Ammonia fiber explosion

Ammonia Fiber Explosion Treatment of Corn Stover... 

Index Entries Ammonia fiber explosion corn stover enzymatic hydrolysis simultaneous saccharification and fermentation moisture content residence time. 

Effects of Ammonia Fiber Explosion Treatment on Activity of Endoglucanase from Acidothermus cellulolyticus in Transgenic Plant... 

Ammonia fiber explosion (AFEX) is another physicochemical pretreatment in which lignocellulosic materials are exposed to liquid ammonia at high temperature and pressure for a period of time, and then the pressure is swiftly reduced. A typical dosage is 1-2 kg ammonia/kg dry biomass at 90 °C and residence time of 30 min. To reduce the cost and protect the environment, ammonia must be recycled after the pretreatment. 

AFEX [Ammonia Fiber Explosion (or Expansion)] A pretreatment process for ligno-cellulose prior to enzymatic conversion to ethanol. The wood is exposed to liquid ammonia at 60 to 100°C for a short time, and the pressure suddenly released. Invented in 1998 by B.E. Dale and M. Moniruzzaman at Texas A M University and further developed by Dale at Michigan State University. In 2006, AFEX was regarded as the leading nonenzymatic biomass pretreatment process. 

Com stover used for this study was harvested in 2003 at the Kramer Farm in Wray, Colorado. The stover was pretreated either in-house at the National Renewable Energy Laboratory or received via subcontract fiom the CAFI [12] pretreatment group members. The samples selected for this study were pietreated by alkaline peroxide (NREL), sulfite steam explosion (UBC), ammonia fiber explosion (MSU), and dilute sulfuric acid (NREL) methods. The composition of the pretreated stover was determined by a two-stage sulfuric acid hydrolysis treatment according to the NREL Laboratory Analytical Procedure titled Determination of Stmctural Carbohydrates and Lignin in Biomass [13]. The pretreatment conditions and compositional information for each substrate are listed in Table 2. 

The pretreatment of any lignocellulosic biomass is cmcial before enzymatic hydrolysis. The objective of pretreatment is to decrease the crystallinity of cellulose which enhances the hydrolysis of cellulose by cellulases (17). Various pretreatment options are available to fractionate, solubilize, hydrolyze and separate cellulose, hemicellulose and lignin components (1,18-20). These include concentrated acid (27), dilute acid (22), SOj (25), alkali (24, 25), hydrogen peroxide (26), wet-oxidation (27), steam explosion (autohydrolysis) (28), ammonia fiber explosion (AFEX) (29), CO2 explosion (30), liquid hot water (31) and organic solvent treatments (52). In each option, the biomass is reduced in size and its physical structure is opened. Some methods of pretreatment of Lignocellulose is given in Table I. 

Explosion method Steam explosion, CO explosion, ammonia fiber explosion... 

Hasan, A. Teymouri, F. Laiveimo-Perez Dale, B.E. Ammonia Fiber Explosion Process (AFEX) A Rapid and Flexible Laboratory Scale Unit. 24 Symposium on Biotechnology for Fuels and Chemicals, Spring 2002. 

A variety of methods have been demonstrated for biomass deconstruction. These can be broadly classified as chemical, biological, physical, and physicochemical [155]. Chemical methods include steam, lime, liquid hot water, ionic liquids, organosolve, ammonia, oxidative delignification, and ozonolysis [150, 155]. Physical and physiochemical methods include milling, steam explosion (autohydrolysis), ammonia fiber explosion (AFEX), microwave, extrusion, pulsed electric field, pyrolysis, and ultrasound. Consistent with the theme of this chapter, the first description of a novel non-enzymatic biomass deconstruction technique demonstrated the effectiveness of this method by producing ethanol [156]. 

Ammonia fiber explosion 55 Fermentation feed handling... 

In order to implement the process steps into the Aspen Plus simulator, the stoichiometric reactor unit was used when the process involved a reaction system, and the flash unit was used for the LIME and ammonia fiber explosion (AFEX) pretreatments (in which there are no reactions). The operation conditions specified in these units, for each process, are shown in Table 2.6. 

Steele, B., S. Raj, J. Nghiem and M. Stowers (2005). Enzyme Recovery and Recycling FoUowing Hydrolysis of Ammonia Fiber Explosion-Treated Com Stover. Twenty-Sixth Symposium on Biotechnology for Fuels and Chemicals. B. H. Davison, B. R. Evans, M. Finkelstein and J. D. McMillan, Humana Press 901-910. 

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