Aquaponics project takes root in Minnesota

Water is important for both farmers and brewmasters.  So it seems fitting that two historic breweries in Saint Paul Minnesota, have been retrofitted into perhaps the largest and most advanced aquaponics operations in the country, to combine the farming of fish and vegetables.

Urban Organics (UO), a local company in St Paul, has been producing tilapia and hybrid striped bass together with high-value produce, in the former Hamms brewery building since 2014.  “After seeing a news story featuring an urban farm in Milwaukee, Wisconsin using aquaponics as a method for indoor farming, we hatched the idea to build and operate an indoor fish and produce farm in the heart of the city,” says David Haider, one of the company’s founders.

In November, they took delivery of their first batch of Arctic charr eggs at the newly renovated Schmidt brewery, only a few blocks away.  Haider will be the manager of that facility.

They are good sites, says Marc Turano, global sales manager for Pentair Aquatic Eco-Systems. The company has a unique partnership with both projects, a separate entity known as Urban Organics Pentair Group. “They source water from an aquifer below the city,” says Turano.  The wells are between 350- and 400-ft deep. At 10C that’s a bit cool for the tilapia and hybrid striped bass they have been growing at the Hamms site, but it’s perfect for the salmonids they plan to raise at Schmidt.”

Turano says that the thick brewery walls help keep heating costs down, adding that the retrofits “did not present an overwhelming challenge.”  Pentair supplied the RAS systems for the fish and consults with Urban Organics on the operations of the system.

“Our original Hamms site is relatively small at 8700 sq feet,” says Haider.  “There are just four 3,000-gal poly tanks, but with careful planning we were able to harvest on a weekly basis.”  Urban Organics started off raising tilapia, but have switched to higher value hybrid striped bass.

“What makes both of these projects different from most aquaponics systems is that each is designed to be a decoupled system,” explains Turano.  “You can run the fish production system separately from the plant production system, closing a couple of valves.” 

Traditional aquaponics models often operate on a ratio of 7 parts plants to 1 part fish, Turano comments.   “This model we have gone with gives a more diversified cash flow.  We can maximize production of fish and maximize production of plants.   We are not trying to create a balanced environment to manage nutrient loads.”

Supplying the local market

The fish production side of the system is basically the RAS system that Pentair uses, Turano explains. Water from the tanks is first filtered mechanically through swirl separators to take some of the solids off the bottom. The water then goes to a mechanical drum screen filter to remove some of the larger solids and then to a bio reactor.  The wastewater can then be pumped back to the tanks through UV filters, or sent over to the plants.

Turano says the project sits somewhere between a stand-alone RAS system and traditional full-loop aquaponics.  “We get less waste than regular RAS, but more than traditional aquaponics,” he points out.   “The waste is an added cost, but we also get more high-value fish.”   They are looking at ways to reutilize the wastes.

The hybrid striped bass grow from 5 grams to a market size of 1.5  to 2 lbs in less than a year.  A food conversion ratio of 1.3 to 1.5 is achieved on a diet of 40-percent protein, 10-percent fat, delivered by belt feeders. The feeders give a more continual supply of nutrients to the plants, to the fish and to the bio filter than hand feeding, Turano points out.  “Frankly I’ve never see hybrids grow as fast as they were able to grow them.”  

Three levels of shelves hold six-inch water trays with floating styrofoam containers for the plants.  Breweries don’t need windows, so all the light comes from LEDs and fluorescents.  Basil, micro greens, kale, chard, lettuce, parsley and cilantro have all been grown depending on the needs and wants of the local market.

That’s all part of the urban farming story Haider points out.  “We can produce fresh food in urban areas where there is no local source of fish and vegetables and produce year-round in regions like Minnesota, with a short growing season.”  The USDA-certified organic greens and high-value fish raised with minimal inputs in the RAS system appeal to educated consumers in the area. 

Haider says there is not much aquaculture in Minnesota, mostly hatcheries for bait and stocking purposes.  “We believe the demand for commercial aquaculture will increase as we look for more sustainable systems of food production,” he says.   Working closely with the Minnesota Department of Natural Resources ensured Urban Organics a smooth approval process for their commercial aquaculture license.

“Why not Saint Paul?” Haider quips. “We love our city! We live here, we are raising our family here.  It’s great to contribute to the diversity of our city.”

Schmidt facility

The Schmidt build expands on that initial success.  “We were able to learn so much from the Hamms facility,” comments Turano.  At 87,000 sq feet, it’s the size of 31 tennis courts combined, and will be one of the largest aquaponics systems in the world.

The larger scale allows for fluctuations in pricing and management and increases the profitability.  “Small scale is one of the difficulties across the spectrum of aquaponics,” Turano says.

The tanks and filtration systems are all installed at the Schmidt facility, while they finish erecting the plant racks.  “They decided to put in a small hatchery and have brought in both eggs and fry for the Arctic charr,” says Turano.   “They can select how they can do it and they saw an opportunity to hatch.”  There are quarantine, hatchery, and nursery tanks as well as grow-out tanks. 

Haider says they moved into Arctic charr due to market demand. “We work closely with our fish processor and distributor to determine the best species to fit current markets and our farms.”  He says they are also considering Atlantic salmon.  Production targets are 275,000 lbs of fish and 400,000 lbs of produce a year.

Pentair is not looking to own farms long term, says Turano.  “What we are hoping is that this will stimulate the growth of the model and others will replicate that.”

“The reason for Pentair’s involvement in the project is to prove the financial validity.  We believe that it can be a profitable model and that is what we are trying to prove.”

— Tom Walker