Quick Dips

Energy Efficient Prawns

Raising tropical prawns in the middle of the North Island might sound like an unlikely venture, but Aquatech Farms, working with Taupo Electricity, have come up with a number of cunning ideas to make it practical.

By passing warm water from the Wairakei Power Station through a heat exchanger, they can keep their nursery and production ponds at a nicely tropical 28^oC using only a hundredth as much electricity as would otherwise be required, and utilising an energy resource otherwise wasted.

Another innovation is an ammonia filter which consists of 17,000 ping-pong balls in a rotating drum. These provide a large surface area for ammonia-consuming bacteria to grow on.

Genetic engineering is used to increase yields. A male prawn can be converted to a female by removing its gonads, and can then be crossed with a hybrid male to produce all-male eggs. The resulting prawns grow bigger and faster than normal, enabling harvesting of three crops each year instead of the normal two.

The energy efficient system was a finalist in the 1992 ECNZ Rutherford Awards for innovation in energy efficiency.