A Sustainable Steak?: The Mathematics of Nutrient Cycles

I spent the morning reading Adam Merberg’s fascinating blog, http://saywhatmichaelpollan.wordpress.com/ Merberg often comments here at eatingplants.org and I’d encourage a careful look at whathe’s up to. In any case, this post comes directly from what I learned from Merberg’s work. Thank you, Adam.

“A truly sustainable agriculture,” Michael Pollan writes on his blog, “will involve animals.” The justification for this claim, one that’s been further popularized by Lierre Kieth’s The Vegetarian Myth and Simon Fairlie’s Meat: A Benign Extravagance, is that animals “complete the nutrient cycle.” Because ruminant animals return to the earth the nutrients they take from it, and because the process is driven exclusively by solar power, Pollan and others are able to justify meat eating on environmental grounds. “Eating a steak at the end of a short, primordial food chain comprising nothing more than ruminants and grass and sunlight,” Pollan writes, “is something I’m happy to do and defend.” The vast majority of the sustainable food movement would certainly agree.

But Pollan, as well as the sustainable food movement, may very well be defending the indefensible. The most conspicuous example of a supposedly high-functioning nutrient-cycling, diversified farm is Joel Salatin’s Polyface, Inc.–made famous by Pollan’s Omnivore’s Dilemma.  Salatin’s meat, according to Pollan, looks “an awful lot like the proverbial unattainable free lunch.”  However, according to Adam Merberg, a PhD student in mathematics at Berkeley and author of a blog that mathematically scrutinizes Pollan’s major claims, lunch from Polyface is significantly more costly than it seems. The story of the nutrient cycle, it turns out, is a bit more complex than Pollan claims it to be.

Pollan’s steak actually has a lot to do with chickens. Merberg notes that Polyface produces over 12,000 broiler chickens year.  These birds, as Pollan describes their role, do more than meet local demand for chicken flesh.  They’re essential to enhancing soil fertility. Without chicken poop, fertilizer would have to be imported into the system. The catch here is that Polyface (according to Merberg’s estimation) imports roughly 144,000 pounds of feed a year–mainly in the form of corn, soy, and oats–in order to nurture their clucking fertilizer machines (which produce lush pastures to keep the cows well fed).

What this means is that the nutrients that chickens return to the soil are outsourced, leaving a plot of land somewhere outside the Polyface cycle devoid of its nutrients. Pollan writes that, “The chief reason Polyface Farms is completely self-sufficient in nitrogen is that a chicken, defecating copiously, pays a visit to virtually every square foot of [the pasture] at several points during the season.” But that nitrogen, of course, came from elsewhere.

This hidden cost effective torpedoes the idea not only of a closed system, but a free lunch as well. Given that such “self sufficiency” is directly due to externalized environmental degradation (growing corn and soy), Merberg calculates that Polyface ultimately consumes more calories than it produces.  The farm (again Merberg stresses that these are estimates) imports 244,800,000 calories a year and it produces 171, 368, 236–leaving it with a net loss of over 73,000,000 calories of food energy. To convince himself these these numbers were not radically off the mark, Merberg actually asked Salatin at a recent Berkeley conference this simple question: “Do you get more out of the farm than you put into it?” Merberg, cited the environmental cost of grain and, on this basis, surmised the answer was “no.”  To his surprise, Salatin responded, as Merberg puts it, “that I was exactly right.” Salatin added (in Merberg’s paraphrase) “that other people say his farm is sustainable, but he doesn’t advertise it as such.”

In fairness to Polyface, it does remarkably better than industrial methods of animal production. But, to be sure, it’s offering no free lunch, nor is it “truly sustainable.” The nutrient cycle spins not only on sun, but on energy purloined from grain–energy that the animals are not able to return to the cycle.  Merberg’s assessment of his own findings is admirably conservative. He never concludes that we should all run off and eat grain–in fact he treads lightly around the entire vegetarian/vegan debate, evidently awaiting more detailed information before making comparisons.  There’s no denying, though, that animals raised in rotational grazing systems fail to “complete the nutrient cycle.”

“Every time we take food–whether it be from plant or animal source–from a farm,” Merberg writes, “we’re taking nutrients away.” From a narrowly defined idea of environmentalism, it seems safe to say that we need to minimize the impact of what we exact. I find it hard to believe, based in part on my assessment of Merberg’s work, that a pound of flesh could ever cost less (environmentally) than a bushel of grain.











About James McWilliams
I'm a historian and writer based in Austin, Texas. This blog is dedicated to exploring the ethics of eating animals and animal-based products.

9 Responses to A Sustainable Steak?: The Mathematics of Nutrient Cycles

  1. CQ says:

    Thanks, Adam. Thanks, James.

    What do you make of these claims, Adam: http://features.csmonitor.com/environment/2009/01/20/could-cows-heal-the-west

    Does Polyface not have the acreage to do rotational grazing?

    What are these folks missing about true sustainability?

