Pretreatment Technologies for Lignocellulose-to-Bioethanol Conversion

Publisher Summary This chapter focuses on pretreatment technologies for lignocellulose-to-Bioethanol conversion. The selection of an appropriate pretreatment determines the process configuration requirements for hydrolysis and fermentation as each step has a large impact on all subsequent stages. The chemistry of the pretreatment has a remarkable importance due to its impact on the global ethanol production process. Furthermore, pretreatment also affects the cost of the following operational steps, that is, downstream cost by determining fermentation toxicity, enzymatic hydrolysis rates, and enzyme loading as well as fermentation process variables. Each technology has advantages and disadvantages and an appropriate pretreatment will not only depend on the technology itself. While biological pretreatments are advantageous because of its low-energy consumption, mechanical comminution is very energy intensive. CO2 explosion is shown as a cost-effective pretreatment; on the other hand, ozonolysis is not economically feasible due to the high cost of the large amount of ozone needed. Acid pretreatment generates high concentration of toxic compounds, but after wet oxidation only low amounts are detected. It is very difficult to conclude an ideal pretreatment and combination of different pretreatments could also be considered and might be interesting to obtain optimal fractionation of the different components and reach very high yields.