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Engineering water

September 27, 2011

London: It takes 17 bathtubs of water to produce one bar of chocolate, according to the Science Museum’s latest water exhibition; which seems excessive, not least because eating chocolate hardly slakes a thirst. In fact, it usually makes me reach for a glass of water – should that be counted in the bathtub analysis?

Solar concentrators are already used to distill seawater

The exhibition, Water Wars: fight the food crisis, which opened last week, is buried at the back of the museum, (handily opposite the café), in its shiny blue-glass Antenna ‘News’ Gallery. “We couldn’t use brown cracked earth or other classic drought images because they’d look bad against the blue wall. And besides, that would be a bit too Oxfamy,” explains Sarah Richardson, the exhibition manager. Instead, they’ve opted for a dark navy abstract, which is supposed to represent the majority of freshwater locked up in ice caps. Water Wars focuses on the agricultural issue: there will not be enough water to grow the world’s food because of climate change and population growth.

The water exhibition joins the Atmosphere Gallery in exploring climate science

Perhaps in a bid to avoid being too Oxfamy, the small exhibition focuses on five technological fixes for the thirsty crop problem – there’s not a drip-irrigator in sight. Instead, Richardson has chosen projects that use the power of microbes, the sun, wind and fog to water plants in arid conditions. The first is perhaps the most speculative: a microbe-powered fuel cell that powers desalination. Currently, it takes a few hours to get a teaspoon of freshwater out of the device.

The microbial fuel cell for desalination

A couple of new fog net designs were on show, one based on the Namibian toktokkie beetle, but having seen various fog harvesting projects, the issue for success is not about fractional improvements to the amount of water harvested – the standard nets provide ample water – but in keeping the system cheap enough and ensuring it’s maintained by the community.

Greenhouse in the desert using the honeycomb-wall for seawater distillation

My favourite project was a honeycomb-inspired sheet of corrugated cardboard that is used as a wall for a greenhouse. The wall is sprayed with seawater (using a solar-powered pump and spray) and the wind evaporates out the salt, leaving the humid air to condense onto the greenhouse crops. Ingenious. If there’s no wind, solar fans are activated. The system is already being used in Australia, and I reckon it would work well with hydroponic systems as soil fertility becomes more of an issue.

Biodegradable plastic planters that concentrate dew and rainwater on seedlings

This cute snapshot of engineering innovations didn’t touch on the enormous socio-political issues surrounding the global water crisis in agriculture, such as why some of the world’s driest countries are producing the thirstiest crops for export, while their domestic populations face food shortages. Nor did it look at different agricultural methods that use water more efficiently. But, the exhibit managed to make farming concerns interesting – quite an achievement. As Richardson says, they didn’t want to campaign, just to raise awareness of the issue and “tell nice inspiring stories about how science can be used creatively to help”.

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