I've been trying to save energy by burning more wood. It's an easy choice: my house is surrounded by trees and if I didn't burn them for fuel I'd have to pay someone to take away the dead ones anyway.
But saving energy also uses energy. Yesterday I was splitting a log with wedge and hammer. I was using a hammer (made in China) to pound a wedge (made in India) to split locally grown wood in order to burn it in my stove (made in Canada). My chainsaw, happily, is a U.S.-made brand, though I expect at least some of its components come from abroad.
How much wood will I have to burn before I've paid the energy cost of moving a 5-pound hammer across the Pacific, a 2-pound wedge halfway around the world, and a 100-pound iron stove across North America? My back-of-the-envelope figures indicate something like 200 million joules to move those items to me. Two hundred megajoules is a lot, right?
Well, no. It's about as much energy as I use to run my computer for three or four months. That costs me about six bucks. The wood I'm cutting has an energy content of about 15 gigajoules per ton. So to make up for the energy used to bring me my tools I have to cut 1/75 of a ton, or 26 pounds of wood. I did that in about half an hour yesterday.
So other than showing off my mastery of basic arithmetic, what does this prove? Simply this: energy is not expensive. For instance, I almost certainly over-estimated the energy used to transport those items, and the cost of that energy, because shipping is very efficient and uses very cheap fuel. But we think of energy as expensive because humans are very inefficient. When I spend an hour cutting logs with a chainsaw it uses something like a quarter of a liter of gasoline. For me to cut those same logs with a handsaw would take days of work and thousands of calories' worth of food.
In other words, the value of energy is related to the value of human time which it replaces. One reason energy prices have been going up globally in recent years is the increasing wealth of societies like China and India, and their increased demand for energy. I pay more for gas because it's no longer worthwhile to pay someone in India to do brute physical labor in place of a machine. His time is worth more now than his energy.
And that is because those workers in India are now working in foundries, making tools . . . like splitting wedges.
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