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http://everylastdrop.co.uk/ says "When you consider the water required to produce all the stuff we consume, we actually guzzle a massive 4,645 litres every day". It then lists several specific cases, including:

  • 1 kg cotton = 20,000 litres, and
  • 1 cup of coffee. 130 litres

Are these two claims true?

DarkLightA
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    I can't cite my own experience, so I'll just comment: I grow and process my own coffee. There's no *inherent* need for anything like that much water: water is used in the demucilaging bath, but that's low volume. So presumably they mean irrigation, but that varies by location (I use none, but nearby commercial farms have drip systems). Even if one does include irrigation, what's the definition of "taking" water? It's not removed from the water cycle. Many farms, at least here in Kona, Hawaii, are organic and don't use/minimize pesticides and runoff. – Larry OBrien Sep 07 '13 at 21:34
  • Partial duplicate: http://skeptics.stackexchange.com/questions/512/does-it-take-200l-of-water-to-make-a-latte?rq=1 –  Sep 07 '13 at 22:31
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    define "use water" first – ratchet freak Sep 07 '13 at 22:42
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    @ratchetfreak The asker doesn't need to define the term. The source says that these figures represent "the water required to produce all the stuff we consume". If there's ambiguity in that, then so be it. A good answer will address that issue. –  Sep 07 '13 at 22:45
  • @LarryOBrien It's easy to find other web sites e.g. http://watertcd.blogspot.fr/2010/10/one-cup-of-coffee-is-equivalent-to-130.html which make the same claim using the same numbers. Also the the web site referenced in the OP is "in partnership with [Waterwise](http://www.waterwise.org.uk/)" which may have [references or resources](http://www.waterwise.org.uk/resources.php) on their web site. – ChrisW Sep 07 '13 at 23:45
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    Just for reference, here are the steps in producing coffee at the totally personal level: http://www.knowing.net/index.php/2009/06/09/coffee/ – Larry OBrien Sep 08 '13 at 03:55
  • These numbers definitely include irrigation (including rain), and sound about right - I'll try to find a serious reference and post an answer but the claims are true. – Ofir Sep 08 '13 at 09:12
  • @Sancho without specifying what's included and excluded in the claim, there's no verifying the claim and someone can always state "but, you didn't..." or "but, I didn't mean that...". If 2000 liters is needed, but 99% of that is reclaimed some way (or can be counted towards other things), I'd say actually only 20 liters are needed but the claimant may not agree. – jwenting Sep 09 '13 at 11:11
  • @jwenting Since the claim only gives clarification that the number means the "water required to produce all the stuff we consume", it's up to the answerer to state their assumptions in interpreting that. If you have an interpretation that results in 20L are needed, go ahead and write it up as an answer. A *great* answer, though, would follow the claim through its sources and find out in what sense the claim means what it says. In either case, it's definitely not up to the asker to impose a definition upon a claim that may or may not match what was actually meant. –  Sep 09 '13 at 14:58
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    @Sancho not so. If that 2000L needs to be applied, it can be considered to have been used even if the net use after recovery and beancounting side benefits is far less. And that's the point. Without knowing what the actual claim is, there's no debunking it. – jwenting Sep 09 '13 at 15:07
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    @jwenting If the 20000L is only correct when not considering recovery etc, then say that *in an answer*. And also say why that sense of "use" is not meaningful. You've also ignored this: "*A great answer, though, would follow the claim through its sources and find out in what sense the claim means what it says.*" –  Sep 09 '13 at 15:09
  • @jwenting Why would you expect the asker to have some omniscient point of view that gives them access to what the claim means? –  Sep 09 '13 at 15:13
  • @Sancho his claim, he sets the parameters. I'm not going to second guess him when he shoots down anything I write because "it's not what I had in mind". – jwenting Sep 09 '13 at 19:34
  • @jwenting. It's not his claim. The claim is that of the linked website. He is only asking about that website's claim. –  Sep 09 '13 at 21:01
  • At my Ecology class at university they taught us that similar ot the cited amounts of water are used for producing paper, bread, everything. That is, water is very significant input for the industry. Conclusion: those numbers are likely correct, and citations are to be searched in **engineering ecology** texts. – Vorac Sep 16 '13 at 08:39

1 Answers1

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I get about:
coffee: 80 liters per cup
cotton: 10000 liters per kg
The differences could be due to the original calculation including run off pollutants. But the numbers are actually pretty close for a back of the envelope calculation. There are some details about this in the cotton water footprint report below.

