Ethanol Economy

Abstract

Abstract In this chapter, the ethanol production processes from various substrates are described. Generally, three types of substrates including sugar-based, starch–based, and lignocellulosic materials have been used for the production of ethanol. Pretreatment of substrate, converting of substrate to ethanol through saccharification and fermentation, and purification of fermentation beer to recover pure ethanol are the overall steps of production processes. Various methods and technologies in each step have been applied. Pretreatment step in the case of lignocellulosic materials is more complicated and contains more process units. A brief overview of global ethanol production and price trends, ethanol use, and main producers and consumers is presented. Economic assessment in terms of production costs and energy ratio is discussed. Detailed energy use contribution in agriculture and bioconversion steps, ethanol production cost breakdown in terms of investment cost, operation costs, substrate costs, and byproducts outcomes and the share of various operation units in the net production cost of ethanol aim at presenting a comprehensive economic assessment. Finally, environmental issues such as emission of greenhouse gases, fossil fuel consumption, acidification, eutrophication and photochemical oxidant formation potential, and human and ecotoxicity impacts of bioethanol produced from various substrates is reviewed and compared with conventional gasoline.