Fossil fuels, chemical fertilizers, and farm animals

Michael Pollan moves on from his brief discussion of wild animal deaths on farms to point out certain environmental challenges of a vegan world. He argues,

The vegan Utopia would also condemn people in many parts of the country to importing all their food from distant places. In New England, for example, the hilliness of the land and rockiness of the soil has dictated an agriculture based on grass and animals since the time of the Puritans. (326)

New England has left the time of the Puritans, however. Tofu and soymilk from Vermont-grown soybeans can now be found in some New England grocery stores. Production of wheat in New England has also increased recently. Maine-based farmer Eliot Coleman has written numerous books on growing organic fruits and vegetables in places like New England. (The page of Coleman’s latest book, The Winter Harvest Handbook, includes a glowing endorsement from Michael Pollan, so perhaps this claim will be updated in the next edition of The Omnivore’s Dilemma).

Pollan continues,

To give up eating animals is to give up on these places as human habitat, unless of course we are willing to make complete our dependence on a highly industrialized national food chain. That food chain would be in turn even more dependent than it already is on fossil fuels and chemical fertilizer, since food would need to travel even farther and fertility — in the form of manures — would be in short supply. (326)

This is a very bold claim. Pollan isn’t merely saying that the most sustainable agriculture would include some farms like Polyface Farm. He’s suggesting that we’d use more fossil fuels and chemical fertilizers with a vegan food system than we do now by feeding grain to cattle. (Update: Commenter Eric B argues that this isn’t what Pollan is saying.)

Even if we accept the premise that food would need to travel significantly farther in a vegan world, Pollan is wrong to say we’d need more fossil fuels. Any increase in fossil fuels use for transportation would easily be offset by reduced production energy. In their book Food, Energy, and Society, David Pimentel and Marcia H. Pimentel (whom Pollan cites for much of his data on energy use in the food supply) estimate that producing food for a vegan diet requires about 18,000 kilocalories of fossil fuel energy per day, compared to 35,000 kilocalories for a nonvegetarian diet (Figure 11.1, page 134). They also estimate (page 258) that transporting 1 kilogram of food 1,000 kilometers from the farm to cities and towns uses 640 kilocalories of fossil fuel energy. If we combine this with David and Marcia Pimentel’s estimate that Americans consume about 1000 kilograms of food per year (computed for a lactoovovegetarian and nonvegetarian diet, but I doubt that vegan should require much more food mass), it turns out that we’d have to move our vegan food more than 9,600 kilometers to offset the production energy savings the vegan diet offers over the nonvegetarian diet. In other words, even if we ignored the energy used to transport food today, and even if our hypothetical vegan country shipped all of its food 5,600 kilometers from San Diego, California to Calais, Maine, the vegan nation would still be considerably less dependent on fossil fuel energy.

As for chemical fertilizers, I’m not going to do a calculation because numbers are a bit harder to come by here, but I think Pollan has that wrong, too. If we ate our grain instead of feeding it to livestock, we’d need far less of it, and most grain today is grown with chemical fertilizer (as Pollan has told us earlier).

Pollan adds that the vegan world wouldn’t have farm animals to provide manure and tells us, “it is doubtful you can build a genuinely sustainable agriculture without animals to cycle nutrients”  (326), two claims related to issues I’ve addressed before. Pollan hasn’t addressed the fact that the nutrients in manure come from the food that animals eat. Last time I wrote,

[W]hen animal manure is used to fertilize plants, the nitrogen it provides was fixed either [chemically] by the Haber-Bosch process or by nitrogen-fixing bacteria in the roots of plants. Any nitrogen animals leave on the pasture was ingested in their food. This is a point that Pollan seems to miss when he writes,

The chief reason Polyface Farm is completely self-sufficient in nitrogen is that a chicken, defecating copiously, pays a visit to virtually every square foot of it at several points during the season. (210)

Polyface Farm isn’t completely self-sufficient in nitrogen, though. There’s plenty of nitrogen in the eighty percent of the chickens’ diet that Pollan has told us (just a few sentences earlier) comes from  corn and soy that Salatin buys. For the soil to maintain a stable nitrogen level from year to year, it’s necessary for the chicken feed together with the nitrogen-fixing bacteria in the roots of clover  and other legumes to provide enough nitrogen to replenish whatever is removed from the farm in food for humans. Passing through the chickens’ digestive systems doesn’t increase the amount of biologically-available nitrogen in the feed.

