Flawed Water Use Claims Are Huge Threat to Beef Sustainability

Let’s make a bet. I bet you that within the next five years, the biggest sustainability issue to hit the beef industry won’t be carbon emissions, hormone implant use or ethanol prices, it’ll be water use. Conflict over water rights and declining aquifer levels are already occurring in many areas and those battles will only increase as urban sprawl encroaches onto agricultural land.

Fortunately, scientists at the University of Twente in The Netherlands have calculated the water footprint* of humanity. Published in the highly prestigious Proceedings of the National Academy of Sciences, this study provides valuable evidence as to water consumption across different regions. Within the paper, beef production is singled out as contributing 6.7% to global water flows – less than cereals at 17% or industrial products as 12.2%.

Yet the message accompanying press coverage of the report is anything but positive for conventional beef production – a  ScienceNow press release (tagline: “Up to the minute news from science”) quotes Sandra Postel (director of the Global Water Policy Project) as saying:

…people can opt to eat less meat or to switch from grain-fed beef—which, again, requires about 5300 liters of water for each dollar’s worth of grain fed to a cow—to grass-fed beef, which typically requires only the rainwater falling on a pasture

Interestingly, the 5,300 liter (1,400 gallon) figure is not mentioned in the PNAS study, indeed there is no evidence as to the source for Ms. Postel’s claim. Furthermore, the figure is worthy of an award for what must be the most incomprehensible units ever assigned to water use. Expressing water use per acre or per unit of beef produced gives a solid foundation for understanding and comparison, but a volume unit per economic unit of feed fed to a beef animal? What happens when corn hits $10/bushel or falls to $3/bushel?

It’s a sad reflection upon my social life (or lack thereof) that I spent an hour last night calculating water use per dollar of corn fed. The entire calculation can be seen in the excel spreadsheet below, but in essence we simply need to know the current corn price ($6.335/bushel), the proportion of corn that is irrigated in the USA (15%), water use per acre of irrigated corn (2.1 acre-feet) and corn yield per acre (147.2 bushels).

Using these data, 110 gallons of water (417 liters) are used per $ of corn grain fed to a feedlot steer (equivalent to 44.9 gallons of water per lb boneless beef). That’s in line with the total water use of 367 gallons/lb boneless beef cited by Beckett and Oltjen at UC Davis.

Ms. Postel’s estimate is 12.7x higher than average USA data suggests. An error of this magnitude is huge and has the potential to do immense damage to the beef industry, especially when it’s used as a divisive argument against grain-fed production systems. Yet it’s published as factual data in a scientific press-release (without the need for citations or supporting evidence) and will be read by thousands of consumers with an interest in science. Just imagine the reaction from PETA and HSUS if the beef industry quoted environmental figures unsupported by science – instant loss of credibility.

As an industry, we need to be proactive and conduct assessments of resource use and environmental impact before the anti-animal groups or “impartial” environmental groups produce numbers for us. If we continue avoiding science for fear of what it might reveal, we may soon be reacting to a loss of consumer confidence and market share, rendering long-term sustainability impossible.

* Total water use by humans

Water use spreadsheet

6 thoughts on “Flawed Water Use Claims Are Huge Threat to Beef Sustainability

  1. I’m just so excited to find out that I can get rid of my water troughs for my grass-fed sheep- apparently rainwater is all they need!?! 😀


  2. Maybe Ms Postel was talking off the top of her head. It seems curious and rather unlikely she would intentionally obfuscate the facts given her credentials.

    I enjoyed your spreadsheet; very informative. 🙂


  3. Your math is really wrong here, and you’re the one disciminating bad information. Where you especially made a mistake is in calculating the water used per acre of corn. At 2.1 acre-feet of water and 43,560 square feet per acre that’s 91,476 cubic ft of water per acre of corn times 7.48 gallons per cubic foot equals 684,240 gallons per acre corn per growing season. Divided by 147 bushels per acre gives 4648 gallons per bushel divided by $6.33 per bushel that’s 734 gallons per dollar of corn about 6.7 x’s your figure. But that’s not right either because in the US most cattle are not entirely grain fed. In some markets beef cattle consume as much as 13kg of grain but the average is about 4kg of grain and 30kg of forage which has a different, much higher water consumption rate because of how much water is evaporated, most people don’t irigate those fields but that water consumption cannot be ignored even if it’s provided by rainfall or your numbers are useless. With those figures in mind Pimentel calculated that with grain supplemented diets cattle need about 105,000L per kg of beef produced all the way up to over 200,000L per kg produced on “free-range” or ranch land where there is less grain supplementing way back in 2003 and that has been the accepted standard in agriculture research for almost 10 years. Which of course was when corn was $3 per bushel but that doesn’t effect the water needed to grow food or the amount that the cattle consume. Can be read at http://www.ajcn.org/content/78/3/660S.long if you care to understand.


    • Brandon-
      Thanks for your comment. Unfortunately you’ve missed a crucial part of the equation – as mentioned in the blog post, the latest USDA irrigation survey, shows that only 15% of corn grain is irrigated. When that is taken into account (as you failed to do) your figures are reduced by a factor of 6.7 to give exactly the figure that I published in the blog – 110 gal/$ corn fed. Ms Postel’s comment related to grain-fed vs. grass-fed and suggested that grass-fed cattle only needed water inputs from rain compared to irrigation water + rain for grain-fed cattle. If we take that line of logic, it is entirely appropriate to simply examine irrigation water rather than total water use. The aim was not to determine total water use per unit of beef (a far more appropriate metric) but simply to examine Ms Postel’s claim.
      Pimentel’s work has certainly been accepted by many whose philosophical views agree with his findings, however, that does not mean that they are based on science or an understanding of animal production.


  4. Pingback: Is It Time We Stopped Shouting About The Dietary Guidelines? | Bovidiva

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