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RAS technology offers more sustainable land-based fish farming option

By Kendra Caruso | Nov 02, 2020
Source: City of Belfast Nordic Aqafarms' proposed land-based fish farm site plan sketch.

Belfast — Maine is becoming a destination of choice for the aquaculture industry. Companies that want to build commercial land-based fish farming complexes are drawn to Maine because of its abundance of fresh water and proximity to the ocean, according to researchers in the state. The state has attracted five separate land-based fish farming companies in recent years.

 

Technological advancements in fish farming like recirculating aquaculture systems have allowed land-based facilities to become more sustainable, while giving companies more control over how the fish are grown, which produces an optimal product, academic researchers say.

Net pen farming is still the most common method of growing fish, but RAS, where most of the water used in fish tanks is recirculated, has made land-based operations more practical, according to Deborah Bouchard, director of the University of Maine’s Aquaculture Research Institute. The technology uses less water than a flow-through system, which recirculates no water, she explained.

While the majority of land-based fish farming facilities are in Europe, there is a high demand for fish like salmon and trout in U.S. markets, Bouchard said. The appeal of saving money on transportation costs by building in the U.S. has drawn companies like Norwegian-based Nordic Aquafarms to states like Maine.

Whole Oceans, based in Bucksport, presold 10 years' worth of product before it even opened its facility, said Damian Brady, assistant professor at the University of Maine’s Marine Sciences School and Aquaculture Research Institute.

Benefits and drawbacks

There are different benefits to RAS compared to net pen, according to Bouchard. Fish farming in a facility on land allows companies to precisely control feeding, water temperature and other factors for best salmon growth.

She said that in many ways, land-based fish farming saves on feeding costs and can yield a higher-quality product compared to net pen farming. But the development and electricity costs to build and run the facilities require a high upfront investment, she said.

Using RAS makes it easier to remove nitrogen and other pollutants because most of the fish and feed waste is removed in an on-site wastewater treatment plant, Brady said.

He said facilities using RAS actually have less of a “water footprint” than other types of farming, such as the beef industry. A cow consumes more water over its life than what is used in land-based fish tanks.

Bouchard said these systems are not likely to amplify water shortages in droughts. She does not think these systems are large enough to deplete Maine’s fresh groundwater. Maine is attractive because of its abundance of fresh and salt water. RAS fish farms do not extract as much groundwater as a company like Poland Springs, Brady said.

Controversy over discharge

Opponents of Nordic’s proposed land-based fish farm in Belfast have suggested that the company use a closed system that recirculates 100% of the water with no discharge. Bouchard said any RAS will always have to have some amount of outflow.

Nordic said zero discharge RAS technology is not advanced enough to perform on a commercial scale. It is proposing one of the largest land-based farms in the U.S., using a system that recirculates 99% of water in the tanks, which it says will cost about $500 million to build.

Using a closed RAS risks the water quality and fish welfare, Nordic spokesperson Marianne Naess said in an email. Aquaponics, another idea floated by opponents, only partly achieves zero discharge but requires a lot of land for agricultural production for a small amount of fish production.

Naess said Nordic’s technology filters nitrogen and other chemicals out of the water using ultrafiltration, which reduces the water need compared to other RAS technology. She said no other facility in Maine uses the ultrafiltration process that Nordic is proposing and no commercial facilities in the U.S. or Europe use zero discharge technology.

“None of the existing or proposed RAS projects in Maine are zero discharge,” she said in an email. “None of the international seafood companies have zero discharge in their smolt farms. None of the existing grow-out farms at scale in Europe have zero discharge. Zero discharge is not an option for any serious producer.”

Bouchard said using RAS on a commercial scale is still highly experimental, but technological advances are increasing. Net pen farms will continue to dominate the fish growing industry into the near future, she believes, but researchers are expected to learn a lot about RAS technology in the next five years as more land-based fish farms use it.

Editor's note: This story has been changed to correct the spelling of Deborah Bouchard's name and to remove a misattributed paraphrase.

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