Happy to see a website devoted to the (mostly) good ideas of Robert Ayres. As the originator of the term if not the concept of EROI I would like to clarify a few things from my own perspective. The energy invested is usually and appropriately considered the energy diverted from society to get energy to society. Thus natural gas used to pressurize an oil/gas field or energy used in society to make a drill bit or oil rig or fertilizer for corn-based ethanol would be considered part of the investment. Geological energy to make radioactive uranium or oil would not.
Energy used to give meaning to worker’s paychecks is debatable but important. Analyses are traditionally done at the wellhead/farmgate etc but can be done downstream. They should not be done for conversion efficiencies alone, such as conversion in a thermal plant, as EROI is meant for energy sources. I am not as hung up on exergy as Bob. Perhaps important in theory, but what we invest and divert is oil, electricity etc. (which can be corrected for quality if appropriate). The Murphy and Hall protocol is a good place to start, and I have just submitted to Springer a manuscript on EROI in biological and economic systems. I believe that discussion on these issues is healthy.
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About the author:
Charles A.S. Hall is an American systems ecologist and ESF Foundation Distinguished Professor at State University of New York in the College of Environmental Science & Forestry.
Hall’s research interests are in the field of Systems ecology with strong interests in biophysical economics, and the relation of energy to society. His work has involved streams, estuaries and tropical forests but focused increasingly on human-dominated ecosystems in the US and Latin America. His research reflects his interest in understanding and developing analyses and computer simulation models of the complex systems of nature and humans and their interactions. Halls focus has been on energy as it relates to economics and environment. His focus is studying material and energy flows referred to as Industrial ecology, and applying this perspective, to attempting to understand human economies from a biophysical rather than just social perspective. (WP)
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