(Guest Post by Alex Cull)
Amongst all the alarming factoids relating to water that appear in Prof. Steve Emmott’s play “Ten Billion” (and possibly also in his forthcoming book), few can have been more alarming than the one about chocolate, i.e., that it takes 27,000 litres of water to produce one bar of the stuff.
Quite a few reviewers of the play refer to it. Journalist Matt Trueman writes: “Essentially, Emmott frames the whole system in economic terms, to show that as a species we are living on massive credit. A single bar of chocolate, for example, requires 27,000 litres of water for its production. By the time a car has been made, it has already had a significant enough impact on the environment that driving it is negligible. These resources cost the planet, but it’s future generations that will pick up the bill. Our current mode of existence is unsustainable. And, short of behavioural or political changes so radical that they’re unthinkable, it will continue to be so until the end, because we are a species in denial, failing to investigate the possible slim, slim hopes for averting the impending crisis.” 
The tone of the play, and of the reviews, is one of shock and horrified disbelief – 27,000 litres of our precious, life-giving water is being squandered every time a chocolate bar is produced. Wicked waste! No wonder we’re doomed.
As with beef (see my previous post) two basic questions we can ask are:
1) Is this 27,000 litres/choc bar figure accurate?
2) Does it matter, anyway?
So, firstly, where does the figure of 27,000 litres come from? Strangely, I’ve found this number difficult to track to its source. It’s found on quite a few websites, notably Urban Times  but these don’t tell us how the figure is derived. However, Urban Times links to a website that you will be familiar with, from my post about beef – waterfootprint.org. 
Locate chocolate in the Product Gallery on waterfootprint.org, and you will immediately see that the figure there is actually 17,196 litres per kilogram. Chocolate is made from cocoa paste, which is reckoned to have a water footprint of 24,000 litres/kilogram, but is also made from cane sugar at 1800 litres/kilogram, so the finished product comes out at a global average of about 17,000 litres/kilogram.
It’s very different to what Prof. Emmott appears to have been saying. This is what I think might have happened.
1) Water engineers Mekonnen and Hoekstra produced their report “The green, blue and grey water footprint of crops and derived crop products” in 2011 , which gives a figure of 17,196 litres of water to produce one kilogram of chocolate, and which is available on the waterfootprint.org website.
2) Landscape architect Claire Thirlwall wrote an article for Urban Times about water use in the chocolate industry, also in 2011. It’s actually a balanced and sensible article, but what may have occurred (my apologies to Claire if this is not the case) is she saw “17,000” as “27,000”, which is why she wrote “… that bar of chocolate needs a staggering 27,000 litres of water per kilo.”
3) Professor of Computational Science Steve Emmott was gathering material in late 2011 or early 2012 for his upcoming play “Ten Billion” and read the Urban Times article. What may have occurred (my apologies to Steve if this is not the case) is he saw “that bar of chocolate needs a staggering 27,000 litres of water”, without noticing the “per kilo” at the end.
And that is possibly how “Ten Billion” ended up with the remarkable and also horribly inflated number of 27,000 litres per chocolate bar.
The other basic question is: does it matter, anyway? As with grass-fed beef, the answer is: no, not really. The water that goes to produce chocolate is, according to waterfootprint.org, 98% green, 1% blue and 1% grey. The reason for that is not hard to work out – much of it comes from places like Ghana, which enjoy vast amounts of rainfall each year. If cocoa beans were not cultivated there, the water would simply go to nourish other plants in the rain forest and continue on its path around the hydrological cycle. Ghana – as Claire Thirlwall notes in her Urban Times article – scores a very relaxed 0% on the Water Stress Index. 
The fact that a tiny part of Ghana’s bounty of rainwater (a natural, free, renewable resource) is diverted into making chocolate bars, is neither here nor there in the grand scheme of things. It doesn’t exactly “cost the planet”, and it doesn’t hurt the Ghanaians, whose economy is set to grow something like 5.5% this year, which will raise living standards and also, hopefully, improve working conditions there. Nothing is actually going to waste.
Which makes it all the more ironical to find a report into food waste (“The water and carbon footprint of household food and drink waste in the UK“, published in 2011 jointly by WRAP and WWF) which specifically mentions chocolate as one of the “top two products in the list of water footprint of household food waste” (the other worst offender, you will not be surprised to learn, is beef.) 
“Chocolate is another example of contrasting impacts. The quantity of chocolate thrown away is relatively small (24,000 tonnes of chocolate bars plus 7,000 tonnes in hot chocolate). Its contribution to the carbon footprint of food and drink waste is also small (117,000 tonnes CO2 equivalent), yet it significantly contributes to the water footprint of food waste, accounting for over 750 million cubic metres of water.”
If it weren’t so laughable, it would be quite infuriating to receive stern lectures from WWF about your “water footprint of food waste” based on such ridiculously shaky foundations. Enough to make you boiling mad, perhaps, or “like water for chocolate”, as the Spanish expression goes.
In a lighter vein, I’ll leave you with something that could be called the choco-hydrological cycle (or maybe the hydro-chocological cycle, I can’t decide which.) You might like to hum the Circle of Life theme from Disney’s “The Lion King”, while reading this – just a thought.
1) Rain falls from the skies in equatorial Africa, nourishing all the plants in the tropical rain forest ecosystem.
2) Some of that rainfall goes to nourish cocoa trees, cultivated by enterprising people in Ghana.
3) The cocoa is turned into chocolate – Mekonnen and Hoekstra reckon it takes, on average, about 17,000 litres of water to make a kilogram.
4) An internet article inflates that 17,000 litres to 27,000 litres of water per kilogram of chocolate.
5) Prof. Emmott then multiplies this by a factor of 10 to arrive at an incredible 27,000 litres of water per chocolate bar.
6) At the performances of “Ten Billion”, audiences are shocked and horrified by this huge figure.
7) Reviewers mention it in their reviews – more people read them and are shocked and horrified.
8) Overcome by shock and horror at the information, people rush out to buy and consume great quantities of comfort food, especially chocolate.
9) The chocolate is digested, nature takes its course and all residual water contained in the chocolate is ultimately returned to the biosphere.
10) The cycle begins all over again.