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Seawater Agriculture: High-tech and Low-tech paths

Posted in Movements, Research by Kate Archdeacon on December 3rd, 2012

Source: guardian.co.uk


Image from Seawater Greenhouse

In the Guardian this week, there’s an article by Jonathan Margolis about the commercialisation of a technology that uses seawater as the main element of agriculturally productive greenhouses.  Much of the article focuses on the way the technology, developed by British theatre lighting engineer Charlie Paton, has been scaled up and combined with extra technology to provide consistent, commercial-quality crops from the Sundrop Farms greenhouse in the desert outside Port Augusta, in South Australia.  On it’s own, that’s pretty exciting and well worth a read.

A 75m line of motorised parabolic mirrors that follow the sun all day focuses its heat on a pipe containing a sealed-in supply of oil. The hot oil in turn heats nearby tanks of seawater pumped up from a few metres below ground – the shore is only 100m away. The oil brings the seawater up to 160C and steam from this drives turbines providing electricity. Some of the hot water from the process heats the greenhouse through the cold desert nights, while the rest is fed into a desalination plant that produces the 10,000 litres of fresh water a day needed to keep the plants happy. The water the grower gets is pure and ready for the perfect mix of nutrients to be added. The air in the greenhouse is kept humid and cool by trickling water over a wall of honeycombed cardboard evaporative pads through which air is driven by wind and fans. The system is hi-tech all the way; the greenhouse is in a remote spot, but the grower, a hyper-enthusiastic 27-year-old Canadian, Dave Pratt, can rather delightfully control all the growing conditions for his tonnes of crops from an iPhone app if he’s out on the town – or even home in Ontario.

The remainder of the article touches on the divergence of philosophy between Paton’s Seawater Greenhouse, and SunDrop.

The Seawater Greenhouse method, which they are still promoting actively, involves no desalination plant, no gleaming solar mirrors and little by way of anything electronic. Everything in the Seawater Greenhouse vision is low-tech, cheap to start up and reliant on the subtle, gentle interaction of evaporation and condensation of seawater with wind, both natural and artificial, blown by fans powered by solar panels. If things go wrong and production is disrupted by a glitch in this model, you just persuade people to eat perfectly good but odd-looking produce – or harvest less and stand firm by your sustainable principles.

For those of us interested in the gap between local, low-tech production designed to shift society away from BAU, and the changes that occur when those systems scale up to cater to the existing market, this article may also provide a few points of contention.

Read the full article by Jonathan Margolis for the Guardian.

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