[This is a guest post by Alex Cull]
In his play “Ten Billion”, Stephen Emmott makes several references to the amount of water required for food production, stating that:
1) 3000 litres of water are needed to make one beefburger.
2) 30 trillion litres are used annually in the UK burger industry.
3) 27,000 litres are needed to make one bar of chocolate.
4) 100 litres are needed to make one cup of coffee.
Firstly, it might be a good idea to explain the three different classes of water that are often mentioned when someone tries to calculate a country’s or an industry’s “water footprint”. These are “green water” (rainfall), “blue water” (water abstracted from rivers or pumped from aquifers) and “grey water” (any extra water required to assimilate pollutants.) Many publications refer back to studies by water engineers Mesfin M. Mekonnen and Arjen Y. Hoekstra in the Netherlands, which are also used on the waterfootprint.org website maintained by the University of Twente .
Clearly, using “green water” is the most desirable path to raising beef, from an environmental point of view, and “blue water” the least. And this is what waterfootprint.org says about beef:
“The production of one kilogram of beef requires 15 thousand litres of water (93% green, 4% blue, 3% grey water footprint). There is a huge variation around this global average. The precise footprint of a piece of beef depends on factors such as the type of production system and the composition and origin of the feed of the cow.”
This must be where the figure of 3000 litres per burger comes from, although the weight works out at about 200g per burger, which seems suspiciously generous; a “quarter-pounder”, after all, would be only about 113g. Thus we can immediately see that beef production uses water that is 93% “green”. That is the global average, however. It is the UK that Emmott specifically mentions, stating in “Ten Billion” that here in Britain we get through 10 billion burgers in a single year (and thus 30 trillion litres of water, if the 3000 litres per burger figure is accurate.) And it does appear that the figures might be exaggerated. The UK has a population of around 63 million. It would mean that each of us, on average, would need to eat almost 160 beefburgers a year, roughly one burger every two and a quarter days. Is that correct? It seems a colossal number of burgers per person, per year. In addition, the rate of 1kg of beef per 15 thousand litres of water is a global average (and thus very approximate – there is a “huge variation”, remember), and the 200g weight per beefburger seems mysteriously ample. Taking all these factors into account, Emmott’s numbers could be way too high.
However, as will be revealed, even if they were to be entirely accurate, these calculations would also be almost completely irrelevant, to a UK audience at least. Britain’s beefburgers come from a variety of sources, but it might be worthwhile to glance at one of the biggest vendors of burgers, which is restaurant chain McDonald’s. Where do McDonald’s in the UK get their beef from? According to their website: “McDonald’s UK only uses 100% British and Irish beef to make our burger patties”. 
Let’s look at England, then, as an indicator. According to a document called “Testing the Water” produced in 2009 by EBLEX (English Beef & Lamb Executive) the proportions of green/blue/grey water, with regard to English beef production, are: green 84%, blue 0.4% and grey 15.2%. The EBLEX publication also has some interesting things to say about the impact of green and grey water.
“Green water… is the rainfall used by crops (including grass) at the place where it falls. This water is essentially unavailable for other uses. In the absence of grassland or crops, it would be consumed to almost exactly the same extent by other vegetation. Indeed, deeper-rooted tree and scrub cover would lead to even higher levels of water use than crops or grassland. And the alternative of leaving the land bare is neither feasible without considerable input to restrict natural regeneration, nor desirable in terms of soil erosion and run-off. Since it cannot be used elsewhere and levels of usage are not increased by its role in crop production, green water consumption carries little or no hydrological impact. Grey water is a notional provision, representing the volume required to dilute pollutants to levels that maintain defined water quality standards. It also carries relatively little hydrological impact since it does not physically consume the resource and deny it for other uses. After all, water notionally required to reduce the biological oxygen demand of accidental slurry or silage effluent leaks, or counter higher than acceptable nitrate or phosphate concentrations from soil leaching, is, at the same time, also available to meet human consumption or environmental maintenance needs. Grey water as a concept is, arguably, of most value to water companies as a measure of the ‘cost’ of countering any negative water quality impacts from farming.”
Green water use is not a problem, then, economically or environmentally, and grey water use is not a problem either. Which leaves blue water (abstracted from rivers or pumped from aquifers) – and only 0.4% of English beef production uses blue water. The situation is similar in Ireland (and probably Wales and Scotland too) although the rates for imported beef might, of course, be different. So the fact, therefore, that 30 trillion (or fewer) litres of water might be used annually in the UK burger industry represents something of a complete and utter non-problem, especially when the beef in question is raised domestically. All but a tiny part of the water that nourishes the cattle that provide the beef to make the burgers falls from the sky as rain and if it was not used would drain away into the ground and be lost. At least where water use is concerned, eating a McDonald’s beefburger in the UK ought to be a guilt-free experience.