How Much Water Goes Out With the Trash Each Year?

Oranges rotting on a London market stall. Wasting food leads to the waste of huge quantities of water. Photograph: Martin Godwin via guardian.co.uk

As consumers throw millions of tonnes of uneaten food into the bin each year, few give a thought to the hidden cost of such waste – the water that it took to grow the food.

But new research shows that we throw away, on average, twice as much water per year in the form of uneaten food as we use for washing and drinking.

What is worse, increasing amounts of our food comes from countries where water is scarce, meaning the food we discard has a huge hidden impact on the depletion of valuable water resources across the world.

According to the first comprehensive study into the impact of the "embedded water" in the UK's food waste on world water supplies, more than a 5% of the water used by the United Kingdom is thrown away in the form of uneaten food. While these figures deal with the UK, I'm sure the numbers are indicative of most of the first-world countries; and, possibly some of the second-world countries as well.

The research was carried out by the government's Waste and Resources Action Programme (Wrap) and the green campaigning group WWF, and is published with the title: Water and Carbon Footprint of Household Food Waste in the UK.

The water used to produce food thrown away by households in the UK amounts to about 6.2bn cubic metres a year.

That represents 6% of the UK's total water footprint, which includes water used in industry and agriculture.

About a quarter of the water used to grow and process the wasted food originates in the UK, but much of it comes from countries that are already experiencing water stress.

Green campaigners have for years called for more attention to be paid to "hidden" or "embedded" water – water that is used in the production of all sorts of goods, from food and clothing to cars and furniture, and which represents a hidden cost on exports.

As more countries suffer from water scarcity, these exports can further deplete natural resources and cause environmental problems such as salination – which can render land unfit for growing crops – and higher prices for water to poorer consumers.

Food waste carries another environmental cost: it accounts for about 3% of the UK's annual greenhouse gas emissions, equivalent to the amount generated by 7m cars each year.

That is enough to cancel out the greenhouse gases saved each year by British households' recycling efforts.

Liz Goodwin, chief executive at Wrap, said: "These figures are quite staggering. Although greenhouse gas emissions have been widely discussed, the water used to produce food and drink has been overlooked until recently.

"However, growing concern over the availability of water in the UK and abroad, and security of the supply of food, means that it is vital we understand the connections between food waste, water and climate change."

She said the organisation – which is threatened with budget cuts – would work further with retailers, food and drink companies and local authorities to reduce the amount of food wasted.

David Tickner, head of freshwater programmes at WWF, said consumers could make a "small but very significant" contribution to reducing water stress if they tried to avoid wasting so much food.