FACTBOX: How much "virtual water" do you use every day?

by Emma Batha | @emmabatha | Thomson Reuters Foundation
Tuesday, 24 July 2012 10:00 GMT
Why a pint of beer is more than just a pint of beer

** This factbox is part of AlertNet's special multimedia report on water. Visit "The Battle for Water" for more**

LONDON (AlertNet) - If you had a cup of coffee, a couple of slices of toast and an egg this morning, you also inadvertently consumed around 450 litres (120 gallons) of water - enough for three typical baths.

That’s a calculation made according to a global water footprint standard that seeks to measure both direct and indirect uses of water in everything from making cars to growing apples.

The indicators underline that water is not just for washing and drinking. The world uses phenomenal amounts of water to produce food, clothes and other basics taken for granted every day.

The water embedded in products is sometimes referred to as "virtual water". So how much of this hidden water do you use in a day? The following will give an idea.

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If you want to work out your own water footprint, the Water Footprint website has a calculator. And click here to watch anAlertNet animation about virtual water and food.

    * Cup of coffee (125 ml) – 130 litres

    * Mug of tea (250 ml) – 30 litres

    * Glass of milk (250 ml) – 255 litres

    * Pint of beer (568 ml) – 170 litres

    * Small glass of wine (125 ml) – 110 litres

    * Steak (250 grams) – 3,850 litres

    * Block of cheese (250 grams) – 1,265 litres

    * Egg (60 grams) – 200 litres

    * Bread (one slice) – 60 litres

    * Rice (1 kg) – 2,500 litres

    * Potatoes (1 kg) – 290 litres

    * French fries (1 kg) – 1,040 litres

    * Tomato - 50 litres

    * Tomato ketchup (1kg) – 530 litres

    * Apple – 125 litres

    * Large banana - 160 litres

    * Chocolate bar (100 g) – 1,700 litres

    * Pizza Margherita (725 g) – 1,260 litres

    * Jeans – 8,000 litres

    * Cotton shirt – 2,500 litres

    * Car – 50,000 litres

    * Biofuel (1 litre) - 3,500 litres

(Sources: Water Footprint Network, Virtual Water and Comprehensive Assessment of Water Management in Agriculture. Estimates for many of the above can vary. 1kg = 2.2lb, 1 litre = 1.76 UK pints / 2.1 US liquid pints)

In detail: Cotton, meat, bread, coffee and sugar

Cotton

Cotton is the world’s largest non-food crop. The impact its cultivation can have on water sources is seen dramatically in Central Asia's Aral Sea. Once one of the world’s largest lakes, the Aral has lost around 80 percent of its volume due to water being diverted from the rivers that feed it to boost cotton production in the arid region. (See these NASA pictures published by France 24).  

Globally, the average water footprint of cotton fabric is 10,000 litres/kg so a cotton shirt might use about 2,500 litres and a pair of jeans about 8,000 litres. But the footprint varies from place to place - for fabric made with cotton from China it’s 6,000 litres/kg, from Uzbekistan 9,200 litres/kg and India 22,500 litres/kg.

It’s important to look not only at the size of the footprint but at what proportion of water comes from sources like rivers and lakes (known as blue water) as opposed to rain (known as green water). Blue water use is high in Turkmenistan, Uzbekistan, Egypt, and Pakistan.

Cotton production not only depletes fresh water sources but also pollutes them due to high levels of insecticide and fertiliser leaching into the groundwater.

This UNESCO report on cotton points out that about 84 percent of the water footprint of cotton consumption in the European Union is located outside Europe, with major impacts particularly in India and Uzbekistan.

It says cotton consumers have little incentive to take responsibility for the impact on water systems in other countries due to a lack of proper water-pricing mechanisms.

Other estimates for jeans are lower. Levis, which uses cotton from the United States, says one pair of its jeans would use around 3,500 litres in a lifetime including washing. The company is trying to reduce water and pesticide consumption in the cotton industry.

Meat

Rising consumption of meat is likely to increase pressure on global water resources. The average footprint of the most popular meats stacks up like this: beef cattle 15,400 litres/kg, sheep 10,400 litres/kg, pig 5,990 litres/kg, goat 5,520 litres/kg and chicken 4,330 litres/kg. 

But the footprint of one piece of beef or lamb may be very different from another as it depends on the production system - grazing, mixed or industrial - as well as the composition and origin of the feed. 

The global water footprint of beef production is about a third of the water footprint of all animal production in the world.

Industrially produced beef generally uses less water than beef from mixed or grazing systems. But it uses more water from surface and ground sources, as opposed to rain water, and causes more water pollution. That means grazing systems are better for conserving water resources.  

Animal products generally need more water than crop products. Beef has an average footprint per calorie 20 times larger than cereals. The footprint per gram of protein is six times larger than for pulses. Click here for a table comparing food types.

Bread (from wheat)

The global average water footprint of wheat is 1,827 litres/kg. A kilo of flour makes about 1.15 kg bread, giving a footprint of 1,608 litres/kg.

But this varies a lot depending on the origin of the wheat and how it was grown. In western Europe, the water footprint of wheat is far below the average. A French baguette (baked with French wheat) has a water footprint of 155 litres. A German roll has a footprint of about 40 litres and Dutch bread works out at about 18 litres a slice.

Coffee

Coffee is the world’s most valuable traded agricultural product in dollar terms. But producing it requires a lot of water – each drop of coffee needs more than 1,000 drops of water. Most of it is for growing the coffee plant.

The world requires about 110 billion cubic metres of water every year to keep drinking coffee. This is the same as 1.5 times the annual run-off of Europe’s Rhine river.

Sugar

Sugar is largely produced from sugar cane and sugar beet. Sugar from cane needs far more water than from beet. The footprint of refined beet sugar is about 920 litres/kg compared to 1,780 litres/kg for refined cane sugar. Sugar cane is often irrigated.

Globally, surface and groundwater account for just over a quarter of the crop’s water footprint, but in places like Pakistan’s Sindh province it can be 80 percent. 

Sugar cane and sugar beat are also used to produce biofuels. The footprint for bio-ethanol from sugar is lower than for bio-ethanol from maize or bio-diesel from soybean.

And if you’re going to buy pizza buy it in France!

The cheese topping accounts for about half the 1,260-litres used to produce an average pizza margherita (725 g). But the footprint varies widely between countries.

In Italy, the home of pizza, a margherita would work out at 940 litres/kg, in China 1,370 litres/kg, in the United States 1,200 litres/kg. But in France it’s just 540 litres/kg.

Source: Water Footprint Network

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