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The oil we eat

Harper's Magazine periodically publishes older content on their Web site. They just put up a good article from a few issues back called "The Oil We Eat." In it, Richard Manning discusses the conversion of energy into different forms of matter: sunlight and oil in fertilizers into carbohydrates in plants, oil in farm equipment into harvested plants, harvested plants into protien in animals ...

There are quite a few assertions, all of them interesting, some of them possibly unreliable. Here are a few excerpts:

Iowa is almost all fields now. Little prairie remains, and if you can find what Iowans call a “postage stamp” remnant of some, it most likely will abut a cornfield. This allows an observation. Walk from the prairie to the field, and you probably will step down about six feet, as if the land had been stolen from beneath you. Settlers’ accounts of the prairie conquest mention a sound, a series of pops, like pistol shots, the sound of stout grass roots breaking before a moldboard plow. A robbery was in progress.

A functioning grassland prairie produces more biomass each year than does even the most technologically advanced wheat field. The problem is, it’s mostly a form of grass and grass roots that humans can’t eat. So we replace the prairie with our own preferred grass, wheat. Never mind that we feed most of our grain to livestock, and that livestock is perfectly content to eat native grass. And never mind that there likely were more bison produced naturally on the Great Plains before farming than all of beef farming raises in the same area today.

Green eaters, especially vegetarians, advocate eating low on the food chain, a simple matter of energy flow. Eating a carrot gives the diner all that carrot’s energy, but feeding carrots to a chicken, then eating the chicken, reduces the energy by a factor of ten. The chicken wastes some energy, stores some as feathers, bones, and other inedibles, and uses most of it just to live long enough to be eaten. As a rough rule of thumb, that factor of ten applies to each level up the food chain, which is why some fish, such as tuna, can be a horror in all of this. Tuna is a secondary predator, meaning it not only doesn’t eat plants but eats other fish that themselves eat other fish, adding a zero to the multiplier each notch up, easily a hundred times, more like a thousand times less efficient than eating a plant.

In the 1940s we got about 100 barrels of oil back for every barrel of oil we spent getting it. Today each barrel invested in the process returns only ten, a calculation that no doubt fails to include the fuel burned by the Hummers and Blackhawks we use to maintain access to the oil in Iraq.