An Alternative to EROI to Determine Feasibility


As of December 14, 2008, this section is subsumed by the newer paper “EROEI as a Measure of Feasibility” or “EROEI* as a Measure of Feasibility” both of which are posted at

Let us engage in a final thought experiment:   A group of people representing all of the trades and professions wishes to support itself completely by relying on a single alternative, renewable energy technology for all of its energy needs.  Let us suppose further that all of the natural resources necessary to do this are available within a circumscribed area that we shall refer to as the Autonomous Alternative Energy District (AAED) [and the repositories of such natural resources must be retained at steady state from the detritus of the AAED including superannuated installations of the technology].  Nothing is imported from outside the District whereas energy and only energy is exported.  If a man needs a car to drive from his home (in the District) to his job (in the District), the car is built, maintained, and fuelled in the District.  If his wife is sick the doctor in the District will treat her with medicine made in the District from chemicals produced there from raw materials mined there.  The EROI of the new energy technology is the total energy produced, ER, divided by the quantity ER minus the quantity EX, where EX is the energy exported; i. e., EX = ER – EI.  If the District is able to export any energy at all the EROI ratio exceeds one and the technology is feasible – at least.  In this thought experiment, the methodology whereby the sum of all capital costs and operating costs, both direct and indirect, is multiplied by the ratio of Total Energy Budget to Gross Domestic Product will be perfectly accurate as illustrated on any of the spreadsheets associated with this study by pasting cells DP31:DP34 into DO31:DO34 and reading off the ratio of change in energy calculated to change in energy estimated in DO30 by this method.  The answer will be exactly 1.0.

The actual situation in the US economy would be virtually identical to our thought experiment if the economy were to run exclusively on the alternative, renewable energy technology under investigation.  Thus, every ancillary and indirect expense of producing energy including the support of the workers and their dependents and the contributions of fractional persons distributed throughout the economy must be counted in computing energy invested if the EROI methodology is to be used to determine feasibility.  If a thorough accounting of all indirect energy costs, however derivative, cannot take place, the analyst might just as well use the technique discussed in this paper – provided, of course, that the monetary costs are available.  In the case of a stand-alone solar or wind facility that has been offered for sale along with a maintenance contract as in the analyst will have the monetary costs well in hand without a clue as to the energetic costs despite the many excellent papers that do conventional EROI analysis.  For example, Pimentel and Patzek and, more recently, Patzek have worked mightily to defend the low EROI they have calculated for the production of alcohol from corn grown by industrial agricultural methods; however, as I understand their work, they have not included the ancillary costs associated with commerce in America, which are certain to lower the EROI ratio catastrophically.

We may study feasibility in terms of a balance inequality for each experiment such that the energy produced is either less or greater than the energy required by the economy, which includes the energy required by the energy technology under investigation (ETUI).  It is easy to avoid recursion because, for an experiment wherein more energy is produced than consumed, one may assume that scaling back production will not increase the overhead.  Thus, sustainability will have been established.  It is not possible to avoid iterations as I discussed in Chapter 2 of  These iterations always converge because the world is finite and the economy is perforce bounded.

The energy produced is easily calculated by assuming that all of the primary energy in the economy is produced by the ETUI or ETUIs.  Now, if the energy produced is less than the total energy budget of the economy, the ETUI (or the matched slate of ETUIs) is infeasible for the economy under investigation.  Until one finally gets to the experiment wherein the matching problem has been solved (optimized) for an entire slate of ETUIs, we are not investigating a realistic economy.  We optimize the matching technology using standard mathematical optimization.

As stated above, in a Mark II Economy, every converged solution balances Energy Returned with Total Energy Budget; therefore, I have not attempted to model feasibility by computing an energy budget that is less than the energy produced by an alternative energy technology under consideration.  However, impracticality occurs at a much higher EROI than does strict infeasibility which is not so important in the real world as I had imagined previously.  A much more ambitious program to study feasibility using a balance equation (or inequality) approach is described in Future Work. 

Thomas L Wayburn

Houston, Texas

July 16, 2006

Revised July 5, 2010