Virtual water and water footprint: why 1 kg of beef takes 15,400 litres

Virtual water is the water used to make a product: it does not show in the product, but it was spent in the field, on the farm, in the factory and on the way to the shelf. The water footprint adds up that water along the whole chain, and the numbers are striking: as a global average, a kilo of beef takes 15,400 litres and a cup of coffee 130, according to studies from the University of Twente, in the Netherlands. For a company, the water footprint starts at the meter of its own operation and runs all the way to its suppliers.

In short:

• The concept of virtual water was created in 1993 by British professor Tony Allan, who received the Stockholm Water Prize for it in 2008.
• The water footprint splits water into three colours: blue (from rivers and aquifers), green (rain stored in the soil) and grey (the water needed to dilute pollution).
• Global averages: beef 15,400 litres per kilo, pork 6,000, chicken 4,300, wheat 1,827; coffee 130 litres per cup and tea 27.
• For beef, 93% of the footprint is green water, the rain that falls on pasture and feed crops; blue water is less than 4%.
• In a company, the part it controls directly is the blue water of its own operation, and water footprint management starts by measuring, reducing and reusing that water.

What is virtual water?

It is the water a product carries without containing it. A kilo of wheat weighs a kilo, but to produce it the crop used, on global average, more than 1,800 litres of water. When a country imports wheat, it also imports that water, which stayed in the producing country.

The idea was put forward in 1993 by Tony Allan, a professor at King’s College London, to explain how water-poor countries in the Middle East managed to feed themselves: by importing food, they imported the water they did not have. The concept changed the debate on trade and water policy, and earned Allan the 2008 Stockholm Water Prize.

For Brazil, a major exporter of grain, meat and coffee, virtual water has two sides. It is an advantage, because much of that production runs on rain, and a responsibility, because the blue water withdrawn for irrigation and processing competes with every other use in each river basin.

What is the difference between virtual water and water footprint?

Virtual water is the concept; the water footprint is the measure. Proposed by Professor Arjen Hoekstra, of the University of Twente, the water footprint adds up all the water used directly and indirectly to produce a good, a service or the consumption of a person, a company or a country, and says where it came from:

Colour	Where it comes from	Example
Blue	Rivers, lakes and aquifers, withdrawn and consumed	Irrigation, industrial process water, water built into the product
Green	Rain that stays in the soil and is used by plants	Rain that feeds pasture and rain-fed crops
Grey	The volume needed to dilute pollution to an acceptable level	Fertiliser nitrogen that reaches the river

The split changes everything. In global crop production from 1996 to 2005, the footprint was 78% green, 12% blue and 10% grey. Blue water is the one that competes with city supply and industry, and grey water measures the weight of pollution.

Do not confuse the two: grey water in the water footprint is not the “greywater” of reuse, which is water already used in sinks and showers that can be treated for toilet flushing and washing. The names are the same; the ideas are not.

How much water lies behind what we consume?

The values below are global averages calculated by Mesfin Mekonnen and Arjen Hoekstra, of the University of Twente, and include all three colours:

Product	Global average water footprint
Beef	15,400 litres per kilo
Olive oil	14,500 litres per kilo
Sheep meat	10,400 litres per kilo
Pork	6,000 litres per kilo
Goat meat	5,500 litres per kilo
Chicken	4,300 litres per kilo
Eggs	3,265 litres per kilo
Wheat	1,827 litres per kilo
Maize	1,222 litres per kilo
Milk	1,020 litres per kilo
Apples	820 litres per kilo
Oranges	560 litres per kilo
Coffee	130 litres per cup, with 7 grams of roasted coffee
Tea	27 litres per cup, with 3 grams of black tea

Why does meat weigh so much? Because the animal needs to eat a lot to gain a kilo, and every kilo of feed carries the water of the crop. According to the same study, the water footprint per calorie of beef is 20 times that of cereals and roots, and almost a third of the world’s agricultural water footprint is linked to animal products.

Two cautions before comparing. The global average hides big differences between countries and production systems, and the study itself warns that the comparison changes from region to region. And colour matters: of the 15,400 litres for beef, about 93% is green water, the rain that falls on pasture and feed crops, and less than 4% is blue water. The impact on rivers depends far more on the blue and grey parts than on the total.

Why does the water footprint matter to a company?

