Abstract:
A process and screw in barrel apparatus ( 10 ) for expanding cellulosic materials is described. The expanded cellulosic material is useful as an animal feed and a nutrient source for fermentation processes.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the use of a process and apparatus with a screw in a barrel for treating cellulosic materials in order to expand the materials, thereby making them more useful as animal feeds and for fermentation processes, for instance. In particular the present invention relates to a screw in a barrel process and apparatus which provides continuous processing of the cellulosic material using liquid ammonia which expands the cellulosic material while changing from a liquid to a gas upon exiting the apparatus. 
     DESCRIPTION OF RELATED ART 
     The use of ammonia under pressure to increase protein availability and cellulosic digestibility of a cellulosic containing plant material (alfalfa) is described in U.S. Pat. No. 4,356,196 to Hultquist. The ammonia which is provided in a vessel in liquid form impregnates the plant material and is explosively released upon being exposed to a rapid reduction in pressure in the vessel. The resulting processed material is used for ethanol production or as a feedstock for food or dairy animals. Dale in U.S. Pat. Nos. 4,600,590 and 5,037,663 describes the use of various volatile chemical agents to treat the cellulose containing materials, particularly ammonia, by what came to be known as the AFEX process (Ammonia Freeze or Ammonia Fiber Explosion). The process pressures were somewhat higher than in Hultquist. Holzapple et al in U.S. Pat. No. 5,171,592 describe an improved AFEX process wherein the treated biomass product is post-treated with super heated vapors of a swelling agent to strip the residual swelling agent for recycling. The apparatus  20  has mixing and a staged valve  21  which periodically opens. U.S. Pat. No. 4,644,060 to Chou is of general interest in use of supercritical ammonia to liberate polysaccharides. The patented processes are essentially accomplished on a batch basis. 
     Other prior art references relating to the AFEX process are European Patent No. 0 077 287; Dale, B. E., et al., Biotechnology and Bioengineering Symp. No. 12, 31-43 (1982); Dale, B. E., et al., Developments in Industrial Microbiology, A Publication of the Society for Industrial Microbiology, Vol. 26 (1985); Holtzapple, M. T., et al., Applied Biochemistry and Biotechnology Vol. 28/29, 59-74 (1991); Blasig, J. D., et al., Resources, Conservation and Recycling, 7:95-114 (1992); Reshamwala, S., et al., Applied Biochemistry and Biotechnology Vol. 51/52, 43-55 (1995); Dale, B. E., et al., Bioresource Technology 56:111-116 (1996); and Moniruzzaman, M., et al., Applied Biochemistry and Biotechnology, 67:113-126 (1997). Each of these processes are non-continuous. 
     OBJECTS 
     It is therefore an object of the present invention to provide an improved continuous process for producing an expanded cellulosic material using a swelling agent. It is further an object of the present invention to provide a novel apparatus which is particularly adapted for practicing the process. These and other objects will become increasingly apparent by reference to the following description and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic drawing showing a screw apparatus  10  for the process. 
     FIG. 2 is a side view of an individual screw element  100  showing individual flights  106 . 
     FIG. 3 is an end view of two (2) of the screw elements  100  and  101  acting together along parts of parallel dual shafts  21 . 
     FIGS. 4 and 5 are end cross-sectional views of kneading blocks  200  and  201  in various positions relative to each other which are acting in parallel along parts of dual shafts  21 . 
     FIGS. 6A to  6 I are end cross-sectional views of kneading blocks  200  and  201  of FIGS. 4 and 5 in various relative positions. 
     FIGS. 7 and 8 show cross-sectional and end views of an individual kneading block  200 . 
     FIG. 9 is an end view of a camel screw element  102  which is adjacent to an extrusion die  18  from the apparatus and which forces the cellulosic material into the die block  18  and through die  18 A. 
     FIG. 10 is a side view of the camel back screw element  102  of FIG. 9 which also shows a plug  103  and screw  104  for holding screw element  102  on a rod  105  (which acts as shaft  21  of FIG. 1) supporting the screw elements  100  and  101  and the kneading blocks  200  and  201  along the screw  17 . 
     FIG. 11 is a side schematic view of an extrusion screw showing various screw elements  100  and  101  and kneading blocks  200  and  201  in zones  1  to  7  as set forth in Table 1 hereinafter. 
     FIG. 12 is a side view of a heating and cooling block mounted along the longitudinal axis of the extruder apparatus  10  where {circle around (x)} is water outlet, {circle around ( )} is water inlet and + is an electrical cartridge heater mounted in an opening in the barrel  16 . Table 2 shows the dimensions for the various locations. 
     FIG. 13 is a side view of the die block  18 . 
     FIG. 14 is a top cross-sectional view of the die  18 A. 
     FIG. 15 is a side cross-sectional view of the die  18 A. 
     FIG. 16 is a view looking into the outlet from the die  18 A. 
     FIG. 17 is a graph showing total sugar concentration after enzymatic hydrolysis as a function of time for corn fodders which are treated by the process and apparatus of the present invention and those which are untreated. No die  18 A or die block  18  was used. The extruder apparatus  10  was effective in increasing the total sugar concentration. 
     FIG. 18 is a graph showing glucose as a specific sugar treated in the same manner as in FIG.  17 . 
     FIG. 19 is a graph showing total sugar concentration as a function of time for corn fodders treated by the process and apparatus of the present invention under different conditions. 
