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 Amazon.com 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).
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.