Thermodynamic Analysis Of Corn Fuel Ethanol Life Cycle System

The research and application of bioethanol as a substitute for automobile fossilfuels had received great attention in many countries. In recent years, the research,production and utilization of fuel ethanol mostly produced from corn have begun tobe impelled in China. However, the life cycle system of corn fuel ethanol must bedriven by both solar energy and fossil energy, and the later inevitably generatesgreenhouse gas and other pollutants emissions. Thus studies on energy balance,carbon budget and renewability issues for corn fuel ethanol have great significancefor the establishment and sustainable operation of this bioenergy generating scheme.The main objective of this thesis is to quantify the sustainability of fuel ethanol fromcorn in China, and analyze its influential factors on the basis of life cycle analysisprinciples from the point of view of thermodynamics.1. The methodology and model of net energy analysis for corn fuel ethanol aredeveloped on the basis of life cycle analysis principles and the first law ofthermodynamics. For prevailing conditions of corn farming, ethanol productionand energy sources structure and so on in China, energy efficiency of corn fuelethanol is estimated and its influential factors are analyzed. It is shown that cornfuel ethanol has certain net energy gains in China, and energy consumption ofdistillation and dehydration process in ethanol production, nitrogen fertilizerproduction and electivity and diesel used in corn farming have been identified asthe most important factors that influence energy benefits of corn fuel ethanol.2. The methodology and model of carbon balance analysis for corn fuel ethanol aredeveloped on the basis of life cycle analysis principles. Following the energybalance analysis of corn fuel ethanol, the amount of net carbon emissions of thecorn fuel ethanol life cycle system is further calculated and its most influentialfactors have been identified. It is shown that the total greenhouse gas emissions inthe overall life cycle of corn fuel ethanol presents negative effect as comparedwith gasoline, but it is possible to achieve, to some extent, positive effect if someimprovements could be made where carbon emissions are mostly generated in thecycle (i.e. ethanol conversion and nitrogen fertilizer using).3. Based on the life cycle analysis principles, the renewability of corn fuel ethanol inChina is quantified by the exergy-based thermodynamic analysis method, and itsinfluential factors are analyzed. It is shown that the industrial corn fuel ethanolcycle presents non-renewability in China, and main reasons for this are stillenergy consumption of ethanol conversion process and the amount of nitrogenfertilizer used in corn farming. So, the technical and thermodynamical perfectiondegree of the cycle must be enhanced to improve the renewability of corn fuelethanol in China.