The farm where the chicken feed is grown is depleted of nitrogen when the corn and soy are removed to feed Salatin’s chickens. Thus, as I wrote last month, it makes little sense to say that animals “cycle nutrients” on the farm. The word “cycle” suggests that the animals are somehow returning nutrients to the farm. That’s not what animals do. They take nutrients from plants (like grasses) that aren’t directly usable to humans and bring them into our food supply by fertilizing plants we can eat with their manure. Putting animals on the farm doesn’t change the need to replenish the nutrients that are removed in the form of food for humans. Sometimes these nutrients can be replenished naturally, by growing leguminous plants (like clover), but even at Polyface Farm, it’s necessary to import fertility from a neighboring farm in the form of conventionally-grown corn.



  1. […] Peter Singer, The Omnivore's Dilemma After completing his factually dubious (see here and here) takedown of the “vegan Utopia” in The Omnivore’s Dilemma, Michael Pollan is […]

  2. […] New England to import all of their food from distant places. It’s a dubious claim in view of existing production of soy, wheat, and vegetables in New England. He even goes so far as to suggest that the vegan food chain would be more dependent […]

  3. Eric B. said

    I think you overstate your case a little in this post. The nitrogen that Salatin imports, for instance, is coming mostly from soybeans which fix nitrogen with little or no help from synthetic nitrogen fertilizer (albeit with plenty of other chemical fertilizers and other chemicals), so that farm could theoretically sell soybeans indefinitely without ever returning any nitrogen to that soil in the form of manures or fertilizer. Even Salatin’s purchased corn crop, while heavily dependent on synthetic nitrogen fertilizer, isn’t really impacting long-term nitrogen levels on those farms, because plant-available forms of nitrogen don’t stick around long. My state’s soil testing service makes nitrogen (unlike P & K) fertilizer recommendations with no regard to soil tests, because they figure nitrogen doesn’t persist in the soil long enough even from year to year to make a difference. There are, nonetheless, lots of very unsustainable things about the way Salatin buys in grain and how those farms operate, including depletion of other soil nutrients and including the depeletion of fossil fuels for the sake of synthetic nitrogen fertilizer and including all the dangers of pesticide-intensive agriculture.

    I also think farm animals do play a very important role in “cycling nutrients” insofar as they collect them (as by grazing) and concentrate them in the form of manure such that those nutrients can efficiently be put in places where farmers need them (e.g. in gardens). My nutrient cycles certainly wouldn’t be as complete without animal manure. It is misleading to speak of cycling, though, when the cycle doesn’t come full circle as when sewage treatment plants send nutrients down rivers or to landfills. Some treated sewage does get applied to fields, but there are obviously huge problems with regards to humanure and completing nutrient cycles. As for Salatin, if the manure he collected from his animals (e.g. from the barn in the winter) were returned to the field growing the grain, it would make even more sense to talk about animals cycling nutrients.

    On another point, I think there’s a little more truth to Pollan’s statement about the vegan dependency on fossil fuels and chemicals than you allow. Insofar as Pollan’s suggesting that, as you say, “we’d use more fossil fuels and chemical fertilizers with a vegan food system than we do now by feeding grain to cattle,” I wouldn’t dispute the point, but that’s not exactly what he said. Pollan talked about dependency. A vegan food system would be dependent on fossil fuels and chemicals in a way that traditional food systems weren’t (and reincarnations of which wouldn’t have to be.) Obviously, our current food system is terribly dependent on those things, but insofar as independence is our goal, veganism stands to hinder our goals. In that sense veganism makes us more dependent on the system, even if it does so in lesser amounts.

