Exergetic evaluation of the renewability of a biofuel

Abstract

A method is described to quantify the renewability of a biofuel, namely ethanol produced from corn. In the presentation, the ideal CO₂–glucose–ethanol cycle is considered to show that exergy can be potentially produced through the harnessing of natural thermochemical cycles. Then exergy accounting is used to evaluate the departure from ideal behavior caused by non-renewable resource consumption through the concept of restoration work. This procedure leads the authors to propose a renewability indicator. The different cycles and processes involved in ethanol production from corn are described. Based on the renewability indicator calculated for the overall process, for the conditions prevailing in Quebec, Canada, ethanol production is seen to be not renewable.