    Why aren’t more farmers trying/promoting this: http://stockfreeorganic.octoberbooks.org

    • Keith Akers says:

      I found the Christian Science Monitor article here:

      The “rotational grazing” referred to in the article is Allan Savory’s “holistic resource management” or “holistic management” (HRM or HM, depending). If you use the word “holistic” enough, you can convince environmentalists (including, now, Frances Moore Lappe) that what you’re doing is just fine. It’s basically a flaky idea that never quite becomes big enough to generate significant attention and refutation.

      George Wuerthner discusses Savory here (PDF):

      Jeff Burgess discusses Savory here:

      Frances Moore Lappe backs Allan Savory’s claims in her book “EcoMind,” which I discuss in a rather lengthy discussion of her chapter 3 here (scroll about 3/4 of the way down to get to the part about Allan Savory):

    • Adam Merberg says:

      As is characteristic of these kinds of stories, the information isn’t specific enough to understand what is happening on these farms. I’d want to know, at very least, whether the farm has any inputs, particularly water, which is scarce in dry western states, and fertilizers. As for holistic management more generally, Keith seems to know much more about it than I do. There is also some mention in Simon Fairlie’s book, and he seems somewhat skeptical, particularly of the carbon sequestration claims.

  2. CQ says:

    Good links, Keith.

    I read Wuerther’s public lands ranching piece and thought this paragraph proved his (and your) argument well: “Areas protected from livestock grazing offer the most telling evidence that munching cattle are not a prerequisite to ecosystem health. Forest Service researchers recently published a study of Dutchwoman Butte in Arizona. This isolated mesa top had never been grazed by livestock yet was “striking in the diversity, density, and vigor of the grasses” and remarkably free of plants such as curly mesquite and snakeweed, which are undesirable forage plants and quite common on sites grazed by livestock. The amount of forage on the butte was four times that found in similar livestock-grazed areas despite the occurrence of a severe drought at the time of the study.16 There are other livestock-free places throughout the West—though rare due to the ubiquity of livestock—that further make the case that plant communities thrive in the absence of grazing domestic animals.17”

    And at the end of his article, he includes a quote by Lynn Jacobs in “Waste of the West” (1991) that I very much agree with: “HRM [holistic resource management, now shortened to holistic management] promotes the dangerous philosophy that humans are capable of, and should be, managing a planet. It does not recognize the integrity of the natural environment, its right to free existence, or humans’ place in it.”

    Your rebuttal of FML makes sense to me. While I can see why it’s in cattlemen’s interests to defend HM, I don’t see why she of all people is so dazzled by Savory/HM.

  3. Adam Merberg says:

    Thanks for this post.

    Although my numbers on Polyface are estimates, I think they’re all fairly conservative in the sense that I tried to make them as sympathetic to Polyface as I could. For instance, I couldn’t find the feed conversion ratio for the farm’s eggs, so I just ignored the feed for layer hens. If I had used a typical number, the figure for the input calories would have been approximately double what I came up with. And similarly, if I had included pig fodder, that would have been another quite substantial increase.

    I feel comfortable saying that Polyface isn’t an environmental solution, but I don’t think that the calculation has broader applicability. If you accept the results of my calculations and conclude that Michael Pollan has it wrong on Polyface, it doesn’t make much sense to trust that Pollan has correctly determined the “best” meat farm. I would rather get that information from somebody who has an agricultural background.

  4. rhys says:

    “The justification for this claim, one that’s been further popularized by Lierre Kieth’s The Vegetarian Myth and Simon Fairlie’s Meat: A Benign Extravagance, is that animals ‘complete the nutrient cycle.'” Have you read Meat: A Benign Extravagance? Merberg would obviously have a better sense of this than I do, but based on Fairlie’s book and what I’ve read by Merberg, I don’t think Fairlie and Merberg would disagree much on the science of nutrient cycles. Though I’d love to see a “Say What, Simon Fairlie?” blog if they did.

    • Adam Merberg says:

      Yeah, I’ve still only read a little bit of Fairlie’s book, but I don’t think he takes this position. In fact, he makes the point that Pollan’s claims about Polyface’s productivity are impossible and that Polyface is “only half a farm.” My impression is that Fairlie’s book has much stronger intellectual foundations than Pollan’s, so it would probably take somebody with an actual agricultural background to critique it in an interesting way. Pollan ran afoul of high school chemistry and biology, which is something I can handle.

  5. Would also like to see the water usage of Polyface farm. I understand that a pound of flesh requires 2500-5000 gallons of water. Or is this calculated within the calories? What does Pollan and Polyface have say about this as far as sustainability? http://www.earthsave.org/environment/water.htm

    Thank you for another excellent article!

  6. Provoked says:

    Along with water I’m wondering too if these calculations also include the redundant use of pesticides, herbicides, etc. and the killing of wild-life as further consequences to harvesting grain to feed chickens to nourish the soil to feed the cattle?

    That’s probably a horribly constructed sentence – My thinking cap has grown ever tighter absorbing all this information about the ins and outs of what goes in and comes out of the earth! I’m grateful for the added knowledge and when I’m challenged again about nutrient management, closed systems and other sustainable issues I’ll know where to point for the right answers. Thank you.

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