Emergy

Emergy is the amount of energy consumed in direct and indirect transformations to make a product or service.

Emergy accounts for different forms of energy and resources (e.g. sunlight, water, fossil fuels, minerals, etc.)

[3] Evolution of the theory by Howard T. Odum over the first thirty years is reviewed in Environmental Accounting[1] and in the volume edited by C. A. S. Hall titled Maximum Power.

After 1986, the emergy methodology continued to develop as the community of scientists expanded and as new applied research into combined systems of humans and nature presented new conceptual and theoretical questions.

The maturing of the emergy methodology resulted in more rigorous definitions of terms and nomenclature and refinement of the methods of calculating transformities.

Using emergy, sunlight, fuel, electricity, and human service can be put on a common basis by expressing each of them in the emjoules of solar energy that is required to produce them.

Energy flows per unit time (usually per year) are presented in the table as separate line items.

References for each of the citations in this table are given in a separate list at the end of this article The concept of emergy has been controversial within academe including ecology, thermodynamics and economy.

[citation needed] The stated goal of emergy evaluations is to provide an "ecocentric" valuation of systems, processes.

Thus it does not purport to replace economic values but to provide additional information, from a different point of view.

[29] Others have rejected the concept as impractical since from their perspective it is impossible to objectively quantify the amount of sunlight that is required to produce a quantity of oil.

In combining systems of humanity and nature and evaluating environmental input to economies, mainstream economists criticize the emergy methodology for disregarding market values.