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London, United Kingdom
I am an engineering academic at University College London where I work on the sustainability of urban water systems. I am interested in the role of engineers and technology in sustainable cities.

Thursday, 13 September 2012

Why I worry about desalination

Global desalination capacity is currently growing at around 9% per year, much faster than the global economy (3.5%) and population (1.2%). Most of the growth is occurring in the Middle East North Africa region, but capacity is rapidly expanding in Israel, the US and Australia. London's first desalination plant was commissioned in 2011. The Water Corporation of Western Australia commissioned its first desalination plant in 2006 and will triple capacity to 145 billion litres per year by the end of 2012, providing a 'climate independent' source of water meeting around half the state's demand. By the end of 2013 desalination is predicted to meet 85% of Israel's domestic demand, following the construction of a 100 billion litre per year plant at Ashdod. Desalination is seen as a core element of climate change adaptation, a response to drying climates.

Discussions about the global water crisis usually begin by pointing out that only 0.01% of all the water on the planet is available for human use - 97% is saline and the rest is either frozen or inaccessible. Desalination puts an end to that. Desalination effectively makes all the liquid water on Earth available for human use, but at what cost?

The most obvious cost of desalination comes from its energy requirements. Most new desalination is based on reverse osmosis membrane technologies, which have seen dramatic improvements in efficiency and cost in recent years, but remain an order of magnitude more energy intensive than conventional water treatment technologies. Desalination represents the ultimate trade off between climate change mitigation and adaptation - burning fossil fuels to avoid the impacts of increasingly frequent and intense droughts. Isolated desalination plants such as those in Sydney, Perth and London are powered by renewable energy, which is clearly preferable. However, in the wider context of moving to a low carbon economy, water utilities along with other sectors would be reducing overall energy use and switching to renewables, rather than using renewable energy to justify unprecedented energy demand from this new technology.

The thing that really worries me about desalination is that it essentially changes our relationship to water and the environment. Water, the great connector of life, becomes merely an industrial product, subject to the economic rules of substitution, with technology stepping in to meet endlessly growing demand at increasing cost of production. The people of the modern states of Western Australia and Israel, always tenuously perched in their desert surroundings, can now live without limits, fundamentally reorienting their sense of place and respect for their locality.

But the promise of no limits is always illusionary. As the adaptation-mitigation trade off shows, Prometheus is always punished. Water consumption inevitably leads to water pollution, as it flows through our homes, offices and factories, and back out again, contaminated, through our drains, to be treated once more, using high energy processes, before discharge to the environment.

Desalination is undoubtedly necessary in situations of acute shortage, as a stop gap measure in extreme events. Moving the entire basis of a water system to desalination, such as is taking place in Israel and Western Australia, is another matter. It is a responses to climate change that more firmly than ever entrenches the patterns of development that led to climate change. Living without limits is what got us into this mess. Breaching those limits is a very worrying place to go looking for solutions.



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