What is "emergy"

n. (context ecology English) the total energy used in the life cycle of some product; the available energy of one kind that has to be used up directly and indirectly to make a product or service(reference-book year=2001 first=Howard T. last=Odum coauthors=Elisabeth C. Odum title=A Prosperous Way Down, Principles and Policies id=ISBN=0-87081-610-1 pages=67).

Emergy is a type of energy ( exergy) that is consumed in direct and indirect transformations needed to make a product or service. Emergy is a measure of quality differences between different forms of energy. Emergy is an expression of all the energy used in the work processes that generate a product or service in units of one type of energy. Emergy is measured in units of emjoules, a unit referring to the available energy consumed in transformations. Emergy accounts for different forms of energy and resources (e.g. sunlight, water, fossil fuels, minerals, etc.) Each form is generated by transformation processes in nature and each has a different ability to support work in natural and in human systems. The recognition of these quality differences is a key concept.