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79 <br />We -at Stra <br />Catalyst <br />Enzymes <br />Storage and <br />Preparation <br />Pretreatment <br />Cellulose Enzimatic <br />Hydrolisys <br />Fermentation <br />Steam <br />Yeast <br />Figure B -12. Process Flow of the BCyL Biomass Ethanol Plant" <br />2. Hydrolysis <br />The cellulose molecules are composed of long chains of sugar molecules. In order to <br />break the cellulose down into sugars, the hydrolysis process is employed. There are <br />two major cellulose hydrolysis processes: <br />a) Acid hydrolysis - dilute acid may be used under high heat and high pressure, <br />or more concentrated acid can be used at lower temperatures and pressure. A <br />decrystalized cellulosic mixture of acid and sugars reacts in the presence of <br />water to complete individual sugar molecules (hydrolysis). <br />b) Enzymatic hydrolysis - uses several enzymes at various stages of this <br />conversion and has the advantage that lignocellulosic materials can be <br />hydrolyzed with relatively mild processing conditions, which avoids the <br />formation of byproducts that would otherwise inhibit enzyme activity. <br />These have been utilized singly or in combination to break the cellulose chains into <br />free sugar, which is fermented for alcohol production. <br />14 Source: Abengoa Bioenergy <br />GBB/C08027 -01 B -16 August 15, 2008 <br />