Quantifying the environmental performance by exergy-based indicators

Over the last three decades environmental issues have a direct impact on technology assessment and policy decisions. One of the difficulties with measuring environmental performance is lack of consensus on evaluation of relevant aspects, including materials and energy use, air emissions, solid and hazardous waste and water pollution. In practice various environmental indicators are used, usually restricted to one specific aspect. In case of complex environmental metrics, such as Life Cycle Analysis, more environmental aspects are involved but they are usually judged in a subjective way. This Chapter presents development aspects of environmental performance indicators based on exergy. The concept exergy is based on the second law of thermodynamics and is very suitable for assessment of various systems, ranging from chemical and energy processes through economic sectors to entire societies. Traditionally, exergy-based indicators are restricted to measurement of thermodynamic efficiency. Recently, they are coupled with Life Cycle analyzes concepts, such as Cumulative Exergy Consumption (CExC). Finally, exergy indicators are extended with environmental and economic issues, as applied in Extended Exergy Accounting (EEA). EE indicators can be expressed in monetary as well as energy units. However, they are sensitive to capital conversion factors, which can be evaluated for various levels, including individual technologies, economic sectors, and entire societies.