The Frosty Fish: A vision for the future of urban farming

I’m sitting in a cafe, sipping a cup of tea and enjoying the tastiest crème brulee I’ve ever had. Or maybe I just think it’s the tastiest. It could be the atmosphere, the tropical flowers in bloom, the sound of trickling water from the fountain, or that intoxicating euphoria that comes with being surrounded by so many plants pumping up the O2 levels. Whatever the case, in that moment I am completely happy, at ease with the world around me and my place in it. Yes, outside the temp has dipped once again into the negatives and a crust of hard, wind battered snow layers over everything. But that makes this place, the cafe Patrick’s inside the Bachman’s on Lyndale, all the more lovely. It’s a temporary respite from the literal harsh realities of Minnesota’s winters (and sometimes springs). But I think it could be even better.

Perhaps it was my contentment in that place that allowed me the chance to dream beyond that absolutely wonderful atmosphere, to a place that could be even better in every way. Over the years I have assembled the family of ideas and skills I believe necessary to build upon the Patrick’s model to make something more holistic, multi-functional, and productive. What I have come up with is part cafe, part conservatory, part urban farm, and part community art space. My working title for this business is “The Frosty Fish”, you’ll see in a minute why.

To explore these ideas, I invite you to join me on a tour the imagination. You swing open the sturdy doors of The Frosty Fish, winter hisses and whistles as you shut it out behind you. After taking a moment to stamp the last of its residue from your boots, you make your way past the community bulletin board with all its exhortations to join or attend various group meetings and cultural events, and into the main hall. Familiar scents of coffee and fresh baked bread mingle in the air with newer scents of the komboucha bar, with its dozens of varieties on tap. The line is a bit longer than you would have liked, but when you grab a menu from the box at the end of the line and take a glance you are glad to have the extra time to ponder things. Alongside more familiar fare like paninis and pastries are ethnic dishes you are less familiar with. The menu informs you that the workers, who also collectively own the business as a cooperative, decided they wanted at least one dish from each of the cultures in the neighborhood, to make it more inviting to the people who already live here. Looking around, this strategy seems to be working because a much greater diversity of people than, say, your average Starbucks, is assembled here.

When you make it to the front of the line, you decide to order the fish and chips with microgreen side salad. Aside from the batter and a bit of salt, everything in your meal was produced right on site in the greenhouse attached to the cafe. Eager to see this greenhouse you have heard so much about, you take your number and head out to the greenhouse patio area. Before you even get there you are met with the warm, humid, tropical breath of green growing things.

Upon arrival you are overcome with the sheer immensity of the operation. A two acre pond dominates the massive, multistory greenhouse.

Giant waterwheels scoop bucket after bucket of water up to the top of an apparatus of grow beds, situated above the pond and stacked tier after tier above each other, absolutely bursting to overflow with vegetation. You can see now how the cafe can manage to produce so much of the food it sells. Workers move gracefully on the apparatus to harvest the food, depositing it into baskets on their backs. A chorus of brightly plumed birds who make their home here serenade and entertain you while you dine. Occasionally a worker throws a handful of food into the pond, the resulting churn of fish indicating much more happening below the otherwise calm surface of the water. There is a permanent stage adjacent to the patio, facing the rest of the greenhouse. The blooms of the passionflower vines twining up the support scaffolding are on full display.

After lunch, the sunlight still streaming strongly on you through the greenhouse glass, you decide to join a tour that is just forming up. Your guide explains that this farm is unique in that it functions more like an ecosystem, with waste from one part feeding the growth of another. The pond and grow beds are what is called an aquaponics system. Without the plants, the fish would dirty their water to the point of toxicity very quickly. Instead the water wheels, driven directly by the mechanical action of small wind turbines on the roof, scoop up the water to the top of the stacked grow beds. The water is dumped into the front end of the grow beds, which are filled with gravel. The gravel acts as a host for bacteria which convert the fish waste into a form the plants can take up through their roots as food and the water returns to the pond cleaned.

The plants are grown in clay pots in a medium of compressed clay balls called hydroton. This allows the water level to rise and fall quickly, increasing the productive capacity of the plants. Also, because the fish waste never touches the parts of the plants that are eaten, there is a much lower risk of contaminating them with pathogens. The spaces between the round pots allow a cleanup crew of critters to live, such as crabs and freshwater shrimp. They eat any algae or detritus that might otherwise build up with so much water circulating.

