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How to grow lettuce and fish indoors, all year long

Chris Julin Sep 10, 2014
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Tony Beran is standing in the kitchen at the Lake Avenue Restaurant in Duluth, Minnesota, with a head of romaine lettuce in one hand and a clump of curly lettuce in the other. 

“They’re beautiful,” he says.

Beran’s the executive chef, and one thing he likes about these bunches of lettuce is how clean they are. “They’re grown aquaponically instead of in dirt,” he says. “Which is wonderful in the kitchen. It’s less labor for us.”

Another thing he likes about this lettuce is that it was grown just up the road. The restaurant features local ingredients, and Beran serves locally grown lettuce all year, which is a bit of a trick in a place like Duluth. Last winter, the temperature was below zero 23 days in a row.

But it’s always warm in the greenhouse at Victus Farms, where Beran’s lettuce came from. It’s about an hour’s drive from Duluth in a little mining town called Silver Bay.

“These are all our babies,” says Mike Mageau, as he shows off his latest lettuce crop. He runs the place, and he’s an unlikely looking farmer. He’s wearing cargo shorts and a backwards ball cap and he’s barefoot. He’s an unlikely looking professor, too, but that’s his job: professor of geography at the University of Minnesota Duluth. He runs a program in environment and sustainability, and this indoor farm is a research project.

Universities and private businesses across the country are experimenting with aquaponics.

“It’s kind of fun,” Mageau says. “It’s like the electric car. It’s almost a race to come up with the method or the model that really works well.”

Most of Mageau’s lettuce is floating. Each plant is stuck into a hole in an inch-and-a-half-thick sheet of polystyrene foam. The foam rafts float in pools in the greenhouse, and the lettuce roots dangle through the foam into the water.

The fish live in a neighboring room. They’re tilapia, and they swim in nine round plastic tanks, each one about six feet tall. Waste from the fish gets pumped over to fertilize the plants in the greenhouse, and some of the pools in the greenhouse grow algae and duckweed that come back into this room to feed the fish. 

“Which means you grow fish and plants sort of in concert, one living off the other,” Mageau says.

Two years into the project, Victus Farms sells all the fish and vegetables it can produce to local restaurants and stores. Now the goal is to get more efficient.

Mageau and his crew built floor-to-ceiling racks made of PVC pipe, an idea they got online and spent six months refining. Each rack looks sort of like a ladder. On the horizontal pipes, they drill holes in the top and stick a plant in each hole. Then they run nutrient-rich water from the fish tanks through the pipes, bathing the roots of the plants.

“It’s all trial and error,” Mageau says. “You know, ‘I wonder if we can grow tomatoes in four-inch pipe?’ Yes! You try it, and it works! I mean, look at these tomatoes, there’s millions of them.”

One wall of the greenhouse is covered with ripening tomatoes and strawberries growing out of white, plastic pipes. And the fruit looks good. 

Mageau’s banking on this vertical gardening scheme for the future. It will let them make use of some of the empty vertical space, and it will allow them to move the fish into the ponds in the greenhouse, making the second room for fish unnecessary.

“Then we can grow probably 10 times the plants per unit surface area, which means our greenhouse needs to be one-tenth the size, ” Mageau says.

He wants to pilot a small, hyperefficient version of Victus. 

“Every small town could have one or two or three of them,” he says. “And the food could literally be produced in the backyard of the restaurants or whatever.”

Mageau says aquaponic operations will never replace farming in dirt, but they could give a big boost to the amount of local food that’s available, especially in places with short growing seasons.

The Victus building cost about $2 million, but Mageau thinks a self-sustaining version could be built for a small fraction of that. It really could be built in someone’s yard.

So that’s what he’s doing next.

Mageau’s right-hand man at Victus is Baylor Radtke, a former student. The two of them pooled their money and on their own they’re building a much smaller and simpler fish and vegetable operation in Radtke’s yard in Duluth.

“The whole point of it is to allow people to grow as much as we did in that $2 million facility in a facility that costs under $100,000,” Radtke says.

The cost has come out way under. Radtke and Mageau say the new operation will take only $20,000 to build because they’re doing all the labor. The annual energy costs will be comparable to a single-family house, and they’re cutting those even further with solar panels on the roof of the greenhouse.

They figure they’ll bring in $50,000 in the first year, from a building the size of a four-car garage, about 24-by-52 feet. They plan to be completely up and running by this fall. 

If it works in northern Minnesota, they say, imagine how well it could work someplace warm. Like Iowa.

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