My colleague Gary Gardner raised the issue of EROIs yesterday; here’s another two cents.
Everyone knows that it takes money to make money, but the same rule applies to a far more important commodity: energy. It takes energy to get energy. This idea is summed up in an increasingly important measure called the energy return on investment (EROI).
EROI reflects the fact that energy isn’t free. Even wind and sunlight, which are available for nothing, can’t be harnessed effectively without some sort of technology—whether it’s as simple as a bit of cloth hung from a boat’s mast, or as complex as a huge hydroelectric facility, a windfarm, or a solar photovoltaic panel array. It takes energy to make the mast, the dam and its generators, the turbines, or the PV panels—sometimes vast amounts of energy. EROI is the ratio of the energy captured and made available by the hardware over its lifetime to the energy required to build, install, and maintain (and, sometimes, to decommission) the hardware.
Why is this important? Because civilization runs on the surplus energy—what’s left over after we build, install, and maintain the hardware.
For most of human history, EROIs were very low, because there were no technologies (apart from a few waterwheels, windmills, and sailing ships) capable of extracting and using the stored energy in coal, oil, natural gas, uranium, sunlight, water, or wind. Civilization ran mostly on human and animal muscle power, and most of that was used just to grow the crops that fed the people and draft animals. The surplus energy was scant.
The industrial revolution changed all that. The invention of machines that ran on coal, (and then oil), and could be used to extract more coal and oil, unleashed a torrent of surplus energy. EROIs soared. As the table to the right (copied from this post to The Oil Drum) suggests, early in the oil age—the heyday of “gusher” fields like Spindletop in Texas—it took only 1 unit of energy to extract 100 units of energy.
Those days are gone, probably forever. Oil’s EROI is declining. Coal’s EROI is still pretty good, but coal is an environmental disaster. Big hydroelectric dams also have good EROIs, but the best sites have already been tapped and the dams have serious ecological problems of their own (including, often, significant greenhouse gas emissions). And while it’s absolutely critical to transition to renewable sources of energy such as wind and solar, their EROIs are not nearly as favorable. The surpluses we’ve become accustomed to will not be available. Energy will be scarcer and more expensive. Some people think this means economic transformation, because the globalized economy that brings American consumers blueberries from Argentina and bottled water from Fiji will contract sharply when transport costs rise. And since industrial agriculture depends heavily on cheap energy, food prices will probably increase as well.
There is a host of fascinating ramifications to this possibility. For now, suffice it to say that lunch was never free, but it might become more expensive than we like.