February 17, 2009
The politics of food-7: The energy equation
(This series of posts looks in detail at some of the fascinating aspects of food production identified by Michael Pollan in his book The Omnivore's Dilemma (2006). All page numbers refer to that book, unless otherwise noted. Other related posts can be found here.)
One of the disturbing things about the industrial food chain system is its extensive use of energy, in the form of fertilizer and for transport. But in addition, the use of agricultural crops as animal feed also results in heavy energy use.
When corn is fed to chicken or a cow, 90 % of its energy is lost to bones, feathers, or to staying alive, so by eating corn-fed animals rather than corn directly, we have a factor of ten loss in energy efficiency. There is a pretty standard rule of thumb that for each rung you go up the food chain, you lose a factor of ten in energy. So if you eat an animal or fish that has itself eaten another animal or fish that ate plant food, you have gone two steps up the chain from the original plant source of energy and thus only 1% of that plant's energy comes to you. So, all other things being equal, getting one's calories from plants is the most efficient, which is why environmentalists urge people to eat 'low on the food chain'.
The reason that grain is fed to animals is that despite the energy inefficiency incurred, grain is cheap and animals gain weight about four times faster than they do if they are fed just grass. Every day, a corn fed steer converts 32 pounds of feed into four pounds of gain in the form of muscle, fat, and bone. (p. 80) Only half of that four pounds is in the form of edible meat. (p. 115) For chickens, two pounds of feed converts to one of meat.
But in addition, there is a lot of energy consumed in the food transportation system. For example, a one-pound box of pre-washed lettuce contains 80 calories of food energy. But "growing, chilling, washing, packaging, and transporting that organic salad to a plate on the East Coast takes more than 4,600 calories of fossil fuel energy." (p. 167) "Only a fifth of the total energy used to feed us is consumed on the farm; the rest is spent processing the food and moving it around." (p. 183) This is part of the reason that the 'locavore' (or 'localvore') movement, that encourages people to eat food grown locally, is gaining ground as can be seen in this article by Selena Simmons-Duffin.
The use of fertilizers has, while increasing corn yield, had a negative impact on energy efficiency. Before the advent of chemical fertilizer, corn farms "produced more than two calories of food energy for every calorie of energy invested." Now "it takes more than a calorie of fossil fuel energy to produce a calorie of food." (p. 46)
Furthermore, the use of corn to feed animals results in huge amounts of land being deforested just for this purpose, with negative impact on the contributions to greenhouse gases.
[I]f the sixteen million acres now being used to grow corn to feed cows in the United States became well-managed pasture, that would remove fourteen billion pounds of carbon from the atmosphere each year, the equivalent of taking four million cars off the road . . . as much as a third of all greenhouse gases that human activity has added to the atmosphere can be attributed to the saw and the plow. (p. 198)
It is the availability of cheap energy that has enabled the extensive use of fertilizers and massive worldwide food transportation networks that can produce food at lower direct cost than that grown on sustainable farms locally, although the indirect costs to the environment and health is greater. But with the rise in oil prices, the balance may shift in favor of local sustainable farms.
POST SCRIPT: Israel and Palestine
Two good analyses of the current state of affairs in the Middle East by Noam Chomsky and Norman Finkelstein, who both rip through the official media narrative of the reasons for the appalling treatment by Israel of the Gazans in particular and the Palestinians in general, and get to the heart of the real reasons for that treatment. Well worth reading.