     FIG. 20 is a graph showing glucose as a specific sugar treated in the same manner as in FIG.  19 . 
     FIG. 21 is a graph showing total sugar concentration as a function of time for corn fodders treated by the process and apparatus of the present invention under different conditions. 
     FIG. 22 is a graph showing glucose concentration as a specific sugar treated in the same manner as in FIG.  21 . 
     FIG. 23 is a graph showing in vivo digestibility of dry matter in corn fodder in the rumen of a cow as a function of time for various samples. 
     FIG. 24 is a graph showing NDF (Neutral Detergent Fibers) solubles concentration versus time for the samples of FIG.  23 . 
     FIG. 25 is a graph showing hemicelluloses concentration versus time for the samples of FIG.  23 . 
     FIG. 26 is a graph showing cellulose concentration versus time for the samples of FIG.  23 . 
     FIG. 27 is a graph showing lignin concentration versus time for the samples of FIG.  23 . 
     FIG. 28 is a graph showing ash content versus time for the samples of FIG.  23 . 
     FIG. 29 is a graph showing digestion rate as a function of time for the samples of FIG.  23 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The present invention relates to an improvement in a process for expanding a cellulosic material by contacting the cellulosic material with a swelling agent which impregnates the cellulosic material and then rapidly reducing the pressure to thereby expand the cellulosic material by gaseous expansion of the swelling agent, which comprises: (a) injecting the swelling agent and the cellulosic material into a screw in a barrel having a feed throat leading to the screw in rotating contact with the barrel along part of a length of the screw so that the screw is sealed in operation, with an inlet for feeding the swelling agent into the feed throat under pressure to the screw and with an outlet from the barrel adjacent to the screw; (b) compacting the swelling agent and cellulosic material by rotation of the screw in the barrel; (c) removing the swelling agent and the cellulosic material from the barrel through the outlet from the extruder so that the swelling agent expands the cellulosic material; and (d) optionally recovering the swelling agent from the cellulosic material. 
     Further the present invention relates to an improved apparatus with at least one rotatable screw mounted in a barrel with opposed ends, a feed inlet to the screw through the barrel, and a feed outlet from the screw and removal through the barrel, and optional heating and cooling means between the ends of the barrel, which comprises: a liquid inlet to the screw through the barrel intermediate the ends, whereby the liquid is fed to the screw under pressure so that a cellulosic material is expanded or by change of the liquid to a gas upon removal of the cellulosic material from the barrel by the rotation of the screw. 
     The present invention also relates to a system for expanding a cellulosic material which comprises: (a) an apparatus with at least one rotatable screw mounted in a barrel with opposed ends, a feed inlet to the screw through the barrel, and a feed outlet from the screw and removal through the barrel, and optional heating and cooling means between the ends of the barrel, which comprises a liquid inlet to the screw through the barrel intermediate the ends, whereby the liquid is fed to the screw under pressure so that a cellulosic material is expanded upon removal of the cellulosic material from the barrel by the liquid becoming a gas by the rotation of the screw; (b) a liquid supply under pressure to the inlet of the liquid inlet; (c) a confined space in which the system is placed; and (d) gas removal means adjacent the ends of the barrel for removing gas which is released upon expansion of the material. 
     The primary goal of this invention is in the use of a screw and barrel apparatus  10  (shown in FIG. 1) to improve the Ammonia Fiber Explosion (AFEX) Process, which had previously performed only in a batch reactor. Effectiveness of the treatment using the extruder apparatus  10  was defined as an increase in enzymatic or rumen in situ digestibility. 
     EXAMPLE 1 
     The first step was to develop a safe environment in which to work with ammonia. To do this, the Office of Radiation, Chemical, and Biological Safety (ORCBS) at Michigan State University (MSU), East: Lansing, Mich. was contacted. Following their advice, the area around the extruder apparatus  10 , which enclosed the supplemental ventilation units in the room, was completely surrounded with vinyl stripping to contain any ammonia leaks. Testing of this enclosure was done with a smoke bomb that emitted 10,000 ft 3  of smoke in 1 minute, none of which was observed to escape. Additionally, a horizontal fume hood  11  was attached to one of the ventilation ducts to concentrate ventilation immediately around the extruder feed  12  and outlet  13 , as well as the ammonia injection port  14 . Finally, two full-face respirators with removable ammonia cartridges were purchased for use during all experimentation. A safety protocol was developed and reviewed with each person assisting in any experimentation. 
     The extruder apparatus  10  was a Baker-Perkins MPC/V-30 (Saginaw, Mich.) with parallel twin screws  17  side by side, each made up of screw elements  100 ,  101  and  102  and kneading blocks  200  and  201  (FIGS. 2 to  10 ). The motor  15  supplied 3 HP at 500 RPM. The barrel  16  configuration diameter was 30 mm with a length to diameter ratio (L/D) of 10:1. The two (2) screws  17  were co-rotating and self wiping with a variable profile. FIG. 11 shows the position of the segments  100 ,  101 , and  103  and kneading blocks  200  and  201 . Table 1 shows the positions of the elements. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Zone 
                 Element 
                 Length 
               
