Monday, March 25, 2013

Aquaponics: Towards a truly sustainable agriculture

Figure: The nutrient cycle driving an aquaculture system
Figure: The nutrient cycle driving an aquaculture system
There is something about a really good idea that grabs me. Like when I first discovered that there were urban farms, with the farmers actually making more money by operating in city limits, and selling at farmers markets.

I was intrigued. Good idea. I even thought about pursuing this as a career option since I do have a lot of experience organic gardening. And, like always, I was looking for a challenge.

But reality made me rethink things. I had just moved from CA to OH. I had been laid off twice in the past five years when the businesses I worked for shut down. So going into business for myself seemed like a great opportunity -- when I got my financial head a little bit above the water. ...

In the interim, I researched. And thus, I was in the library, pawing through Mother Earth News in January, and I found a simple article that described aquaponics. I was amazed. The system allows a person to grow fish in an aquarium, and instead of cleaning the water with an aquarium filter, the water was pumped over a hydroponics-style grow bed which filtered the water, and returned it to the fish, clean.

Sounded cool. So I did some research. It turns out that most modern aquaponics systems were conceived by engineers -- usually working at research universities -- who were trying to figure out creative ways to use the waste water produced in aquaculture, or commercial fish farming systems.

Fig 2: A Recirculating Aquaponics system (based on hydroponics)
A Recirculating Aquaponics system (based on hydroponics)
Because of these origins, at first the vegetables were just a "by product." But as commercial growers began experimenting, it became evident that it cost a lot to grow the fish. But the vegetables were another matter. Not only were they inexpensive to grow, the fish waste provided an assortment of micro-nutrients. So the word through the vine is that aquaponics tastes as good as, if not better than, soil-grown produce. With a fraction of the space, time and money.

So, right now, I am combing through the web to find some good "DIY" systems. It seems like most have a lot of "moving parts," which always troubles me. They look like a hydroponics system with a fish tank. Water is dumped from the tank into a trough filled with gravel. Plants are planted directly into this medium.

These systems are of two basic types.
1) Constant Recirculating: The growing bed is kept wet constantly, which requires the water flow to be evenly spread across the bed to avoid creating "dry areas."
2) Flood and Drain: The water fills to a certain level, causing a valve to open, allowing the water to drain. Once drained, the valve closes, and then the bed begins to fill again -- similar to how a toilet tank fills and then drains into the bowl.

These systems are "familiar" to many folks who garden using hydroponics understand how to use and maintain these systems. But they do require maintenance. The plumbing must be cleaned monthly. And things like sprayers valves and bell siphons must be kept in good working order, or the system may cease working.

Figure 3: Aquaponics system using floats.
Aquaponics system using floats. 
Due to the complexity of this type of system,  many of the commercial systems use a float system. Based on original research done during the 1970's and 80's by The New Alchemy Institute in Massachusetts,  these systems circulate water in deep troughs. On these troughs, the farmer "floats" plants on Styrofoam rafts, allowing the roots to dangle into the nutrient rich water. Which entails fewer moving parts, thus making it easier to maintain.

I am not sure if I'll ever make a go of this. I need to get my finances in order, and buy a piece of land. But it's great just to dream about. And know that, in the future, a little engineering and Yankee know-how, combined with vision and hard work can help us all eat good, clean, healthy and chemical free produce. And  give you a solid source of mercury-free fish to boot.

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