I had hoped to be posting my review of The Omnivore’s Dilemma by now, but I’ve been a bit sidetracked by a calculation that’s just been begging to be done.
Michael Pollan writes that Polyface Farm produces what looks “an awful lot like the proverbially unattainable free lunch” (127). I’ve pointed out before that Polyface does use feed grains from other farms. What I want to look at is how Polyface’s animal product output might compare to using those grains to feed people. Because of the quality of the data, this calculation will unfortunately be only back-of-the-envelope quality, but I hope that it will still have some value.
I’ll first look at the grain used to feed Salatin’s broilers. The most recent printing of The Omnivore’s Dilemma states (page 222) that Salatin raises 12,000 broilers each year. (The productivity numbers in earlier printings were different. In fact, my copy even has different numbers in two different places.) According to Salatin’s Pastured Poultry Profit$, the broilers have a carcass weight of 4 pounds, and the chickens require 3 pounds of feed for each pound of carcass weight (page 185). That comes out to 144,000 pounds of feed each year. Salatin writes that he uses a feed consisting of 52% corn, 29% roasted soybeans, 11% crimped oats, and the rest consisting of fish meal, kelp and nutritional supplements. Since I’d like my estimate of the energy content of the feed to be conservative, I’ll ignore the calorie content of everything but the grains. Unfortunately, I wasn’t able to find good data for calorie content of feed grains, so I’ll be using data for food-grade grains. Using USDA data for corn, soy, and oats, one finds that a mixture of 0.52 pounds of corn, 0.29 pounds of soybeans, and 0.11 pounds of oats contains a little over 1700 calories. That comes out to 244,800,000 calories in the feed grain.
Now what about the productivity of Salatin’s farm? Here things get pretty tricky. There are several different kinds of animals, and each has several different kinds of meat with different calorie densities. For rabbits, I wasn’t able to find any useful data on carcass weights. Regardless, here is the calculation in tabular form. (References are at the end of the post. Where no reference is given, the source is the version of The Omnivore’s Dilemma available on Google Books.)
|Food||Quantity||Energy density||Total Energy (Cal)|
|Beef||25,000 lb||1163 Cal/lb 1||29,075,000|
|Pork||50,000 lb||1062 Cal/lb 1||53,100,100|
|Broiler hens||48,000 lb 2||615 Cal/lb 1||29,540,136|
|Stewing hens||2,400 lb 3||615 Cal/lb 4||1,476,000|
|Turkeys||12,000 lb5||541 Cal/lb 1||6,492,000|
|Rabbits||5,000 lb 6||617 Cal/lb 7||3,085,000|
|Eggs||360,000 eggs||135 Cal/egg 8||48,600,000|
With these very rough estimates, it appears that Polyface actually requires more calories in feed than it produces in food. As I’ve said, these estimates could be off, but I’ve tried to choose them to be favorable to Polyface. For the output, I’ve used energy data from David and Marcia H. Pimentel, which seems to be higher than USDA data for lean meats. (Pastured meat advocates like to say that grass-fed meat is lower in fat than grain-fed meat.) Also, I haven’t even attempted to consider grains fed to the turkeys, the pigs, or the layer hens, but this is likely substantial as well.
If it were the case that there were more energy in the feed grain than in the farm’s output, that would considerably weaken the environmental case for eating meat from a place like Polyface. While I’m still inclined to believe that Polyface meat is far better than factory-farmed meat, Pollan would have us believe that it’s environmentally better to eat Polyface meat than to eat grains because Polyface’s pastures capture solar energy that we wouldn’t otherwise be able to use. That would not make so much sense, though, if Polyface didn’t actually decrease the amount of grain we needed to grow.
One might argue that because Salatin’s cattle don’t eat grain, Polyface grass-fed beef is still relatively low input. But Pollan has made it very clear that each animal has important roles on the farm. The chickens, in particular, are responsible for fertilizing the pasture. Without the chickens and their feed, some other form of fertility would need to be imported from off the farm.
Because I’ve only done a rough calculation, I’m willing to believe that a more careful calculation might show that Polyface actually does produce more calories in food than it requires in grain feed. I welcome any efforts to tear this analysis apart or explain why it is irrelevant. Nonetheless, I think this rough calculation suggests, at least, that the Polyface meal is further from the “proverbially unattainable free lunch” than Pollan has told us. The question remaining is whether it is further from the free lunch than a plant-based meal.
1 David Pimentel and Marcia H. Pimentel. Food, Energy, and Society, Third Edition. Page 70, Table 8.3.
2 Based on 12,000 broilers (as stated in The Omnivore’s Dilemma) with carcass weight of 4 pounds (as stated in Pastured Poultry Profit$).
3 Based on 800 stewing hens (as stated in The Omnivore’s Dilemma) with carcass weight of 3 pounds (as stated in Pastured Poultry Profit$).
4 Unfortunately, I was not able to find a figure for the energy density of stewing hen meat, so I have assumed that it is the same as broiler hen meat.
5 Based on 800 turkeys (as stated in The Omnivore’s Dilemma) with carcass weight of 15 pounds (as stated in Pastured Poultry Profit$).
6 Here, I’ve had significant difficulty finding data. Pollan tells us that Polyface raises 500 rabbits. I’ve assumed a live weight at slaughter of 20 pounds because that seems very large. I’ve also taken into account that dressed weight is typically about 50% of live weight.
7 Based on USDA data for a composite of cuts.
8 This is another somewhat arbitrary number. I’ve chosen this number to be 150% of the USDA figure for a jumbo egg since Polyface eggs are supposedly richer than most.