Expanding Exergy Analysis to Account for Ecosystem Products and Services

Abstract

Exergy analysis is a thermodynamic approach used for analyzing and improving the efficiency of chemical and thermal processes. It has also been extended for life cycle assessment and sustainability evaluation of industrial products and processes. Although these extensions recognize the importance of capital and labor inputs and environmental impact, most of them ignore the crucial role that ecosystems play in sustaining all industrial activity. Decisions based on approaches that take nature for granted continue to cause significant deterioration in the ability of ecosystems to provide goods and services that are essential for every human activity. Accounting for nature's contribution is also important for determining the impact and sustainablility of industrial activity. In contrast, emergy analysis, a thermodynamic method from systems ecology, does account for ecosystems, but has encountered a lot of resistance and criticism, particularly from economists, physicists, and engineers. This paper expands the engineering concept of Cumulative Exergy Consumption (CEC) analysis to include the contribution of ecosystems, which leads to the concept of Ecological Cumulative Exergy Consumption (ECEC). Practical challenges in computing ECEC for industrial processes are identified and a formal algorithm based on network algebra is proposed. ECEC is shown to be closely related to emergy, and both concepts become equivalent if the analysis boundary, allocation method, and approach for combining global energy inputs are identical. This insight permits combination of the best features of emergy and exergy analysis, and shows that most of the controversial aspects of emergy analysis need not hinder its use for including the exergetic contribution of ecosystems. Examples illustrate the approach and highlight the potential benefits of accounting for nature's contribution to industrial activity.

Order from Chaos: A Preliminary Protocol for Determining the EROI of Fuels

“…However, exergy cannot capture many properties of a fuel or energy carrier that contribute to its economic attractiveness, such as transportability, global warming potential, toxicity, or cleanliness [9]. Exergy analyses also ignore important critical inputs such as capital and labor [27]. Economic methods may be able to capture such characteristics.…”

Environmental Comparison of Straw Applications Based on a Life Cycle Assessment Model and Emergy Evaluation

“…The conversion factor called transformity or unit energy value (UEV) is defined as the emergy required to make one unit of a given product or service (Odum 1996). Indices such as the renewability indicator (RI) (Hau and Bakshi 2004), potential greenhouse gas emissions (GHGemitted) (Baral and Bakshi 2010), and emergy per unit money (EmPM) (Brown and Ulgiati 2004), can be used to assess the best use of straw for society and the environment.…”

Advantages and limitations of exergy indicators to assess sustainability of bioenergy and biobased materials

“…CEENE has made a step to integrate renewable resources, but other ecosystem services are still hard to account for. Ecological Cumulative Exergy Consumption (ECEC) proposes to make a link between exergy analysis and the knowledge of ecological processes gained through Emergy analysis (Hau and Bakshi, 2003). Emergy is a different physical metric, and is defined as "the availability of energy of one kind that is used up in transformations directly and indirectly Table 3 Papers investigating the production of bioenergy and biobased production from a life cycle perspective with exergy-based indicators.…”

“…Exergy is being applied as a useful metric in environmental impact assessments (Banerjee and Tierney, 2011;Chen et al, 2009;Hau and Bakshi, 2003;Hepbasli, 2008;Kirova-Yordanova, 2010;Yi et al, 2004). It can account for materials and energy flows alike and can be used for the analysis of complex production pathways (Apaiah et al, 2006;Bakshi, 2000;Huang et al, 2007;Zhang and Chen, 2010).…”