Pretreatment Case Study

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The main objectives of the pretreatment process are to remove lignin and hemicelluloses, increase the porosity of the lignocellulosic materials and reduce the crystallinity of cellulose. Pretreatment should meet the following requirements: - Low capital and operational cost - Effective on a wide range and loading of lignocellulosic materials - Should result in the recovery of most the lignocellulosic components in a useable form in separate fractions - Need for preparation/handling or preconditioning steps prior to pretreatment such as size reduction should be minimized - Avoid the formation of byproducts that are inhibitory to the subsequent hydrolysis and fermentation processes - Low energy demand or be performed in a manner that energy…show more content…
There is not a perfect pre-treatment method employed and remaining bottlenecks include formation of inhibitory products such as acids, furans, phenols, high particle load, high energy input, and efficient separation of soluble sugars from solid residues. Specific pre-treatment conditions are needed for individual feedstocks and mechanistic models can help in the rational design of such processes (Zhang et al, 2009; Eggeman and Elander, 2005). It is particularly important to optimize lignocellulose pre-treatment methods because they are one of the most expensive steps in the overall conversion to bioethanol. Mosier et al (2005) reported that pre-treatment accounts for ~30 US cents/gallon of cellulosic ethanol produced. Pretreatment is needed to change the biomass macroscopic and microscopic size and structure and also submicroscopic chemical composition and structure so that hydrolysis of carbohydrate fraction to monomeric sugars can be obtained more rapidly and with higher yields (Sun and Cheng, 2002; Moiser et al., 2005; Tucker et al., 2003). Pretreatment of cellulosic biomass in cost effective manner is a major challenge of cellulose to ethanol technology research and development. Native lignocellulosic biomass is extremely recalcitrant to enzymatic digestion. Therefore, a number of thermochemical pretreatment methods…show more content…
In combinatorial pretreatment methods, physical parameters such as pressure or temperature or a biological step are combined with chemical treatments and are termed physicochemical or biochemical pretreatment methods. Ammonia fibre/freeze explosion (AFEX) is a good example of a physicochemical method (Sun and Cheng 2002), and Bioorganosolv is a good example of a biochemical method for biomass pretreatment (Itoh et al. 2003). Combinatorial pretreatment methods are generally found to be more effective in improving the biomass digestibility, and are often used in designing leading pretreatment

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