Comments on: Flawed Water Use Claims Are Huge Threat to Beef Sustainability

By: bovidiva

bovidiva — Fri, 24 Feb 2012 19:07:38 +0000

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.
Jude

By: bovidiva

bovidiva — Fri, 24 Feb 2012 19:00:16 +0000

Michelle – Like magic isn’t it?

By: Brandon May

Brandon May — Fri, 24 Feb 2012 17:14:05 +0000

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.

By: friznecker

friznecker — Fri, 24 Feb 2012 09:51:21 +0000

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.

By: Michelle Canfield

Michelle Canfield — Fri, 24 Feb 2012 06:09:26 +0000

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!?!