               
                   
               
             
             
               
                 1 
                 Forward Transport Screw 
                 3 {fraction (13/16)}″ 
               
               
                 2 
                 1 Kneading Block 
                 ¼″ 
               
               
                 3 
                 Forward Transport Screws 
                 1 ¾″ 
               
               
                 4 
                 Mixing Zone 5 Kneading Blocks, ¼″ 
                 1 ¼″ 
               
               
                   
                 each, 5 total, 45° Alignment 
               
               
                 5 
                 Forward Transport Screw 
                 6 ½″ 
               
               
                 6 
                 Kneading Block 
                 ⅛″ 
               
               
                 7 
                 Modified Camel Back Discharge Screw 
                 3 ½″ 
               
               
                   
               
             
          
         
       
     
     The extruder apparatus  10  was supplied with controls (not shown) for both heating and cooling. Heating was supplied by electric cartridge heaters (+ in FIG. 12) in three zones along the barrel  16  and the die block  18 . Cooling was supplied along the barrel  16  length by chilled water fed through cored barrel sections ({circle around (x)} and {circle around ( )} in FIG.  12 ). The dimensions are shown in Table 2. 
     The barrel  16  and die block  18  are heated between about 30° C. to 100° C. along its length. Preferably the die block  18  is heated in this range. 
     
       
         
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Water Inlet 
                 Water Outlet 
                 Heater Locations 
               
               
                   
                 Locations 1 ⅛″ 
                 Locations 1 ⅛″ 
                 1 ½″ above and 
               
               
                   
                 above and below 
                 above and below 
                 below Centerline 
               
               
                   
                 Centerline at: 
                 Center line at: 
                 at: 
               
               
                   
                   
               
             
             
               
                   
                 2 ¾″ 
                 ½″ 
                 3 {fraction (5/16)}″ 
               
               
                   
                 5 ⅜″ 
                 3 ¾″ 
                 4 {fraction (11/16)}″ 
               
               
                   
                 10 ⅞″ 
                 8 {fraction (13/16)}″ 
                 6 {fraction (7/16)}″ 
               
               
                   
                 12 {fraction (15/16)}″ 
                 11 ¾″ 
                 8 {fraction (5/16)}″ 
               
               
                   
                   
                   
                 9 {fraction (5/16)}″ 
               
               
                   
                   
                   
                 11 {fraction (5/16)}″ 
               
               
                   
                   
                   
                 13 {fraction (15/16)}″ 
               
               
                   
                   
                   
                 14 ⅝″ 
               
               
                   
                   
               
             
          
         
       
