treat-ment of marine effluent from a recirculating fish rearing system.” Aquaculture Research 31 (2000).

12 Timmons at 62113 Timmons at 620.14 Torsten, E.I. Wik, et al. “Integrated dynamic aquaculture and

wastewater treatment modeling for recirculating aquaculture systems.” Aquaculture. 287. 2009 at 361-370.

16 Timmons at 7.17 Zohar, Yonathan. “Environmentally compatible, recirculated

marine aquaculture: addressing the critical issues.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

18 Conversion of information from hectares to acres by Food & Water Watch from: Moss, Shawn. “An integrated approach to sustainable shrimp aquaculture in the U.S.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009. Samocha, Tzachi. “Overview of some sustainable, super-intensive micro-bial biofloc-rich shrimp production systems used by Gulf Coast Research Lab, Waddell Mariculture Center and AgriLife Research Mariculture Lab.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

19 Timmons at 39.20 Timmons at 47.21 Timmons at 88.22 Timmons at 88.23 Timmons at 90.24 Timmons at 89.25 Timmons at 412.26 Timmons at 413.27 Timmons at 413.28 Timmons at 413-426.29 Timmons at 50.30 Timmons at 51.31 Timmons at 51.32 Lee, Richard. “Rapid growth of black sea bass Centropristis stria-

ta in recirculating systems with geothermal cooling, solar heating, tilapia diet and microbial mat/seaweed filter.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

33 Lee, Richard. “Rapid growth of black sea bass Centropristis stria-ta in recirculating systems with geothermal cooling, solar heating, tilapia diet and microbial mat/seaweed filter.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

34 Neori, Amir, et al, “Biogeochemical processes in intensive zero-effluent marine fishculture with recirculating aerobic and anaerobic biofilters.” Journal of Experimental Marine Biology and Ecology 349 (2007): 241.

35 Tyson, et al, “Effect of Water pH on Yield,” 2019.36 Timmons at 56.37 Timmons at 57.38 Timmons at 115.39 Timmons at 53.40 Timmons at 275.41 Timmons at 54.42 Timmons at 54.43 Timmons at 55.44 Timmons at 275.45 Timmons at 277.46 Timmons at 281-283.47 Timmons at 56.48 Timmons at 275.49 Summerfelt, Steven T., et al., “Evaluation of full-scale carbon

dioxide stripping columns in a coldwater recirculating system.” Aquacultural Engineering 28 (2003).

50 Summerfelt, Steven T., et al, “Oxygenation and carbon dioxide control in water reuse systems.” Aquacultural Engineering 22 (2000).

51 Summerfelt, et al, “Evaluation of full-scale carbon dioxide strip-ping columns,” 2003.

52 Summerfelt, et al, “Oxygenation and carbon dioxide control,” 2000.

53 Timmons at 10.54 Zohar, Yonathan. “Environmentally compatible, recirculated

marine aquaculture: addressing the critical issues.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

55 Schreibman, Martin. “Urban Aquaculture: The promises and constraints.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

56 Schreibman, Martin. “Urban Aquaculture: The promises and constraints.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

57 Rakocy, James. “The UVI Aquaponic System.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

58 Food & Water Watch staff email exchange with Dr. James Rakocy, University of the Virgin Islands. June 22 – September 7, 2009.

59 Steve Craig and other from the Summit60 Kidd, Karen. “Effects of Synthetic Estrogen on Aquatic

Population: A Whole Ecosystem Study,” Freshwater Institute, Fisheries and Oceans Canada.

61 “Adoption of Genetically Engineered Crops in the U.S.: Soybean Varieties.” Data Set, Economic Research Service, United States Department of Agriculture. www.ers.usda.gov/Data/BiotechCrops/ExtentofAdoptionTable3.htm

62 Timmons at 621


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63 Timmons at 620.64 Timmons at 648-649.65 “General Discussion.” Clean, Green, Sustainable Recirculating

Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

66 Pfeiffer, Tim. “Utilization of Low-head Technology for Inland Marine Recirculating Aquaculture Systems.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

67 Zohar, Yonathan. “Environmentally compatible, recirculated marine aquaculture: addressing the critical issues.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

68 Fuller, R.J., “Solar heating systems for recirculation aquaculture.” Aquacultural Engineering 36 (2007).

69 Qin, Gang., et al, “Aquaculture wastewater treatment and reuse by wind-drive reverse osmosis membrane technology: A pilot study on Coconut Island, Hawaii.” Aquacultural Engineering 32 (2005).

70 Lee, Richard. “Rapid growth of black sea bass Centropristis stria-ta in recirculating systems with geothermal cooling, solar heating, tilapia diet and microbial mat/seaweed filter.” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

Craig, Steve. “Sustainable Aquafeeds for Cobia” Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

Clean, Green, Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

71 Timmons at 85.72 Timmons at 120.73 Timmons at 120.74 Susan Bedwell. “Premier Organic Farms.” Clean, Green,

Sustainable Recirculating Aquaculture Summit. Washington D.C.: hosted by Food and Water Watch. January 2009.

75 Bedwell, Susan. Personal email. Chief Financial Officer of Premier Organic Farms, May 15, 2009. Email on file at Food & Water Watch.

76 Ibid.77 Ibid.78 Ibid.79 Ibid.80 Ibid.81 Ibid.82 Ibid.83 “Process.” Marvesta Shrimp Farms. Accessed on May 2, 2009.

Available at: http://www.marvesta.com/process.php84 Fritze, Scott. Personal Interview. Cofounder and owner of

Marvesta Shrimp Farms, March 28, 2008. 85 Gardner, Martin. Personal email. Director of Marketing at Blue

Ridge Aquaculture, May 22, 2009. Email on file at Food & Water Watch.Nicholls, Walter. “Two sides to every tilapia.” Washington Post, August 8, 2007.

86 Ibid.87 “Tilapia.” BlueRidge Aquaculture. Accessed on May 13,

2009. Available at: www.blueridgeaquaculture.com/tilapia.cfm“Tilapia.” Op. cit.

88 Martin, Bill. Personal Interview. President of BlueRidge Aquaculture, March 26, 2008. On file at Food & Water Watch

89 Gardner, Martin. Op cit.90 Gardner, Martin. Op cit.91 Gardner, Martin. Op cit.92 Gardner, Martin. Op cit.93 Gardner, Martin. Op cit.94 Timmons, M.B. and J.M. Ebeling. “Recirculating Aquaculture.” A

at 1.95 FAO Fisheries and Aquaculture Department, Food and

Agriculture Organization of the United Nations. “The State of World Fisheries and Aquaculture 2008” Rome, Italy. 2009 at 161.

Documents

About Food & Water Watch · 2017. 4. 5. · of aquaculture; recirculating aquaculture systems (RAS), coastal ponds and open-water net pens are a few major types. Open-water aquaculture