(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’.