     
     The die  18 A through which the treated fodder was released, was air cooled. The die block  18  was provided with heaters (+ in FIG.  13 ). All interior surfaces of the extruder apparatus  10  were nitrided with a 63 μ-inch finish which provided excellent corrosion resistance. Screw elements  100 ,  101  and  102  and kneading block  200  and  201  (FIGS. 2,  3 ,  4 ,  5  and  6 A to  6 I) were made of heat treated alloy steel. 
     The corrosion resistance of a single screw element  100 ,  101  was determined prior to any experimentation and no corrosion was observed throughout the experimentation. 
     A reciprocating diaphragm metering pump  50  used to deliver ammonia was an American Lewa (Holliston, Mass.). The pump  50  head was made of  316  Stainless Steel with TEFLON seals. The pump  50  was capable of metering 0.23 to 23.0 GPH. The drive supplied 3 HP. The pump  50  was calibrated with water and the necessary conversions were done to determine the amount of liquid ammonia fed using a specified stroke length and speed setting. 
     All tubing, fittings, and valves used were of 316 SS. The tubing used was ⅜″ OD with 0.065″ walls, rated to 6500 psig. All fittings were rated to the burst pressure of the tubing. The pressure ratings of the materials used are well in the safe range. This was done to insure safety while working with ammonia. Most of the connections were Swagelok fittings, but a few were NPT. A check valve  51  and by-pass valves  52  and  53  were provided. An ammonia tank  54  with a shut-off valve  55  was the ammonia supply. A purge valve  56  was used to clear the system of ammonia. A needle valve  57  was used to meter ammonia into the extruder apparatus  10 . 
     Biomass was fed into the extruder apparatus  10  via the feed tube  20 . A feeder  19  to the feed tube  20  was calibrated by feeding material for a known period of time and determining the mass. Samples that contained different amounts of moisture were calibrated individually. 
     The primary material investigated in this project was corn fodder or stover. The sample material is also referred to herein as biomass. This includes all above ground portions of a corn plant except the grain and cob. 
     Corn fodder was obtained in a large square bale. This material was coarsely chopped using a tractor mounted grinder. The material was then dried (less than 5% moisture) and further milled to pass a 2 mm screen in a rotary knife mill. The size is between about 0.01 inch to 1 inch. The material was stored in plastic bags inside cardboard drums. Water was added in an amount by weight 10% to 80%. Fresh material can be used (usually at about 80% moisture, based upon dry matter weight). 
     The unmodified extruder apparatus  10  had been primarily used for processing of polymers and thus required significant modification. Thus, it was necessary to make several modifications. First, a port  14  was machined to allow the injection of ammonia. The port  14  was approximately half way down the length of the barrel  16 . The port  14  was chosen to maximize the equilibration time of the biomass and ammonia. The equilibration time was approximately one (1) minute, but depended on feed rate, ammonia load, die temperature and the like. The injection port  14  was installed with a Teflon seal to minimize ammonia loss through the port  14 . 
     Second, the screw  17  configuration was modified significantly in an effort to minimize ammonia loss through the feed tube  20 . Additionally, two (2) camel screw elements  102  (one shown in FIGS. 9 and 10) were provided at the discharge end of the screw  17 . Originally these screws were flat on the end. The original design plugged the die block  18 . By building the end of each of the screw  103  into a more conical shape, the biomass was directed into the die block  18  and out through the die  18 A, rather than plugging. 
     The ammonia used was supplied in a 50 lb. cylinder  54  equipped with a dip tube to insure liquid delivery. The pump  50  allowed for control and accuracy in the delivery of ammonia. A check valve  51  was installed just prior to the injection port  14  to maintain the pressure on the ammonia in the tubing after the pump to help insure liquid delivery. Once the pressure generated by the pump  50  reached the cracking pressure of the check valve  51 , the ammonia would flow directly into the extruder apparatus  10 . The reseal pressure was set above the vapor pressure of ammonia to prevent any leakage through the check valve  51 . Several bypass valves  52  and  53  were provided to allow the tubing to be purged by purge valve  56  after use of the extruder apparatus  10  to clean the apparatus. 
     Once it was verified that ammonia and biomass would flow together through the extruder apparatus  10 , increasingly restrictive dies  18  were used. At first, the die block  18  was not used. However, as more confidence was gained, the block  18  was added, as well as die  18 A. Several explosions were obtained with only the block  18  in use, but the enzymatic digestibility of the samples was only moderately higher than the untreated samples. Additionally, the increased pressure generated from a smaller orifice of the die  18 A provided a more effective treatment. 
