Food production given wake-up call over water scarcity

A blue paper was launched during the recent World Water Week​ event in Stockholm, which was attended by over 50 international organisations. While accepting that more water for food production will be necessary in the short term, the scientists behind the study stressed that how much water, where it comes from and the environmental and social consequences of its use will depend very much on decisions made in the next few years.

"The bottom line is that groundwater levels are plummeting and our rivers are already overstressed, yet there is a lot of complacency about the future,"​ said Dr David Molden, principal scientist with the International Water Management Institute​ (IWMI).

The food-processing industry has always been a major water user. Water is used as an ingredient, an initial and intermediate cleaning source, an efficient transportation conveyor of raw materials, and the principal agent used in sanitising plant machinery and areas.

The UK's Environment Agency estimates that the British food industry alone consumes approximately 900 megalitres of water each day, enough to supply almost three-quarters of all customers' needs in London daily. Huge volumes of water are transformed into vapour during the food production process, while a significant percentage is discharged as wastewater.

Although water use will always be a part of the food-processing industry, it has become the principal target for pollution prevention and source reduction practices.

For example, the Stockholm blue paper echoes the findings of a report released at the 12th meeting of the UN Commission on Sustainable Development (CSD 12) earlier this year. The survey, entitled Water - more nutrition per drop,​ highlighted the need to identify and influence unsustainable food production patterns that require excessive water usage.

Significantly, one of the key findings of the report was that it is consumers - not producers - who are now driving global food production. With massive urbanisation and increasing wealth, food preferences are changing, with significant increases in the demand for meat and dairy products.

Population increase and the demand for more affluent diets containing more animal protein will have a significant impact on food production. According to the International Food Policy research Institute​, diet changes significantly as incomes rise. At first, more food is consumed; then animal protein replaces vegetable protein.

The UN survey points out that it takes 7,000 litres of water to produce 100 grammes of beef, as opposed to 550 litres to produce enough flour for a loaf of bread. Powerful consumer trends, such as the widespread adoption of low-carb diets, are changing people's eating habits, and producers are rushing to satisfy these changing dietary demands within a highly competitive market.

But both government and the industry accept that something must be done. With prevailing food production practices, a balanced diet requires 3,287 litres of water per day compared to the 50 used for an average household's domestic needs, according to the Stockholm International Water Institute (SIWI).

One method of achieving greater water efficiency is of course to reuse it. Spent process water in the food industry can be desalinated and organics can be removed so as to fulfil the requirements for reuse.

EU food industry standards specify that spent process water intended for reuse (even for cleaning purposes) must be at least of drinking quality. Regulations for other applications, such as boiler make-up water or warm cleaning water, are even more stringent.

Lenntech​, a water purification and air treatment firm, highlights a recent study on the possibilities for reuse of vapour condensate in a milk processing company (dried milk production) as boiler make-up water, and the reuse of chiller shower water in a meat processing company (sausage production) as warm cleaning water.

The study shows that on the basis of the treatment of two low contaminated process water streams in the food industry applying a combination of pre-treatment, membrane filtration and UV disinfection, treated water of a defined quality can be obtained.

The report also shows by numerous chemical and microbiological analyses that with a two-stage membrane combination of nanofiltration, process water can be obtained with a quality good enough for boiler make-up water or warm cleaning water.

Similarly, the United Nations Environment Programme​ (UNEP) points out that water, which is used extensively in meat processing, can be recycled to achieve cleaner production. The organisation says that businesses should analyse water use patterns by installing water meters, and regularly record water consumption.

Some data should also be collected outside normal working hours to identify leaks and other areas of unnecessary waste. Once water use for essential operations has been optimised, water reuse can be considered.

For example, wastewaters that are only slightly contaminatedcould be used in other areas. Defrost water fromrefrigeration systems and vacuum pump water is usually clean, andcould be reused for non-critical applications. Water used for carcasswashing could be recirculated. Wastewaters from the slaughter floor,washbasins, knife and implement sterilisers and carcass washing couldbe reused for gut cutting and washing.