Pacific island trials closed-loop aquaponics

2nd April, 2013 by Anonymous

Rarotonga, the largest of the Cook Islands, is combining aquaculture with hydroponics in a pilot project funded by the New Zealand Aid Programme.

Aquaponics could hold the answer to food supply for islands in the Pacific. Many lack suitable soil for growing crops, have limited freshwater, and struggle to import fresh produce because of rising fuel costs. Moreover, a recent study by the marine conservation and advocacy group Oceana named the Cook Islands the country most at risk of food insecurity through ocean acidification, which threatens its fish stocks.

Now, Rarotonga, the largest of the Cook Islands, is trialling a new aquaponic farm which combines aquaculture (raising fish in tanks) with hydroponics (cultivating plants without soil) in symbiosis. In this carbon-neutral ‘closed-loop’ system, nitrate-rich water from the fish tanks irrigate vegetables in nearby beds. The fish waste nourishes the plants; they in turn filter and oxygenate the water before it returns to the tanks. No herbicides, pesticides or hormones are used, and the system uses just 10% of the water required by traditional agriculture.

The pilot project, Te Raurau o te Kaingavai (or ‘Green Living Waters Garden’), has received a NZ$250,000 grant from the New Zealand Aid [NZAid] Programme. Analysis by the University of Auckland predicts a payback period of just 2.3 years. The Cook Islands’ Agriculture Minister Kiriau Turepu says: “Aquaculture is the way forward for us. Commercially, we can use this system to offset our import substitutions.”

Wilson Lennard of Aquaponic Solutions in Australia spent three months establishing the pilot, which is housed in a 200 square metre shed, with three systems of different size. The largest has a 50sqm growing area, which Lennard says can produce the harvest equivalent of 250sqm of soil.

Helen Ellis of NZAid expressed her confidence that this model has successful applications within “the home, the community and the commercial sectors”. If success can be demonstrated, NZAid plans to sponsor further aquaponic farms in the northern Cook Islands.

According to Professor Tim Benton, UK Champion for Global Food Security, “Solutions such as this definitely have a future in resource-stretched situations. Such systems, if properly managed, can produce very high yields relative to conventional farming – especially precious when land is limited. They must have a role in local production within cities, for example.”

Berlin is one city taking the plunge: Efficient City Farming is currently building a 1,000sqm aquaponic farm on the roof of a disused factory. – Christina Madden

Photos: iStockphoto/thinkstock

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