Elements

When food passes its expiration date, do you toss it into the bin? I do. Last week, I threw out half a bag of bread, three quarters of a box of tomatoes, and a packet of sliced chicken breast that was four days past its use-by date. That’s a lot of food gone to waste. In fact, according to a report by the U.N. Food and Agriculture Organisation, 1.3 billion tons of food in the world are lost each year. If the majority of water we consume comes from food, how much water are we wasting when we throw out our food?

To answer that, Professor Tony Allan from King’s College London came up with the concept of “virtual water” to determine the amount of water that goes into the production of food.

What is virtual water?

UK’s virtual water website defines the concept as “water used in all the processes involved in producing goods and food”. For example, a tonne of wheat can require three million litres of water to produce; and if you think that’s a lot, a tonne of beef can require up to 16 times as much. That amount includes not only drinking water for the cows, but water that goes into growing the food that feeds them as well.

According to Prof Allan, the concept of virtual water helps countries measure the amount of water needed in production of goods. This especially allows water-scarce countries to better manage their limited water resource. The concept also ensures food security through the trading of “water intensive commodities” from water rich countries — such as Brazil and Canada — to water poor countries like Israel and Singapore.

In the UK, 40% of the food consumed is imported. In Singapore – a country that doesn’t have a natural water supply – the majority of its food, like fruit and vegetables, is imported from countries such as Malaysia that has enough land and water to grow them.

Big water versus small water

Until recently, the UK had experienced some of its driest weather, which led parts of the country being declared in a state of drought. Posters reminding the public to conserve water could be seen in London underground stations up until a few months ago.

However, the water that we’re told to save – by taking shorter showers, reducing the frequency of car washes, and washing dishes in a tub of water – is what Prof Allan refers to as “small water”. This is because such daily usage of water is only a small proportion when compared to what is used in the production of commodities, which Prof Allan calls “big water”.

So agriculture actually takes up a larger share of the water we use, and with the global population currently estimated to be at 7 billion, it’s possible the demand for food will soon outstrip the amount of water needed to produce food.

Possible solutions

All hope is not lost though. Prof Allan suggests that the solution lies in finding ways to increase the production of food from every 1000 litres of water.

“If we can use clean energy to produce desalinated water for less than a dollar [per 1000 litres]…a proportion of the [problem] could be solved”.

By encouraging farmers to use water effectively, it’s possible to generate more food to keep up with the increasing population. He also says that manufacturing desalinated water cheaply is another way of addressing the water issue.

However, Professor David Seekell from the University of Virginia disagrees: “The source of long-term water shortages is our large population and the growing number of people with high standards of living. I think engineered solutions are unlikely to overcome this fundamental issue.”

His recent research,published in the IOP Publishing’s journal Environmental Research Letters, has found that virtual water might not be the best answer to resolve global water inequality.

“Inequality in this sense refers to when a small population uses a disproportionately large amount of a resource,” Prof Seekell explains. “For instance, if 10% of the global population is using 90% of the freshwater we would refer to this as inequality.”

Prof Seekell and his team wanted to find out if the virtual water concept is able to redress this inbalance. Some countries may use more water than others, and the effectiveness of virtual water is limited by geographical factors such as climate and arable land.

It seems that there is no definite remedy to the global water problem. But until one is discovered, perhaps understanding virtual water is our best bet in ensuring water security for the future.

Image: author’s own

Seekell, D., D’Odorico, P., & Pace, M. (2011). Virtual water transfers unlikely to redress inequality in global water use Environmental Research Letters, 6 (2) DOI: 10.1088/1748-9326/6/2/024017