    This is true in another sense besides what Pollan said about manure, and that’s that vegan alternatives to animal products (particularly the protein substitutes like soy and dry beans, and the non-animal fats) are some of the most expensive foods to grow (esp. relative to their industrial counterparts) without fossil fuel powered combines. The scale dictated by combine-harvesting generally necessitates the accompanying problems of increased fossil fuel dependency with regards to transportation. That scale also is responsible for the disconnect between consumers and the land that feeds (and clothes, etc.) them, and that disconnect has been the great facilitator for the chemical abuses and all the other abuses (including our very poor stewardship of animals) of our industrial system of agriculture. One might even argue that veganism leads to abuses of farm animals, insofar as those abuses are a part of our industrial food system and veganism increases our dependency on that system.

    • Adam Merberg said

      Thanks for this comment, and I’m sorry it’s taken so long for me to reply. You raise some good points, some things I disagree with, and some things I’ll want to think about more.

      Your point about nitrogen is one of the aforementioned good points, though its usefulness is perhaps limited. Nitrogen was not a great choice of example on my part, but the point that outside inputs are still needed on the some farm is essentially correct.

      Regarding nutrient cycling, the point I was trying to make was this one: “It is misleading to speak of cycling, though, when the cycle doesn’t come full circle as when sewage treatment plants send nutrients down rivers or to landfills.” Generally, I don’t have a problem with using misleading terminology, so long as it’s done in the appropriate context. As a farmer, you obviously understand where the nutrient cycles have been broken, but I don’t think that most of Pollan’s readership has that understanding. Too many people have this idea that manure is a source of nutrients for growing crops and that our farms will be like natural ecosystems if only we raise animals. The point I have attempted to make is that even with animals on the farm we are still breaking the cycle, and that we are at best taking advantage of resources that we wouldn’t have access to without the animals. I don’t claim to have answers, but I think it’s important to give the problem this context.

      You write, “As for Salatin, if the manure he collected from his animals (e.g. from the barn in the winter) were returned to the field growing the grain, it would make even more sense to talk about animals cycling nutrients.” I have not read anything to indicate that this is happening, but even if it were, it would require some data to show that this kind of nutrient cycling should have a place in a sustainable agriculture and that it wouldn’t be better to simply grow less crop and feed it to people.

      Concerning dependency, it seems to me that when Pollan writes, “even more dependent than it already is on fossil fuels and chemical fertilizer,” he intends for the reader to recall his writing on corn in the first part. Nonetheless, you are right that there is more to dependency than simply the amount used, so I will need to post a correction.

      On the subject of fossil fuel use for transportation, it seems to me that, at very least, local food systems could use some improvement there. Transporting things in small quantities can be very inefficient, even if they are not transported very far. Here is one study which found many instances in which more fuel was required to transport products to farmers’ markets than to grocery stores. However, there are probably more efficient distribution systems that could be used for the same local products.

      Finally, you write, “One might even argue that veganism leads to abuses of farm animals, insofar as those abuses are a part of our industrial food system and veganism increases our dependency on that system.” This would surely require more argument than you’ve given. As you’ve presented it, it’s not clear why you could not construct a parallel argument that non-industrial animal farming leads to the environmental abuses of CAFOs insofar as those abuses arise from animal agriculture (which small-scale animal farming promotes).

      • Eric B. said

        Adam, thanks for the thoughtful response. With regards to Salatin, I think we’re pretty much on the same page, also with humanure, although it seems like maybe you’d place higher expectations on farmers than I do. I believe organic principles require complete nutrient cycles, but I also see the need for farmers to work in our present reality, i.e. I see the need to make compromises as we work toward more perfect systems. I use a tractor, for instance, even though I think a mule would be my most organic source of draft power. But with my present circumstances as they are, I wouldn’t be able to make a living with a mule (largely for lack of knowledge), and I believe that the world is more organic with me using a tractor than it would be without. I can see that a lot of grain farmers would be in a similar situation with fertilizer. Consumers are sending so many nutrients to landfills and rendering so many nutrients unfit for for farm use (by diluting with so much water weight, not to mention mixing with all sorts of chemicals and pharmaceuticals), that farmers often have no good organic options for returning nutrients to the land, especially when it comes to expansive crops like grains. So I see this as a valid issue but one for which most of the burden shouldn’t fall on the farmers.