     Much work has been done on the design of extrusion dies  18 A. However, the biomass mixture is unlike any polymer or food which can be extruded throughout a standard die. Several preliminary dies  18 A were tried with minimal success. These were machined by hand and the rough edges and interior surfaces created problems with biomass flow through the restriction. The die  18 A that proved most useful was machined with a 5° end mill to give a smooth, gradual contraction of 40% of the inlet area (i.e., out let was 60% of the area of the inlet). With this die block  18 , explosions could be consistently obtained. This die  18 A is shown in FIGS. 13,  14  and  15 . The dimensions are shown as follows:                Area                 of                 larger                 Hole     =         π   (     0.5   2     )     2     +       (     1   -   0.5     )        0.5                   =     0.446                   in   2                       Area                 of                 Smaller                 Hole     =       (     0.25   -   y     )          [       π        (     0.25   -   y     )       +   1     ]               x   =       y   tan        5      °               Area                 of                 Smaller                 Orifice     =     0.268                   in   2                              
     The explosions typically came at regular intervals. Some trials showed reproducibility of ±15 seconds. Depending on the ammonia load and temperature, the steady state operation was either continuous or periodic. Higher loads of ammonia (&gt;1.5 mass ammonia/mass biomass) prompted the material to slowly discharge from the extruder apparatus  10  for several minutes and then violently discharge from the die  18 A. Ammonia loads are given in a mass ratio. For example, an ammonia load of 3 signifies 3 pounds (or kilograms, or grams, etc.) of ammonia to 1 pound (or kilograms, or grams, etc.) of dry biomass. Hereafter, ammonia loads are given M/M units, connoting mass to mass ratio. Pressure was observed to build to ˜300 psig, and torque would approach 50%, until the explosion where pressure would drop to 0 psig and ˜11% torque (typical no load value). Alternatively, lower amounts of ammonia (&lt;1.5 M/M) demonstrated continuous minor explosions which was the preferred mode of operation. 
     Other modifications were made as well. For example, TEFLON sheeting was used to minimize extruder pressure loss. It was observed several times that two metal-metal interfaces (the interface of the extruder apparatus  10  and die block  18 , as well as between the die block  18  and the die  18 A) were allowing a portion of the high pressure to escape as evidenced by slight foaming at the interface. The Teflon sheeting (not shown) was cut to fit around the orifice that it sealed and was then installed between the two surfaces. After the installation of these seals, no further foaming was observed. 
     The main parameters varied were temperature and ammonia loading. Water content of the biomass was also varied, but with little success. Moisture content higher than 60% led to the water being squeezed out of the biomass and flowing back to the biomass feed port. Biomass moisture levels are given as the percent of total mass (60% moisture is 60 grams of water in 100 grams of a biomass and water mixture). This created problems with feeding the biomass into the extruder apparatus  10  due to foaming in the feed tube  20  caused by the ammonia. Alternatively, moisture levels lower than 60% did not allow for effective equilibration with the ammonia, and hence, no explosions were obtained. Thus, all trials referred to in the results section were obtained at 60% moisture. 
     Temperature was varied in several ways at zones  1  to  3  of FIG.  11 . Typically, first zone  1 , centered on the biomass feed port, was unheated and cooling was shut off. In this case, heating refers to heating above room temperature. The cooling ability of the first zone was removed because it created condensation around the feed port that led to clogging of the feed. The second zone  2 , at the ammonia injection point  14  was heated slightly, depending on the set point temperature of the die block  18 . Too much heating would vaporize the ammonia and result in a less effective treatment. The third zone  3  was usually heated to a temperature near the average of the set points of the second zone and the die block  18  (FIG.  13 ). The die block  18  temperature was considered the reaction temperature. It appeared that there was an upper bound to the die block  18  temperature, as no explosions were obtained above a set point of 70° C. This is probably due in part to partial vaporization of the ammonia in the third heating zone  3 . The die temperature necessarily caused a temperature rise in the third zone  3  by conductive heat transfer. This leads to an increased amount of ammonia vaporization and a less effective treatment. Additionally, the ammonia can be forced out through the biomass feed tube  20  because of a higher die block  18  temperature. Because the ammonia was not trapped as effectively as desired, the vapor was free to leave the extrusion apparatus  10 . Lower temperature treatments would not generate as high a pressure towards the feed tube  20  and are not as subject to this effect. 
     Ammonia load was the other main parameter varied. The ammonia load was varied from 0.5 to 2.0 M/M. The calculated ammonia load is only an estimation of the actual treatment amount. The extruder apparatus  10  used had a relatively small L/D (10:1, D=30 mm), with a measured barrel  16  length of about 15.25″ and the only practically allowable port  14  for ammonia injection was approximately half way down the barrel  16 . This created some problems with ammonia flowing back through the biomass feed tube  20 . 
