Desalination and Climate Change
By Jan Tao
Climate change has wreaked havoc in many parts of the world. Extreme weather, loss of habitats, and extinction are just snippets of the devastating effects. The worst is yet to come. In some countries, the increased number of droughts has led to a constant shortage of water. To combat this, they have turned to desalination, removing salt from seawater to create fresh water for drinking and agricultural use. Desalination might sound like a perfect solution to tackle both the issues of freshwater shortage and rising sea levels, but it almost seems too good to be true. Is there a catch to it?
What is it?
Desalination is not an innovative technology; one of its equivalents, distillation, is one of the earliest water treatment processes that is still used to this day by some bottled water brands. Saline water is sprayed on heated pipes so that pure water evaporates into steam. This steam is used to heat the heated pipes in subsequent stages to distillate more water to be as energy efficient as possible. The production of rain is an example of the natural distillation of seawater powered by solar energy. Another desalination method is reverse osmosis: the net movement of water from an area of low water potential to an area of high-water potential through a partially permeable membrane. Or, in simpler terms, the procedure of pushing water through an exceptionally fine filter, where everything except for water molecules is too large to get through and is filtered out. Although both methods sound simple, the cost to do this at a large scale is monumental; thus, this may not be the go-to solution for certain nations struggling with water scarcity.
The reason why desalination is so expensive is the energy needed to keep these plants running. Billions of watts are required to separate pure water from solutes and impurities, and on top of that comes another cost to pay- the environmental baggage. 89% of the energy consumed in 2018 in the UK came from non-renewable energy sources, such as fossil fuels and natural gas, and as we all know, they contribute to climate change. This means that if humans were to rely on desalination for freshwater, there would most definitely be a considerable increase in energy consumption, which will intensify the effects of climate change, such as more droughts. Thus, it begins a never-ending vicious cycle. Clearly, desalination at a large scale should be discouraged.
Besides, a highly concentrated salt solution is produced as a by-product of desalination, which is dumped back to the sea. This change of salinity can harm the organisms living nearby, provided that they were not sucked in and killed by the pump of the facility already.
With humankind’s demand for freshwater increasing every day, there are efforts to improve the sustainability of desalination, such as integrating silica gels, rechargeable batteries and solar panels, which increase energy efficiency, or in the latter case, eliminating the need for non-renewable energy.
But instead of spending millions to produce freshwater as efficiently and cheap as possible in the future, shouldn’t we focus our efforts on the present? Practicing rainwater capture is an example. Also, being an ancient technology, coastal cities can store their rainwater in tanks inside buildings for non-potable uses, such as gardening and flushing toilets. It can also be purified for drinking. Currently, places such as Melbourne, Bermuda and Manchester harvest their water, and in Singapore, up to 30% of its water comes from rainwater capture.
‘Water, water everywhere, nor any drop to drink’, freshwater shortage is a pressing concern that has to be dealt with. Otherwise, this scene from Samuel Taylor Coleridge’s ‘The Rime of the Ancient Mariner’ will be a reality for many of us in the not-too-distant future.