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  Aquaponics as an
example of a sustainable
and holistic perspective
or Is this the making of
a sewage revolution?

Aquaponics

Aquaponics is the combination of fish farming (aquaculture) and soil-less vegetable growing (hydroponics). An ideal system for intensive food production in small spaces in the city.

Aquaponics is, to put it simply, an aquarium, connected to a soil-less vegetable bed. The water is pumped from the aquarium to the plants, that can take up the nutrients that bacteria convert from ammonia from the fish, into nitrite that plants can take up. And the fish get cleaned water back from the plants. Win-win. It is no small amount of nutrients that the plants get: from each kilo of fish that is produced, 6-12 kilos of vegetables can be produced!

Using available space in the city for food production saves energy for transports, gives us fresher vegetables, gives fulfillment for the grower, and in some cases even a green paying job. It can also have great educational values. In some parts of the city there is ground space enough, such as parks and gardens, but also the more dense neighbourhoods can be cultivated if we grow vertically. Walls, balconies and roofs can become vegetable patches too.

From my perspective, as a roof gardener, one of the main challenges is to keep the weight low. Many buildings may support a lightweight green roof, usually a sedum vegetation, even if they weren’t built for the purpouse or reinforced. A sedum roof can weigh as little as 50 kilos per square metre, when wet. But for growing vegetables, you would normally need at least 20 cm soil deapth, and that is too heavy for most roofs. If we were to use only new buildings for greenery, that would be a very small percentage of the city’s roof space.

Therefore, hydroponics is a good solution, because without soil, we can avoid a lot of unnecessary weight. In a hydroponic system, the plants’ roots grow in some porous material, such as pumice or leca, or even hanging into water without substrate. For example, you could use a long plastic pipe, laying near to horisontally, with holes to place the plants in. Water is recirculated through the pipe with a pump. In conventional hydroponic farming, such as in greenhouses, most of the time a chemical fertilizer is added to the water. I do not consider chemical fertilizers as something that belongs in sustainable food production.
(Here’s why.)

 

   

 

    [2012-02-07]
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