Exergetic evaluation of corn-ethanol production in China

The cumulative exergetic method is used in this study to identify the renewability of the total corn-ethanol production in China when capturing all natural nonrenewable resources consumed in the integrated process including agricultural crop production, corn transportation, industrial conversion and waste treatment. A modified exergy-based indicator is thereby proposed to quantify the renewability of corn-ethanol production process. For the conditions prevailing in China, the renewability indicator as suggested by Berthiaume et al. is calculated to be -4.58, denoting the production process is highly nonrenewable. In addition, a novel indicator is also presented to reveal the environmental cost-effectiveness of the corn-ethanol process as supplement to the renewability indicator. Finally, the sensitivity analysis shows that the defined system boundaries, electricity-generation structure of the country, and technological constraints and choices of production process influence the renewability evaluation results. (C) 2007 Elsevier B.V. All rights reserved.