     Several efforts were made, by altering the screw  17  configuration, to create a zone of high mixing prior to the ammonia injection port  14  that would effectively provide a plug that would restrict ammonia flow back to the feed tube  20 . The screw elements  100 ,  101  and  102  and kneading blocks  200  and  201  are set forth in Table 2. The first three screw elements  100 ,  101  and  102  were permanently attached to the screw shaft due to the stresses of heating and cooling. These first sections were predominately forward transport screws which typically run at 50% capacity and did not provide an effective restriction. Thus, with a limited amount of the screw shaft available to implement the mixing zone, only five (5) mixing paddles could be used. 
     There were other limitations with regard to the mixing zone. Kneading blocks  200  and  201  are aligned on an individual rod  105  at various angles. When kneading blocks  200  and  201  are aligned at angles from 0 to 90° as shown in FIGS. 6A,  6 B,  6 C,  6 D,  6 E,  6 F,  6 G,  6 H and  6 I, the forward transport of the mixing zone increases as the angle approaches 45° from either direction, and decreases as the angle diverges away from 45°. Angles are determined by looking down the rod  105  from the discharge end  15 , i.e., towards the feed tube  20 . The angle given is the angle of the outermost kneading block  201  to the next one  200  down the shaft  21 . For example, kneading blocks  200  and  201  aligned at 30° have one paddle on the shaft, and the next one rotated 30° clockwise with respect to the previous. At 0° there is no mixing, and at 90° there is maximum mixing. Kneading blocks  200  and  201  aligned at negative angles are reversing and force the flow in the opposite direction. The following table shows the conveyability of the kneading blocks  200  and  201  where F is forward and R is reverse.                           
     Several mixing zone alignments were tried, but most of them were torque limited. In other words, only a small amount of biomass could be fed through the machine before the torque would approach its maximum value. Torque limits are dependent on rotation speed of the dual shafts  21  (supported by rods  105 ). Thus, a 45° mixing zone was implemented. This allowed for a good plug to be formed and also permitted a large flow of biomass. Inspection of the screw elements  100  and  101  after filling showed that the mixing zone prior to port  14  was ˜90% full, while other sections beyond the port  14  were ˜50% filled. Unfortunately, the length of the mixing zone was not long enough to provide a significant restriction for the ammonia vapors. So, some of the injected ammonia was lost through the feed tube  20  due to vaporization. Thus, the actual amount of ammonia used in a treatment is somewhat uncertain, but all runs were categorized by the amount of ammonia injected. 
     EXAMPLE 2 
     Initially, the primary means of quantifying the effectiveness of the process was enzymatic hydrolysis. Since the main goal was to prove the screw in barrel technology for delivering AFEX worked, maximum sugar concentrations were not the focus, but rather relative digestibility. Thus, all samples were hydrolyzed in a pH=4.8 citrate buffer with a cellulase loading of 15 IU/g and a β-glucosidase loading of 1 mL/mL of cellulase. The cellulase used was CELLUCLAST and the β-glucosidase used was NOVO 188, both by Novo Nordisk (Franklinton, N.C. ). All samples were hydrolyzed at 50° C. in an agitated water bath in a 5% (weight) solution for up to 48 hours. The primary analysis took place on a lead HPLC column for glucose, xylose, galactose, arabinose and mannose. Other analyses were done on an acid column which gave glucose and composite sugar peak which consisted of xylose, mannose and galactose concentrations. Finally, a YSI (Yellow Springs, Ohio) instrument was also used and gave glucose concentrations. 
     Use of the die block  18  alone gave an explosion that resulted in total sugar (the sum of the concentrations of glucose, xylose, galactose, arabinose and mannose) concentration after enzymatic hydrolysis for 24 hours of 2.4 times that of completely untreated sample. The glucose concentration of this material was 2.1 times that of the completely untreated material after the same amount of time. The same material gave a total sugar concentration 2.0 times greater than the biomass treated in a screw in barrel apparatus without ammonia and the corresponding glucose concentration was 2.5 times that of the biomass treated in a screw in barrel apparatus without ammonia. Further trials with the die block  18  alone (without die  18 A) gave total sugar concentrations as much as 3.5 times greater than the unprocessed material and 3.4 times greater than untreated material after 24 hours of hydrolysis. 
     The best results obtained with the die  18 A showed a total sugar concentration 2.4 times greater than the completely untreated material after 6 hours of enzymatic hydrolysis. The glucose concentration at this point was 2.3 times greater than that obtained from completely untreated material. 
     In general, the most effective treatments for enzymatic hydrolysis were lower temperature runs. The higher the die block  18  temperature used (greater than 70° C.), the less effective the treatment. This may be due in part to more of the ammonia escaping the apparatus  10  at a higher temperature. However, with a lower temperature, the ammonia will remain in contact with the biomass longer and a more effective treatment is the result. The results of these tests are shown in FIGS. 19 to  22  and Table 3. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Treatment Matrix for In situ Trial 
               