Because the water a company uses does not end at the meter. Three reasons are pushing the subject up the agenda:

• Supply chain risk. A raw material supplier in a water-scarce basin is a risk of shortage and of price. The water footprint shows where the dependence lies.
• Reporting. GRI 303, the water standard for sustainability reports, asks for the operation’s withdrawal, discharge and consumption volumes, and investors and customers increasingly ask about the supply chain. What goes into the report is in ESG and water management.
• Standard. ISO 14046, published in 2014, sets out principles and requirements for assessing the water footprint of products, processes and organisations based on life cycle assessment.

For most service, retail and healthcare companies, the direct footprint is small next to the supply chain footprint. Even so, it is the only one the company controls on its own, and the one that shows up on the bill every month.

How do you calculate a company’s water footprint?

In five steps, from what the company measures to what it estimates:

1. Blue water of the operation. Add up the consumption from each source, utility, well and own abstraction, per site, with reliable metering. Everything else rests on this.
2. Grey water of the operation. From the volume and quality of the effluent, estimate how much it weighs on the receiving river.
3. Supply chain. For the most relevant inputs, use averages from the literature, like those in the table above, or data from the suppliers themselves.
4. Hot spots. Cross the volumes with the water stress of each basin: a litre used where water is scarce weighs more.
5. Targets. Decide where to cut first, with a deadline and an owner, starting with what is under direct control.

The first step usually reveals the first saving: metering exposes leaks, out-of-hours consumption and equipment that uses too much. The full roadmap is in the guide to water savings in companies.

How do you reduce the operation’s water footprint?

With the same fronts as water management: find and eliminate losses, replace equipment that uses too much, reuse where quality allows and measure all the time. Every litre of blue water the operation stops withdrawing cuts the direct footprint and the bill.

• Leaks: continuous loss that enters the footprint without producing anything. See invisible leaks: how to find them.
• Reuse: the same water used twice. The step by step is in water reuse in industry.
• Continuous metering: without it, the footprint is an estimate. With remote monitoring, it becomes a monthly number.

T&D helps the company with that part. HydroDesk combines technology bought by the company, team training and remote consulting, in a four-phase journey that reaches GRI report preparation and SDG mapping. SEA 360º handles implementation and ongoing management, with monthly efficiency and ESG impact reports.

Frequently asked questions

How many litres of water does a kilo of beef take?

On global average, 15,400 litres per kilo of beef, according to Mekonnen and Hoekstra (University of Twente). About 93% of that volume is green water, the rain used by pasture and feed crops. Chicken comes to 4,300 litres per kilo, and pork to 6,000.

What is grey water in the water footprint?

It is the volume of water needed to dilute the pollution from an activity to an acceptable level in the receiving river, such as fertiliser nitrogen. It is not the greywater of reuse, which is water already used in sinks and showers that can be treated for other uses.

What is the difference between a water footprint and a carbon footprint?

The carbon footprint adds up the greenhouse gases emitted by a product or activity. The water footprint adds up the water used and polluted, and says where it comes from: rivers and aquifers, rain or the dilution of pollution. One does not replace the other.

Is there a standard for measuring the water footprint?

Yes. ISO 14046, published in 2014, sets out principles, requirements and guidelines for assessing the water footprint of products, processes and organisations, based on life cycle assessment.

How can you reduce your water footprint day to day?

By wasting less food, which carries the water of the whole chain, and by saving the water that passes through the meter, at home or at work. The measures, with the litres each habit uses, are in 15 ways to save water.

Sources

• Mekonnen, M. M.; Hoekstra, A. Y. The green, blue and grey water footprint of crops and derived crop products. Value of Water Research Report Series No. 47, UNESCO-IHE, 2010: water footprint of crops, coffee, tea, fruit and olive oil, and the green, blue and grey split of global crop production
• Mekonnen, M. M.; Hoekstra, A. Y. A Global Assessment of the Water Footprint of Farm Animal Products. Ecosystems, vol. 15, 2012: water footprint of meat, milk and eggs
• Stockholm International Water Institute: “Virtual water innovator receives Stockholm Water Prize”, 2008
• ISO 14046:2014, Environmental management: Water footprint, catalogue entry at SIS, the Swedish standards institute
• T&D HydroDesk and SEA 360º