So, it was not difficult for me, because I was trained that way from Howard Odum. Also, when I was a graduate student there were a lot of very exciting things going on. Ecologists were much more involved—not just in biodiversity, which is where much of the focus is today, but in dealing with important issues of the relation of humans to resources. Paul Ehrlich [author of The Population Bomb (1968)], Garrett Hardin [known for his 1968 Science paper “The Tragedy of the Commons”], George Woodwell [founder of the Woods Hole Research Center], many other people—these were very influential to me as a graduate student.
For society's energy sources, is it important to consider EROI?
Is there a lot of oil left in the ground? Absolutely. The question is, how much oil can we get out of the ground, at a significantly high EROI? And the answer to that is, hmmm, not nearly as much. So that's what we're struggling with as we go further and further offshore and have to do this fracking and horizontal drilling and all of this kind of stuff, especially when you get away from the sweet spots of shale formations. It gets tougher and tougher to get the next barrel of oil, so the EROI goes down, down, down.
Is there some minimum EROI we need to have?
Since everything we make depends on energy, you can't simply pay more and more and get enough to run society. At some energy return on investment—I'm guessing 5:1 or 6:1—it doesn't work anymore.
What happens when the EROI gets too low? What’s achievable at different EROIs?
If you've got an EROI of 1.1:1, you can pump the oil out of the ground and look at it. If you've got 1.2:1, you can refine it and look at it. At 1.3:1, you can move it to where you want it and look at it. We looked at the minimum EROI you need to drive a truck, and you need at least 3:1 at the wellhead. Now, if you want to put anything in the truck, like grain, you need to have an EROI of 5:1. And that includes the depreciation for the truck. But if you want to include the depreciation for the truck driver and the oil worker and the farmer, then you've got to support the families. And then you need an EROI of 7:1. And if you want education, you need 8:1 or 9:1. And if you want health care, you need 10:1 or 11:1.
Civilization requires a substantial energy return on investment. You can't do it on some kind of crummy fuel like corn-based ethanol [with an EROI of around 1:1].
A big problem we have facing the alternatives is they're all so low EROI. We'd all like to go toward renewable fuels, but it's not going to be easy at all. And it may be impossible. We may not be able to sustain our civilization on these alternative fuels. I hope we can, but we've got to deal with it realistically.
Do you think we're facing limits to growth now?
I think if you correct the U.S. GDP for debt—in other words, the debt is some kind of not-real growth—then I think the GDP hasn't grown at all since 2005. It's just grown through debt. I think clearly growth has declined; it's possible that growth has either stopped or may soon stop.
We know that the middle class has not increased its income now for 20 years. Behind that—not always the immediate cause, but looking over the shoulder of the causes—I find the decline in the availability of energy.
It's terrifying to people—politicians and economists—who base everything on growth. I think they won't talk about it because the concept is terrifying.