Cotton:
http://www.cottoninc.com/fiber/AgriculturalDisciplines/Engineering/Irrigation-Management/Cotton-Water-Requirements/
looking at the averages of cotton requirements for the three time periods in the table I get:
(25 * .09) + (35 * .22) + (50 * .30) = 24.95 inches of water per acre
1 acre = 6272640 sq inches
6272640 sq inches * 24.95 inches = 156502368 cubic inches per acre
156502368 cubic inches = 2564610 liters per acre

https://www.cotton.org/econ/cropinfo/costsreturns/usa.cfm
Taking the average of "Cotton Yield: pounds per planted acre": 495.56, 667, 591
584.52 lbs per acre = 265.134 kg per acre
265.134 kg per acre / 2564610 liters per acre = 9672 liters per kg

This is a pretty interesting paper on the water footprint of cotton:
http://www.waterfootprint.org/Reports/Chapagain_et_al_2006_cotton.pdf
for virtual water average in the world total cost (pg. 192)
cotton lint: 8506 cubic meters per ton = 9376.2 liters per kg
end textile: 9359 cubic meters per ton = 10316.5 liters per kg
this seems to confirm my above calculations

Coffee:
http://www.waterfootprint.org/?page=files/CoffeeTea
claims 140 liters per cup

http://www.britannica.com/EBchecked/topic/124337/coffee-production
seems to agree with:
http://www.ancoracoffee.com/class/Fast_Facts_About_Coffee.aspx
~2000 lbs of beans per acre
http://www.coffeeresearch.org/coffee/roasting.htm
~17% weight loss (can apparently be higher or lower depending on the darkness of the blend) http://store.starbucks.com/Coffee-Preparation-FAQ/coffee-prep-faq,default,pg.html
A 1-lb bag of coffee yields approximately 64 5-oz cups* (320 oz) (53 6oz cups)
This is pretty close to most of what the individuals say that I could find ~50 cups so I'll use this number.
http://www.soap.com/p/folgers-100-columbian-ground-coffee-27-8-oz-211123
1 lb 11.8 oz (1.7375 lbs) = 240 6oz cups
But here is an up to amount from a folgers label: 240/1.7375 = 138 cups per lb

http://www.britannica.com/EBchecked/topic/124337/coffee-production
60 to 80 inches (I'll average the two and use 70)

70 inches * 1 acre = 7 195 310.72 liters per acre
2000 lbs of beans per acre
2000 lbs * .83 (less 17%) = 1660 lbs of roasted beans per acre
1660 * 53 = 87980 cups of coffee per acre
82 liters of water per cup of coffee

Adam Phelps
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  • It important to say that this usage of water isn't "destroying" the water. It is cycled back to nature. – T. Sar May 26 '17 at 10:48
  • No usage of water really "destroys" the water from an environmental standpoint other than cracking it open to get the hydrogen for use in nuclear fusion. – Ben Barden May 26 '17 at 13:44
  • @BenBarden - That's different than what TSar is saying. If I remove water from the groundwater sources, use them for irrigation, for cranberry bogs, or other uses, then they are taken out of the normal water cycle. Aquifers, streams and water bodies lower or dry up completely. Trees and plants using normal rainwater is going to happen whether or not we plant, coffee trees, harvest the beans and drink the coffee is more the point. However, most coffee berries are "wet processed" to remove fruit pulp and get the "bean," so I'm not sure how much that plays into the original claim. – PoloHoleSet May 26 '17 at 15:01
  • @PoloHoleSet I'm reading the direct claim made by TSar, and things like irrigation and cranberry bogs absolutely have the water "cycled back to nature". – Ben Barden May 26 '17 at 15:51
  • @BenBarden - not sure how dried up streams and lakes qualify as "cycled back to nature." By your standards, *nothing,* ever would not qualify, as you stated, which is obviously not what TSar is talking about. You're being excessively pedantic and literal. Try going with obvious intent, or ask for clarification if that intent isn't clear. That kind of strict literalism, if applied universally, would make communication impractically tedious. – PoloHoleSet May 26 '17 at 16:27
  • @PoloHoleSet - part of my point was that his statement was at best deeply vague, and possibly either trivial or false. It contains little to no useful information, and inviting us to put our own meaning on it via "obvious intent" doesn't help that. So far as I can see, part of the *point* of skeptics is to keep language clear so that this sort of fuzziness doesn't interfere with understanding. – Ben Barden May 26 '17 at 19:56
  • @Ben Barden: But the original question and its variations ARE inherently fuzzy. As for instance, if you grow your cranberries in a naturally boggy place, you'll use the same amount of water as if the bog was left wild and filled with cattails & sedges. OTOH if you try growing cranberries in the Mojave Desert, you'll need much more water than would support the native vegetation. – jamesqf May 27 '17 at 05:20
  • @Tsar I agree. The original claim has some connotations that I hope my post clears up. – Adam Phelps May 27 '17 at 13:53
  • @BenBarden A lot of the claims you hear about water seem to suggest it's a finite resource that we are using up and then we'll have no water. It is true that there are many examples of freshwater resources that we have spoiled. But I think they are generally unrelated to water usage, such as runoff. Only a small amount of that water is taken out of the cycle by photosynthesis. And most of that will be returned again. – Adam Phelps May 27 '17 at 14:09
  • I think, more than that, isn't whether water eventually gets returned to the water cycle, but whether it is available for the natural water table and ecosystem. So plants that normally use rainwater, just as other plants would if not for human intervention, will have relatively minimal impact vs water that is diverted from the aquifers. So, IMO, not just runoff having an impact and not just spoilage of water sources. – PoloHoleSet May 30 '17 at 13:25