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Mankind's prosperity has been dependent on availability of affordable energy in the recent centuries. Today, the need of sustainability requires precise energy efficiency evaluation. Unfortunately, the traditional metrics like energy return on investment (EROI) suffer from the system boundaries and from the inability to describe labor and physical capital in terms of energy. Therefore, they tend to omit up to 50% of input energy consumption. The price of energy model (PERM) and cost of energy model (CERM), derived via matrix description of production process, show that the ratio of the average energy input cost to the average useable energy output cost describes energy efficiency completely. The same holds for the ratio of energy prices, if shares of aggregate rents, taxes and subsidies in the input and output prices are similar. The above price (cost) ratio can serve as an EROI check and eliminate the need for a lengthy process analysis. The results enable the extension of energy efficiency metrics by social and environmental effects, measurable mostly in monetary terms. [ABSTRACT FROM AUTHOR]

To consider the environmental impacts of energy resource exploitation and better estimate the energy return of investment (EROI), this paper establishes a new emergy-based method (EmEROI) that can capture the essence of energy resource exploitation. The EmEROI method treats environmental impacts and labor as particular forms of energy, and all forms of energy can be quantified by solar transformity, which is expressed in emjoules as a common unit. The Daqing oilfield is used as an example, and the corresponding EmEROI value is calculated via the proposed method. The results are then compared with standard EROI estimates. Our EmEROI result is much lower than the standard EROI result and presents a more pronounced declining trend. Our results also indicated that the EmEROI estimates conform well to actual conditions and are not as affected by industrial energy intensity levels as the standard EROI. Thus, EmEROI has the potential for use as an integral aspect of energy resource exploitation project evaluations. [ABSTRACT FROM AUTHOR]