The grow beds themselves are made of wood and sealed much as wine barrels are,  by the pressure of the wood swelling with water, each plank pushing against its neighbor to form a watertight seal. This eliminates the need for plastics common in other aquaponics operations, which can leech into the water and ultimately the food.

Another benefit to the grow beds being basically islands on scaffolding above the pond is it puts them off limits to pests that cannot swim or fly. The food plants and the flowers and other food plants planted around the perimeter of pond also serve as insectaries that host predatory insects that keep pests in check. This ecosystem-style approach keeps things well enough in check to eliminate the need for pesticides, while also not requiring the almost laboratory-sterile environment needed for other indoor operations.

“The ecosystem model doesn’t stop there, though,” says the tour guide, indicating the dense stand of mangrove in the center of the pond. You learn that though mangrove is often found in brackish water, it does just fine in fresh water. In nature, the tangled thicket of buttressing roots of the mangrove serve as a kind of nursery to all sorts of life. Here they do the same and the tilapia, catfish, crabs, shrimp, even the bizarre giant freshwater prawns (re-branded as “Prairie Lobster” in the cafe), all use the mangrove roots to shelter their young. Snails, birds, and a whole host of other life make their home in the greenhouse’s mangrove as well.

Even the uneaten food from the cafe never goes to waste. You are led into a screened in portion of the greenhouse and immediately hear buzzing from the bushes. You are taken aback at first to learn that the food waste from the cafe is fed to compost worms and the larvae of a fly called the Black Soldier Fly. It’s a strange concept to get used to, bugs and worms being encouraged to eat food waste. But you are relieved to learn that the adult, fly form of the Black Soldier Fly doesn’t even eat, it just mates, lays eggs, and dies, so there is no vector for disease transfer like there is with houseflies. Its larval form is, however, a voracious eater, capable of going through bone, shell, meat, dairy; almost anything you can throw at it. Its huge appetite also fuels a huge metabolism and the heat it gives off while eating goes towards heating the greenhouse in the winter. It also happens to make a fat and protein rich food for the fish, who are fed almost entirely by the larvae and other foods grown on site from food waste.

The Frosty Fish has also worked out a deal with the laundromat next door to route the dryer vents through the greenhouse to the outside, siphoning off a large portion of the heat in the process. That, combined with the hot composting that also takes place in the greenhouse, as well as the pond acting as a heat sink and reflective insulation being pulled across the whole greenhouse, just under the roof, at night, means no extra heating is needed in the winter, saving a lot in materials and energy.

The sun is also the only source of light for the plants and wintertime crops are selected based on being suited to wintertime light conditions. This eliminates the cost and energy footprint that other indoor growing operations can struggle with.

Altogether, your guide informs you, the greenhouse produces over 1 million pounds of food a year, including over 10,000 fish dinners. Even the water for the pond mostly comes from what falls on the greenhouse roof, which is then collected in tanks, filtered, and fed into ponds. This, combined with the stacked grow beds over the pond and the very low energy needs, the recirculation of waste, having no need for farm machinery, and ability to operate year round, make the operation much more productive per acre at a much lower energy and materials cost than any other type of farming. It is a good fit for the city. “Don’t get me wrong,” your tour guide clarifies, “community gardens are great and they serve a vital role in the neighborhoods they inhabit. But when it comes to having food production at the forefront of the operation, what is needed in cities is a form that uses an economy of space, energy, and resources, can produce year-round, and can serve multiple secondary roles. This greenhouse not only produces a whole lot of food on a meager budget of resources, but it serves as a space to help better connect city dwellers to the food they eat. And it’s a community gathering space, not only for cafe patrons, but for attendees of all the art shows, concerts, and movies we put on in the patio and stage area. In fact, we have a local act performing here tonight and tour participants get a discount, if any of you are interested. It is quite the experience to listen to music surrounded by so much. . . life, especially in the dead of winter.”

That concludes our tour, dear reader. It is my great hope that at least some of the ideas presented here have sparked something in you to envision with me a new path for urban agriculture and all the possible add-ons that could go with it.