        I see the above as very important reasons for shrinking the scale of farms and supply lines. Complete nutrient cycles will only be possible when supply lines are not only short enough to justify the efficient return of waste products to the farm, but also controlled tightly enough by the community (i.e. in small-scale, non-industrial ways) to prevent those waste products from getting contaminated with things that wouldn’t be good for farmland.

        On another point, I have no doubt that, as you suspect, none of the manure from Salatin’s animals is returned to the land growing the grain. I would agree that lots of things ought to change with Salatin’s model, not just how he uses his animal manure. I would note that Salatin’s model is prominent not because he’s especially organic but precisely because he’s developed a way to make attractive profits mimicking the economics of factory farming while selling his end product for organic prices — that’s why the results of your economic analysis are so unimpressive. However, as to your point, whether “it wouldn’t be better to simply grow less crop and feed it to people,” that strikes me as a kind of top-down, Soviet style industrial solution lacking the local adaptation and flexibility necessary to real organic integrity.

        On a small scale it can make sense to graze small grains once in the early spring (in the grass stage) before they produce the grain crop, to feed the leftover corn fodder to cattle, to let hogs glean whatever is missed in the harvest, to feed the grain with the higher levels of mycotoxins in the wet years to chickens that have higher tolerances, or to have a few chickens to eat the grain that gets spilled on the ground, etc., etc. Those are all ways that grain and grain byproducts can be fed to animals without competing with human food production. And then there are all sorts of other non-grain things (especially grass) that animals can eat without competing with human food production either. The trouble is that it’s just so much cheaper to feed grain when so many of the costs of grain production are charged to the ecosystem and to taxpayers and to future generations, etc., so the profit incentive lies with Tyson and Salatin.

        But even animal products with real integrity can be more economical than vegan alternatives. 20 grams of protein in the form of those cranberry beans you mentioned — thank you for the kind response; I’m interested in selling dry beans, but it’s a more challenging venture for me as a small farmer — would cost about $2.73. Even if you paid $15/lb for very organic beef, you could get your 20 grams for less than the $2.73. (I sell my best, all grass-fed, fully-equivalent-to-organic beef for an average of about $4.65/lb by the quarter or an average of about $5.70/lb in individual packages. That means you could buy hamburger from me for $4/lb or less.)

        As for transportation costs, that was too big a study for me to read in full, at least right now, but I think a few things are often overlooked in those kinds of studies, chiefly that if I weren’t driving an average of 17 miles one-way to a farmers’ market twice each week, I’d probably be commuting about as far to a corporate job 5 days each week, plus making extra trips to the grocery store, etc. Just as important, the mainstream system is obviously going to have economies of scale, but a more local system would also increasingly realize economies of scale if we moved toward it. There are certainly lots of ways direct market farmers could lessen the mileage embedded in their goods, but on the whole I think what seems obvious rightfully is.

        As for what I said about veganism and dependency on the industrial food system, I’m assuming — and this is what I believe — that the only two fundamentally different agricultural models we can choose are the industrial model and the local/agrarian model. I believe the failures of the industrial model with regards to animals and everything else are from a macro-perspective unavoidable in a consumer society. I believe the only realistic systemic solutions will depend on much more direct, close-at-hand accountability. In other words, I believe what Wendell Berry said, “Without a complex knowledge of one’s place, and without the faithfulness to one’s place on which such knowledge depends, it is inevitable that the place will be used carelessly, and eventually destroyed.”

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