Water Consumption and Desalination

This article covers the topics of water consumption, desalination, and their connections to current environmental degradation and climate change.

Earth is the only planet currently known to harbour life, thanks to one particular resource, water. Throughout human history, civilizations that were able to harness freshwater for consumption and agriculture thrived. It’s why we see so many large cities around the world right beside a large body of freshwater. Today, 1 in 3 people do not have access to clean drinking water globally. However, according to Aqueduct World Resources Institute 2015, by 2040 most of the world won’t have enough freshwater to meet demand year-round. Why? In short, we have an increasing global population consuming more water on a planet with increasing droughts.

Figure 1 – water rich lifestyle vs water poor lifestyle facts and stats.

According to the World Bank 2013, the breakdown of the world’s freshwater consumption is about 8% for personal use, 70% for agriculture and 22% for industry. You might be surprised to hear that 22% of the world’s freshwater is used in industrial applications, but we don’t actually see all the water that is consumed in making the products we buy. Most of the water consumption comes from producing the ingredients used to make those products. For example, it takes 1650 litres of water to produce a ¼ pound hamburger. Almost all of that water is used for growing a crop called alfalfa, which is the most popular food for cows. Similarly, it takes 74 litres to produce a glass of beer, 130 litres to produce a cup of coffee, 142 litres to produce a slice of cheese and 2500 litres to produce a cotton t-shirt.

In 2018, Cape Town, South Africa became the first modern city that planned to shut off it’s water supply infrastructure. This was termed ‘Day Zero’ and would mark a day where over 4 million people would lose their supply of freshwater. According to the Climate Analysis Group at the University of Cape Town, 2017 was the driest year on record for the city. However, once the people of Cape Town heard about the looming Day Zero, they began to change their water consumption habits. Day Zero was pushed from March 18th 2018, to April 18th, then again to July 9th, and again to August, and again to 2019, and then the countdown to Day Zero was paused indefinitely. This was a testament to how much of an impact people can have if they are aware of how much water they are consuming.

Figure 2 – Agricultural water consumption stats.

One of the reasons so much water is used in the agriculture industry is because we often grow crops in places where rain is not a common occurrence. It really doesn’t make sense to grow alfalfa in the desert, but we do. India and China grow some of their most water intensive crops (sugarcane and wheat) in some of their driest locations. If crops were grown in more fertile areas, we could use that water to prevent Day Zero’s from occurring. A fraction of the water used to grow grapes for South Africa’s wine industry could be used to keep Cape Town’s water supply flowing. The scary thing is over the next decade, many large cities are going to come face to face with their own Day Zero. On the list are São Paulo, Beijing, Cairo, Moscow, Mexico City, London, Tokyo, and Miami.

Goldman Sachs predicts water will become the petroleum of the 21st century, and it’s being reported the availability of freshwater is increasingly driving violent conflict around the world. So what are we doing to stop this and prevent more Day Zero’s? One response has been to increase desalination infrastructure. Desalination is the process of removing the salt and other harmful particulates of saltwater to create freshwater. Given that 97% of the world’s water supply is in the form of saltwater, this seems like a logical approach. According to the World Health Organization International Water Summit 2017, the desalination of ocean water has more than doubled over the last decade. However, currently we only make 1% of the water we consume through desalination, which means we still have a long way to go.

Figure 3 – Desalination process.

The two main processes of desalination are distillation and reverse osmosis. In the distillation process, saltwater is heated up in a special container above its boiling point which then evaporates the water into water vapour and leaves the salt behind. The water vapour can then be cooled and collected as drinkable water. This process has been used by humans for centuries, but it is very energy intensive. A less energy intensive and newer process is called reverse osmosis. In essence, reverse osmosis works by pushing saltwater through a filter (called a semipermeable membrane) which will let water through, but not salt or other contaminants. Reverse osmosis was a breakthrough technology and has been the reason arid countries like Saudi Arabia have been able to sustain growing populations.

Figure 4 – Reverse osmosis process.

According to the International Desalination Association, in 2011 over 65% of desalination plants in the world used the reverse osmosis process, and that number has definitely grown in the last decade. Unfortunately, reverse osmosis is not a perfect technology. While it is less energy intensive than distillation, it does still require a significant amount of energy to run. This energy is usually acquired by burning fossil fuels which contribute to climate change, which is a main reason why we are facing the water crisis in the first place. Another con is when you take 2 litres of salt water and run it through a reverse osmosis process, you get 1 litre of freshwater and 1 litre of water that is very concentrated with salt which is called saline water. Since we don’t have a good use for saline water right now, it is usually dumped back into the ocean where it has a harmful effect on marine life. So while we are making progress with desalination technology, we still need a lot more advancements before we can rid the world of impending Day Zero’s.

Today we value water so little, the amount we pay for it doesn’t even cover the cost of transporting that water to us. On July 28th, 2010, the UN recognized access to freshwater as a basic human right. But how are you supposed to value an invaluable resource so that everyone has it? Putting more money into researching new desalination techniques will hopefully get us there eventually, but for now it looks like the only immediate response is to follow in the footsteps of Cape Town and consume responsibly.

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