EROEI of at least 10:1 to Sustain Civilization

EROI of ultra-deepwater Gulf of Mexico: 4:1 to 7:1

Moerschbaecher, M. 9 July 2011. Ultra-Deepwater Gulf of Mexico Oil and Gas: Energy Return on Financial Investment and a Preliminary Assessment of Energy Return on Energy Investment. Sustainability 2011, 3, 2009-26.


Someone named Memmel posted this on theoildrum. He makes the case that 40 to 50% of us have jobs that somehow relate to food, in some way or another supporting the 1-2% who do the actual farming.

So once EROEI drops below 10 or 15:1 you have collapse.

To be clear: by negative EROEI I mean negative vs the needs of the society. This happens well before EROEI drops to 1:1 or less.  I’d suggest it depends on the complexity of the society. Simpler societies can probably get away with very low EROEI’s since simplicity simply means most members of society are themselves involved in energy and food procurement.

I’ve tried using the concept of the typical support pyramid for a core industry to calculate the minimum EROEI. The idea is that you take a key industry, say for example, farmers, and determine how many people are needed to directly support the modern farmer. The simple calculation of how many people are involved in actually planting and harvesting that leads to and assertion that 1-2% of the population are farmers is simply bullshit. It does not include the gene engineers at Monsanto or the fertilizer or tractor manufacturers, nor does it include the prepared food industry, grocery stores, etc.

My best guess is at least 30% of the population is indirectly involved in the food industry — from frozen foods to actual farming. We changed the nature of the work, but I’d argue it has not really fallen from its low of 40%, just the work has changed from direct planting. On top of this, you have additional support industries such as housing for those in the food industry and cars and doctors etc. Everyone uses a very generic set of services regardless of what the core industry is that creates the initial wealth — which could add another 10-20% to the total and bring the number of people that make a living off of food up close to 50% of the population.

So if everyone else supported the energy and other commodity industries like metals, you need at least a 2:1 EROEI to break even. Of course outside of food, the rest of the various core industries have their own support pyramids and I’d guess that they are 10% each. This leads to a ballpark figure of 10:1 for the minimum energy industry direct EROEI before the society structure as a whole is negative. You can cut down my estimate for food, but I worked pretty hard at it and was surprised how much of the worlds economy is directly and indirectly related to supplying food. And I don’t think it’s wrong. And even if I’m off its easy to imagine that other industries can certainly command a bigger part of the economic pie then I’ve allocated. The bottom line is you can come up with about 10:1 or 15:1 repeatedly using various estimates of our support pyramid for our modern economies. If I’m right and your paper is right (Charles Hall on minimum to sustain Civilization as we know it), and we have dropped into the 3-5:1 range, then one would expect that the economy would fall into a collapse rivaling the Great Depression in magnitude.

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