Why Emergy- and Exergy Analysis are non-commensurable methods for the assessment of energy conversion systems

The paper discusses a fundamental incompatibility between Emergy- ('EMA') and Exergy ('EXA') Analysis. Both approaches quantify the resource consumption of physical systems by applying space- and time integrated energy input/output methods. A detailed theoretical analysis and two specific examples show that at least one of the claims made by EMA practitioners is based on a misinterpretation of the exergy accounting practices, that the claim that "emergy is embodied exergy" is inconsistent with EMA procedures, and that if these procedures were amended to correctly account for exergy flows, EMA would resemble Szargut's Cumulative Exergy Content method and/or Extended Exergy Accounting.