Aquaponics: A Sustainable Solution?

By Carley Postma

A typical interaction at the local big-box home-improvement store (as I go to the plumbing aisle for my third time that week):

    The cashier sees a young woman carrying a single 10-foot PVC pipe to the
    checkout (I can understand how this is curiosity-inducing) and asks, “What
    are you working on?”

    “I’m a student intern at the university botanical gardens and arboretum building
    and eventually conducting research on an aquaponics system,” I explain, waiting
    for the inevitable next question….

    Timidly, the cashier responds, “Oh cool! ……What is aquaponics..?”

At this point it’s a question I’m used to answering. Aquaponics is a term that most people likely have never heard before. My best attempt at an explanation is the next logical sentence after uttering that I have an aquaponics internship this summer. In fact I think my father has heard me explain it to so many of our friends and family that he almost has my answer memorized. I find myself enjoying explaining it to others and getting them excited about the awesome process and complete ecosystem that is aquaponics. And yet why are so many people completely unfamiliar with the topic? It claims to be a sustainable and logical solution to the growing global food crisis. But if it is truly as great as it seems then why aren’t more people embracing this concept and why isn’t it being talked about?

Before I continue, I should explain what I’m working on as an intern at Matthaei Botanical Gardens & Nichols Arboretum. My project this summer is to help build a large aquaponics system that will be housed in Greenhouse 5 at the botanical gardens for a year while the Alfaro Lab and Sustainability Without Borders collect data about the system's energy and water usage and its parameters. (Jose Alfaro is assistant professor of practice in the School for Environment and Sustainability; Sustainability Without Borders is a student organization sponsored by the Center for Sustainable Systems at the U-M School for Environment and Sustainability.) The goal for the project is a published study examining the hard numbers of an aquaponics system and assessing the claims of sustainability that surround this concept.

So what exactly is aquaponics anyway? To put it in the words of Sylvia Bernstein, author of Aquaponic Gardening, “Aquaponics is the cultivation of plants and fish together in a constructed, recirculating ecosystem utilizing natural bacteria cycles to convert fish waste into plant nutrients.”

In other words, aquaponics is a system where plants and fish are grown together symbiotically. The fish waste is converted from ammonia into nitrates by bacteria for the plants to use as fertilizer, and the plants filter and clean the water for the fish. Aquaponics is a great way to produce both plants and protein in the same system, and all of the food grown in aquaponics systems is organic by necessity. If you add growth hormones, the plants will die and any insecticides or fertilizers will kill the fish. However, as for the claims made about its sustainability, these have been harder to prove as fact.

In theory aquaponics sounds very sustainable. It has the potential to use less water than traditional farming, less space by being grown vertically, and it doesn’t create harmful fertilizer runoff. But there hasn’t been extensive research on the sustainability and practicality of aquaponics systems—especially on a larger scale.

Researching these claims is something that we hope to accomplish by building a large aquaponics system with Sustainability Without Borders. The system we are building at Matthaei Botanical Gardens is referred to as a CHOP system—an abbreviation for Constant Height, One Pump.

Image courtesy The Aquaponic Source Inc.

  

In this system the water is pumped from a sump tank into a fish tank that is raised above the grow beds. Using gravity, the water then flows out of the fish tank to the grow beds. The water courses completely through the gravel-filled grow beds and then siphons back into the sump tank. This system keeps the water levels at the same height, and this in turn reduces the stress on the fish—much more so than a basic flood and drain aquaponics system in which the water pumps straight out of the fish tank and into the grow beds.

(Our system before any plumbing. The large black-plastic-
covered structure in the foreground is the sump tank
where water will be pumped into the raised fish tank
in the back on the far left. The water then flows into
the two tanks on the right and then drains back into the sump tank.)

Irrigation grid to distribute water evenly over the large
surface of the grow beds in its early stages 

While aquaponics may seem like an exciting and eco-friendly way to produce food, it does also have its drawbacks—as I have experienced first hand! Below is the main reason why it is nearly August as I write this and we have yet to actually put any life forms into this system: a big and persistent leak problem.

We had a leak in one of our grow beds that attributed to a
loss of about 6 in of water a day! In a 12 ft long x 4 ft wide x 2 ft
deep tank that is nearly 24 cubic feet lost daily!

The water, water temperature, and pH are all crucial to helping three different types of organisms survive and thrive in one environment. This means that a significant leak or a rise in pH of .5 can have drastic consequences on the entire system. The constant running of pumps needed to provide oxygen to the fish and keep the nutrient-rich fish water flowing into the grow beds will also hike up our energy usage. But is this still a more sustainable solution? With the construction of this system we hope to answer that question by monitoring the use of electricity and water in a large-scale aquaponics system. Our hope is to be growing peppers and tomatoes in the grow beds and raising blue tilapia fish by September! I am very hopeful that our research will be able to provide some hard numbers for exactly how eco-friendly this concept is. Either way, I am hooked on aquaponics for life!

Carley Postma, from Holly, Michigan, is a senior at the University of Michigan studying ecology and evolutionary biology with a minor in the environment. This summer she is working with Jose Alfaro and Sustainability without Borders to build, manage, and research an aquaponics system at Matthaei. Carley hopes to work in herpetology or environmental education someday. Her lifetime goal is to visit every national park. Carley’s internship is made possible by Sustainability Without Borders, a student organization sponsored by the Center for Sustainable Systems at the U-M School for Environment and Sustainability.