             
          
           
               
                   
                 Sample 
                 Temperature ° C 
                 Ammonia 
                 Moisture 
               
               
                   
                   
               
               
                   
                 A-Untreated 
                 50 
                 N/A 
                 60% 
               
               
                   
                 B 
                 No Heat 
                 1.0 
                 60% 
               
               
                   
                 C 
                 55 
                 1.5 
                 60% 
               
               
                   
                 D 
                 65 
                 0.8 
                 60% 
               
               
                   
                 E 
                 65 
                 1.0 
                 60% 
               
               
                   
                 F 
                 65 
                 1.5 
                 60% 
               
               
                   
                 G 
                 65 
                 1.6 
                 60% 
               
               
                   
                 H 
                 65 
                 2.0 
                 60% 
               
               
                   
                 I 
                 55 
                 1.5 
                 60% 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 2 
     After enzymatic digestibility tests, the ruminant digestibility of the material in an in-situ trial was desired. To accomplish this, several samples were generated with different temperature treatments and ammonia loads. These were taken to the Texas A &amp; M University Animal Science Department (College Station, Texas) and analyzed by in-situ digestibility. Samples were analyzed on a dry basis for weight loss over a known period of time. The material was placed in a small permeable bag of known weight and dried to determine the mass of dry matter. The bags were then placed in the rumen of a fistulated steer. This is a steer that has had a tube surgically inserted that allows access to the animal&#39;s rumen. By removing the bags at specific intervals (0, 3, 6, 12, 24, 48 and 96 hours), thoroughly rinsing and drying, the digestibility of the materials was determined as percent of material weight lost. The weight loss of the material in a specific bag is called the dry matter digestibility, or DMD. 
     An in-situ trial was run. The trial focused on screw in barrel treated materials, with the control being a sample treated at 50° C. with no ammonia. 
     Results of the trial are shown in FIGS. 23 to  29 . The 48 hour digestibility of the trial is tabulated in Table 4. The trial showed that the digestibility of the extrusion treated material at 48 hours was up to 77.4% digestible as compared to the digestibility of 63.0% of the screw in barrel treated but untreated (by ammonia) control. Typical rumen passage time is 48 hours or less. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 48 Hours Dry Matter Digestibility for Trial 
               
             
          
           
               
                   
                 ID 
                 DMD 
                 NH 3 Load 
                 T(° C.) 
               
               
                   
                   
               
               
                   
                 F 
                 77.4 
                 1.5 
                 65 
               
               
                   
                 H 
                 76.1 
                 2.0 
                 65 
               
               
                   
                 C 
                 73.5 
                 1.5 
                 55 
               
               
                   
                 I 
                 73.4 
                 1.5 
                 55 
               
               
                   
                 E 
                 71.6 
                 1.0 
                 65 
               
               
                   
                 G 
                 70.5 
                 1.6 
                 65 
               
               
                   
                 B 
                 70.4 
                 1.0 
                 0 
               
               
                   
                 D 
                 68.0 
                 0.8 
                 65 
               
               
                   
                 A 
                 63.0 
                 0.0 
                 50 
               
               
                   
                   
               
               
                   
                 Notes:  
               
               
                   
                 DMD is the dry matter digestibility, reported as a percent.  
               
               
                   
                 NH 3  Load is the mass of ammonia injected per mass of biomass treated.  
               
               
                   
                 T(° C.) is the Die setpoint.  
               
