I do wonder. The generally proposed solution to all these problems here on TOD is to switchover the whole economy to zero EROI. See all the links to "limits to growth" etc.

So I wonder how one can think about this
1) clearly, we should not complain about "low" EROI if our solution involves (maximum) zero EROI or even negative EROI. Zero or negative EROI is obviously not a solution for "low or negative EROI" problems (ie. peak oil).
2) using as an assumption that there aren't any (reasonable) limits to growth (or at least none that will prevent the human race from advancing) *ever*

Personally I think I like option 2.

Huh?

No growth does not equal zero EROI. The latter would mean death. Even a 1:1 EROI (no net gain) would not support a steady-state economy. On the other hand, no finite energy source, even with 100:1 EROI, can support endless growth.

I see it here all the time: some people cannot disconnect the concepts of exponential growth and merely being alive. All biological organisms use energy, and thus require energy sources with EROI>1, and they all grow for a while as young individuals, and their populations fluctuate, but they all have zero long-term growth in any given finite environment. Like it or not, the planet it finite and our "economy" is a subsidiary of "the environment".

Maybe a helpful concept here is entropy. (Or maybe not...) basically, to maintain our current state of order, we need a net energy input, so EROI has to be greater than 1. Same goes for any biological system. Many people also seem to forget that that net energy input that allows us to exist and defy the second law of thermodynamics comes from one place only: the sun.

Many people also seem to forget that that net energy input that allows us to exist and defy the second law of thermodynamics comes from one place only: the sun.

You're correct, except that we don't "defy" the 2nd Law. We extract free energy from sunlight down its gradient thru glucose to CO2, H2O & heat, according to the 2nd Law. All these proponents of EROEI analysis seem bound & determined to ignore the sun. Thank you for reminding them where the energy comes from.

for all practical purposes that lead to real or perceived darwinian fitness, energy comes from the ground (in concentrated ancient sunlight form), the biomass (somewhat concentrated old sunlight) and of course current sunlight. Under the Maximum Power Principle as evolved organisms we will grab as much power as we can (collectively). If the current sunlight isn't enough - no problem use the concentrated stuff. On human time scales, that stuff is all FREE (after subtracting energy and resources costs to get it)

Circa 1973 there were several articles in the business and scientific press on the hydrogen economy. One was in Scientific American titled The Hydrogen Economy. I believe that it was the January issue. If memory serves a major theme was that hydrogen could be produced using nuclear or solar energy and used for transportation. There were of course major problems which were discussed. I was more interested in a minor theme, the epithermal concentration of minerals. As I recall it was postulated that the earth was heated primarily by gravitational collapse with an additional input from radioactive sources. As the earth cooled minerals were concentrated by epithermal deposition as they precipitated under various degrees of heat and pressure. The resulting concentration of copper, silver etc. was essentially an enormous gift of low entropy. How does one account for this gift?

This debate that keeps coming up on the earth as a closed vs open system as it relates to net energy has its merits. We're certainly not going to be importing fuel from Mars, but the sun exports massive amounts of free energy to us every day, nearly all of which we waste. If we had electrical lines running from umpteen billion acres of solar panels running all our drilling rigs and electric cars, net energy would be a moot point. A similar argument is made by Huber and Mills in their thought provoking book "The Bottomless Well: The Twilight Of Fuel, The Virtue of Waste, And Why We Will Never Run Out Of Energy". Here they point out that energy does not get used up - it merely changes forms. We just need to get more chemically clever about capturing energy as it changes forms. This cleverness ultimately would be limited only by the 2nd Law of the earth's closed system, and not even by that if you consider the sun.

But it's also true that for all practical purposes, energy comes from the ground. We don't have umpteen billion acres of solar or the chemical cleverness Huber and Mills envision and won't anytime soon. But we certainly will be running up against all the net energy problems very soon.

Thomas Edison seemed to have a handle on all this way back in 1931. He said in a conversation with Henry Ford on the rush into oil:

We are like tennant farmers chopping down the fence around our house for fuel when we should be using Nature's inexhaustible sources of energy - sun, wind, and tide,...I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait untill oil and coal run out before we tackle that.

All these proponents of EROEI analysis seem bound & determined to ignore the sun.

My own impression is that the Solar Source of Earth's energy is mentioned with extreme frequency. Where have you been keeping yourself?