Can we drink our oceans? Five things you need to know about desalination

Desalination is key to providing fresh water to millions of people around the world. Yet, it can harm marine wildlife, takes a lot of energy, and it's often not sustainable.

Providing fresh water for the 10 billion people expected to live on Earth by 2050 is one of the biggest challenges of our century.  

Nature and Environment | 26.06.2018

When the first desalination plants began operating in the mid-1960s, they were hailed as a great solution to make our oceans drinkable. But the alchemy of extracting salt is not without negative environmental impacts. 
Find out what it takes to produce fresh water, and you may never look at your tap in the same way.

Why is desalination important?

Although water covers about 70 percent of Earth's surface, only 2.5 percent of it is fresh. And 70 percent of that tiny fraction is trapped in glaciers and ice caps, which leaves less than 1 percent to meet our drinking, hygiene, agriculture, and industrial needs. 

While rivers, lakes and underground sources still provide most of that fresh water, our changing climate is leading to greater depletion of this most primary resource. More than one in four people already face water scarcity, and the World Health Organization says the number could reach one in two by 2025.

Nature and Environment | 28.03.2018

Water consumption varies widely. In rich countries, one person uses up to 80 liters of water at home every day just for such things as taking a shower, cooking and flushing the toilet; in very poor countries, people might have fewer than 10 liters per day to meet all their needs.

How does desalination work?

There are two main ways in which salty water is made fit for human consumption: thermal desalination and reverse osmosis. 

Thermal desalination causes the water to evaporate and condense, leaving salt and other impurities behind, while reverse osmosis uses a filter membrane that only allows water molecules through, thereby separating it from salt and other substances. 

Because reverse osmosis, which was invented in the US in the 1950s, is the more energy efficient of the two approaches, it is more widely used. Around 70 percent of desalinated water is achieved using this process.

Once the water is purified, minerals and chemicals are added to meet the standards required for safe and healthy drinking water. 

Infografik Wie Osmose funktioniert EN

If we can drink our oceans, will that solve the water shortage problem?

It's not quite that simple. Although desalination provides a solution in particularly dry regions, such as the Middle East and North Africa, it is a highly energy-intensive process. And one that's often powered with fossil fuels.

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The upshot is emissions which contribute to global warming. An estimated 76 million tons of CO2 are emitted annually as a result of desalination processes.

So, while there is more water to satisfy global thirst, the process of generating it is feeding into the very warming that is contributing to depleting natural sources. Desalination plants powered by renewable resources are attracting increasing attention.

How much water is currently drawn from our oceans?

Worldwide, there are some 16,000 desalination plants in more than 100 countries. Collectively, they can produce 95 million cubic meters of fresh water per day, which is enough to supply around 300 million people.   

Seventy percent of facilities are located in wealthy countries, the majority of them in the Arabian Peninsula, where about half of the world's desalinated water is produced. 

In this arid region, freshwater resources are scarce, but access to seawater is easy — and oil and gas are cheap. Desalination plants there are powered by waste heat from fossil fuel power stations.

Infografik Karte Desalination capacity by region EN

What happens to the salt that's removed from the sea?

Most of it is dumped back into the water, together with chemicals used during the desalination process. 

About 142 million cubic meters of brine, the salty slush generated through the creation of drinking water, are returned to the sea every day. That would be enough to cover the entire surface of Germany.

Saudi Arabia, the United Arab Emirates, Kuwait and Qatar are responsible for 55 percent of global brine production. 

Due to its dense concentration, brine sinks and spreads along the seafloor, where it can interfere with entire marine ecosystems. It is particularly harmful in semi-closed seas such as the Persian Gulf. 

Global desert: Drought turning the planet into a tinderbox

Australia: 'Land of drought'

Australian Prime Minister Malcolm Turnbull, addressing the drought in the state of New South Wales, which produces one-quarter of the country's agricultural output, said, "Now we are the land of drought." Australia recently passed legislation to provide hundreds of millions of dollars worth of relief aid to farmers, including funds for mental health support.

Global desert: Drought turning the planet into a tinderbox

Ethiopia: The end of nomadic life?

Ethiopia has been suffering from ongoing drought conditions since 2015, causing massive food shortages. The Ethiopian government said that some 8.5 million citizens required emergency food assistance in 2017 and that nearly 400,000 infants suffered acute malnutrition. Furthermore, the drought threatens to end traditional nomadic herding in the region.

Global desert: Drought turning the planet into a tinderbox

South Africa: The looming prospect of Day Zero

Conservation and late-season rains saved South Africa's Cape Town from an apocalyptic Day Zero scenario, in which water would have to be turned off and emergency rations issued, The drought, which was one of the worst in decades, emptied water reservoirs and caused some experts to suggest hauling icebergs from Antarctica avert a crisis.

Global desert: Drought turning the planet into a tinderbox

Europe: Withering crops

Europe's sweltering heat has been compounded by a lack of rain. Not only have citizens been suffering the health consequences, which affect health care systems and labor productivity, crops have also been hit hard. Farmers across the continent fear bankruptcy due to poor crops and the EU Joint Research Center predicts "an increase in drought frequency and intensity in the future."

Global desert: Drought turning the planet into a tinderbox

Greece: Lost villages reappear as crops die

Greece has been facing the dual problem of flash flooding in some regions and drought in others. Crete's farmers said they could lose up to 40 percent of their crop this year due to an extremely dry winter. Though they are watering, they say it is not enough to nourish their crops. Water levels are so low that previously submerged villages have begun to reappear in reservoirs across the country.

Global desert: Drought turning the planet into a tinderbox

Sweden: Worst drought since 1944

Sweden, which has not seen rain for over three months, is experiencing its worst drought since 1944. The situation threatens to cause severe crop losses costing farmers hundreds of thousands of euros. Sweden has been the site of massive forest fires and has even seen temperatures exceeding 30 degrees Celsius (86 degrees Fahrenheit) in the Arctic Circle.

Global desert: Drought turning the planet into a tinderbox

UK: 'Tinderbox conditions'

The United Kingdom fears serious threats to its food supply chain due to the effects of this summer's drought. The country's National Farmers Union said the country is experiencing "tinderbox conditions." This adds to problems brought on by the prospect of needed self-reliance in the event of a no-deal Brexit.

Global desert: Drought turning the planet into a tinderbox

India: Running out of water

India has been plagued by water shortages due to rising population and mismanagement but also aggravated by drought, causing many areas of the country to run out of water. Bangalore was recently added to the list of global cities most likely to run out of drinking water. Other cities on the list include Cape Town, South Africa; Jakarta, Indonesia and Sao Paolo, Brazil.

Global desert: Drought turning the planet into a tinderbox

USA: Back to the Dust Bowl

The US government said 29 percent of the country is currently experiencing drought, with conditions affecting some 75 million people. Although wildfires in California have captured the world's attention, farming states, like Kansas, have once again been suffering. Kansas was one of the states crippled by the famous 1930s Dust Bowl.

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