The Oil Drum

77 comments on EROEI Short #1: Boundaries & Calculations

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Arlo on August 23, 2007 - 9:09pm

I used to run a synthetic rubber plant that, itself, has a bazillion energy inputs and that's just part of the overall energy picture.But it is possible to determine how much energy it took to make the synthetic rubber polymer and process it so I'd leave it go at that.

First of all, how do you calculate total energy use in complex manufacturing processes? If it's possible to do so, why can't that sort of energy accounting be used as a model for larger systems of production? Unless of course someone wants to include the total background energy radiating throughout the entire universe in the calculations. I don't mean to be facetious but if the usefulness of the ratio EROEI is inversely proportional to the number of inputs one defines into the ratio then it would make sense to keep the number of inputs as limited as possible which raises another question. For what is the ratio useful? Shouldn't the questions be defined more precisely first, for example, what is EROEI in converting shale to oil versus extracting oil from tar sands in terms of natural gas consumed for a given quantity of oil produced? I'm not trying to trivialize an issue being debated by far more capable minds than my own, but it seems analogous to debating the question,"How useful is a spoon?"

Define "useful."

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Todd on August 23, 2007 - 10:18pm

Arlo,

I'm getting frustrated at this point so I'm going to shut up for a while after this post.

The question is, How to define Energy Returned on Energy Invested? That is, how many joules do you get after the conversion or process compared to how many joules it took to run the process including other inputs. It has nothing to do with whether the joules are useful. It has nothing to do with economics.

It is simply joules out versus joules in. Let it go at that without trying to add other considerations or dimensions that aren't germane.

Todd

BTW, a spoon isn't useful because you can "slurp." Nor is a fork since you can use your fingers or a stick. The only thing a knife might be "useful" for is to cut up game. Otherwise, you can knaw.

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Arlo on August 24, 2007 - 1:32am

Todd
I apologize if I came off as a smart-ass. I honestly didn't mean to. The question concerning calculation of energy consumed at the rubber plant you supervised was sincere. If it can be done there, why not on a broader scale? I was looking for insight, not challenging you.

As to the point you raised concerning "usefullness," I wasn't refering to usefullness in any economic sense. So I understand your irritation. I simply meant that if we're going to define EROEI, shouldn't parameters be set based on the nature of the question we're trying to answer. What do we mean when we ask the question,"Is the production of ethanol from sugar more energy efficient than from corn?" Are we asking about the energy used from the point that the sugar or corn begins to be processed or are we asking a broader question about the total energy efficiency of the systems providing trasportation, labor, distribution, etc. My point was that it would seem to make sense to start with the more restricted question and build outward. In other words, the EROEI for the process of converting ethanol from each feedstock is x from sugar and y from corn. Now, add into the ratio energy consumed for production of tractors used on ethanol farms in Brazil and corn farms in the U.S. and the EROEI becomes t from sugar and u from corn. In its narrow sense EROEI would be the most accurate and as the ratio is made more complex by adding layers of inputs it would lose precision but give us information about not just the processing of the fuel but possible comparative advantages in the sense of energy efficiency from one production center to another.

It just seems the debate, which from some of the comments I've read has tried the patience of alot of thinking people, revolves around trying to define the concept without having precisely defined the question.