             
          
         
       
     
     At 48 hours, the effects of temperature and ammonia loading are not extremely clear. The two most effective treatments obtained are at 65° C. with an ammonia load of 1.5 and 2.0 (Samples F &amp; H respectively). The digestibility of F (77.4%) was only slightly greater than H (76.1%). However, Sample G, with an ammonia load of 1.6 M/M and temperature 65° C. was only the  6 th most digestible material, at 70.5%. The third and fourth most effective treatments (Samples C and I respectively) are duplicate samples and show excellent agreement in that they are separated by only 0.05% points and have an average digestibility of 73.5%. Samples I and C were generated at an ammonia load of 1.5 M/M with a temperature of 55° C. Throughout the trial, Samples H and F were consistently the most digestible, with sample H being the most digestible at all time points except 48 and 96 hours. 
     The composition of each material at each time point was determined as well. Assays were used to determine the amount of Neutral Detergent Fibers (NDF), Acid Detergent Fibers (ADF), Lignin and Insoluble Ash. The NDF assay gave the amount of cellulose, hemicellulose, lignin and ash in a sample. The ADF procedure removed the hemicellulose, the lignin procedure removed the cellulose, and the ash procedure removed the lignin. 
     Cellulose and hemicellulose are both considered somewhat digestible while lignin is considered indigestible. Thus, a reduction in apparent lignin content is desired, and this has been achieved. Results show that the lignin content of the samples treated in the apparatus at 65° C. were reduced up to 20.9% as compared to the control which was treated in the apparatus without ammonia, with an average of 11.9% reduction. 
     The rate at which digestion occurs is important as well. In all cases, the initial rate of digestion for all ammonia treated samples was higher than the material treated in the apparatus but without ammonia. In this case, the initial rate of digestion was determined as the rate of digestion between hours 3 and 6. In many cases, the samples gained weight from the 0 to 3 hour samples which does not provide acceptable data. This may be explained by insufficient washing of the 3 hour samples which would leave dust, soluble fractions and microbes trapped in the bag. Another explanation is that the material used to fill the 0 hour bags contained more dust than the 3 hour sample, and would thus allow for more material to be rinsed out. The maximum rate of digestion was 2.25 times that of the control in the trial (untreated control). The maximum observed rate was shown by Sample H at 6.16%/hr. 
     The data also show that both hemicellulose and cellulose fractions decrease over time implying the digestion of these components is occurring. The hemicellulose content of the first trial decreased until 12 hours, rose at 24 hours, then decreased again until test completion. The cellulose fraction rose until 12 hours and then dropped off. This suggests that the hemicellulose is being digested first, until the cellulose is effectively broken down, then the hemicellulose is digested again. As expected, the indigestible lignin concentration steadily increased as the trial progressed. 
     In Examples 1 and 2, the screw in barrel apparatus  10  was used to facilitate the AFEX process. The total sugar yield from enzymatic digestibility of the corn fodder has been increased up to 250%, and the in-situ ruminate digestibility has increased 32% (from 53.8% to 71.2%) over the completely untreated sample. Additionally, the total sugar yield from enzymatic digestibility of the corn fodder has been increased up to 240%, and the in-situ ruminate digestibility has increased 19% (from 63.0% digestible to 77.4%) over the material that was treated in the screw in barrel apparatus with no ammonia. The screw in barrel process also gave results that compare well with the batch process, leading to the conclusion that such a process can be made as effective as the batch process has proven to be. 
     Other results of the trials are encouraging as well. A reduction in apparent lignin is desired and have been achieved with an average decrease of 11.9% (maximum reduction of 20.9% from 8.42% to 6.66%). A high rate of digestion has also been observed. The highest rates of digestion were 2.3 times the rate of digestion experienced by the control used in the respective trials. Finally, the higher level of reduction of cellulose and hemicellulose observed during the trials implies utilization of these constituents. 
     The system of the present invention can be used to recover the gas removed by the hood  11 . Conventional gas (ammonia) receiving is used. This aspect of the present invention is well known to those skilled in the art. 
     Various types of equipment can be used to practice the present invention. Plastics extruders can be modified to practice the invention. Also, pulping defibrillators can be modified to perform the process of the present invention where the screw is in closely spaced contacting relation with a barrel. All of these variations will be obvious to those skilled in the art. 
     It is intended that the foregoing description be only illustrative of the present invention and that the present invention be limited only by the hereinafter appended claims.