Abstract:
A method for processing biomass that includes forming a first pile comprising biomass; inoculating said first pile comprising biomass; circulating a liquid in said first pile; fermenting the biomass in said first pile to produce a carboxylate salt; and extracting at least a portion of the liquid in the first pile and passing said portion of liquid to a second pile comprising biomass, wherein said second pile is operating at a higher carboxylate salt concentration than said first pile.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of U.S. patent application Ser. No. 12/708,298, filed Feb. 18, 2010, which is a continuation application of U.S. patent application Ser. No. 11/298,983, filed Dec. 9, 2005, which claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 60/635,235, filed Dec. 10, 2004. The disclosures of said applications are hereby incorporated herein by reference in their entirety for all purposes. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       BACKGROUND 
       [0003]    1. Technical Field of the Invention 
         [0004]    The present invention relates generally to biomass processing and, more specifically, a system and method for the storage, pretreatment, and fermentation of biomass. 
         [0005]    2. Background of the Invention 
         [0006]    Processing biomass, especially waste biomass, to recover useful substances has been the focus of numerous efforts. Such treatments have used a variety of treatment methods and chemicals depending upon the desired recovery substance. Treatment with lime has been attempted, but usually at temperatures above 60° C. for time frames of only a few weeks to a month. For example, previously issued patents to Holtzapple and Davison use high-temperature lime treatments to enhance enzymatic digestibility. One patent uses hot lime only and another uses hot lime plus high-pressure oxygen. 
         [0007]    The most common methods for making pulp for paper or cardboard are Kraft and soda pulping. However, both of these methods use expensive chemicals and expensive treatment vessels. Additionally, previous methods and treatment systems often require movement of the biomass several times during the entire treatment process, including pretreatment and recovery. 
       SUMMARY 
       [0008]    According to one embodiment of the invention, a system for processing biomass comprises a chamber, a biomass input device, a fluid input device, and a retrieval device. The chamber is defined by at least a bottom, at least one wall, and a cover supported by the at least one wall. The biomass input device operable to deliver biomass into the chamber to form a biomass pile. The fluid input device is operable to deliver fluid into the chamber to the biomass pile. The retrieval device operable to receive fluid from the chamber. 
         [0009]    Embodiments disclosed herein pertain to a method for processing biomass that may include forming a first pile comprising biomass; inoculating said first pile having biomass; circulating a liquid in said first pile; fermenting the biomass in said first pile to produce a carboxylate salt; and extracting at least a portion of the liquid in the first pile and passing said portion of liquid to a second pile having biomass, wherein said second pile may operate at a higher carboxylate salt concentration than said first pile. 
         [0010]    The method may include introducing calcium carbonate into the first pile while said first pile comprising biomass is being formed. The method may also include circulating a liquid in said first pile is performed intermittently. In some aspects, the method may include pretreating the biomass prior to inoculating said first pile comprising biomass, wherein pretreating and fermenting said biomass take place in the same enclosure without transferring the biomass. In further aspects, pretreating the biomass may include introducing into the biomass lime or lime and air. In an embodiment, the air may be scrubbed of carbon dioxide prior to being introduced into the biomass. 
         [0011]    The method of processing may include handling a multiplicity of piles comprising biomass in a round-robin manner. The method may also include regulating the temperature of the circulating liquid in said first pile. In an embodiment, regulating the temperature of the circulating liquid in said first pile may include passing said circulating liquid through a heat exchanger. In some aspects, the method includes controlling the temperature of the biomass in said first pile by regulating the temperature of the circulating liquid in said first pile. 
         [0012]    Other embodiments of the present disclosure pertain to a method of processing biomass that may include the steps of transporting biomass to a chamber to form a biomass pile, the chamber defined by at least a bottom and adjustable cover; transferring a liquid to the chamber; lowering the adjustable cover from a raised position to a lowered position; fermenting the biomass pile in the chamber to produce a carboxylate salt while the adjustable cover is in the lowered position; and extracting at least a portion of the liquid from the biomass pile and passing the portion of liquid to a second pile comprising biomass, wherein said second pile is operating at a higher carboxylate salt concentration than the biomass pile. 
         [0013]    The method may include fermenting the biomass in the presence of an inoculum. In an embodiment, the adjustable cover may be in the lowered position. The method may include supporting the adjustable cover with a pole that has perforations. In an embodiment, transporting the biomass to the chamber to form the biomass pile and transferring fluids to the chamber are carried out through the perforations. In other aspects, lowering the adjustable cover from a raised position to a lowered position may be carried out by a winch located on the pole, where the winch may be attached to the adjustable cover via a cable and releasing the cable to lower the adjustable cover. 
         [0014]    Yet further embodiments of the disclosure pertain to a method for processing biomass that may include forming a first pile comprising biomass; inoculating the first pile; contacting a fluid with the first pile; fermenting the biomass in the first pile to produce a carboxylate salt; and collecting at least a portion of the fluid from the first pile, the fluid comprising at least some of the carboxylate salt, and passing the portion of fluid to a second pile comprising biomass. 
         [0015]    The method may include introducing calcium carbonate into the first pile while said first pile comprising biomass is being formed. In some aspects, contacting the fluid with the first pile may be performed intermittently. In other aspects, the method may include pretreating the biomass prior to inoculating said first pile comprising biomass, wherein pretreating and fermenting said biomass take place in the same enclosure without transferring the biomass. In further aspects, pretreating the biomass may include introducing into the biomass lime or lime and air. 
         [0016]    Certain embodiments of the invention may provide numerous technical advantages. For example, a technical advantage of one embodiment may include the capability to keep pretreators/fermentors at a low cost. Other technical advantages of other embodiments may include the capability to allow pretreatment and fermentation to occur in the same vessel. Yet other technical advantages of other embodiments may include the capability to remove spent solids. 
         [0017]    Although specific advantages have been enumerated above, various embodiments may include all, some, or none of the enumerated advantages. Additionally, other technical advantages may become readily apparent to one of ordinary skill in the art after review of the following figures and description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    For a more complete understanding of example embodiments of the present invention and its advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:  FIG. 1  is a schematic of a system for processing biomass, according to an embodiment of the invention; 
           [0019]      FIG. 2A-2D  illustrate a system for processing biomass, according to another embodiment of the invention; 
           [0020]      FIG. 3  shows a illustrate a system for processing biomass, according to another embodiment of the invention; 
           [0021]      FIG. 4  shows a cutaway view of a system for processing biomass, according to another embodiment of the invention; 
           [0022]      FIG. 5  shows a system for processing biomass, according to another embodiment of the invention; 
           [0023]      FIG. 6  shows a system for processing biomass, according to another embodiment of the invention; 
           [0024]      FIGS. 7A and 7B  shows rigid covers, according to embodiments of the invention; 
           [0025]      FIGS. 8A ,  8 B, and  8 C show a system for processing biomass, according to another embodiment of the invention; 
           [0026]      FIG. 9  shows a system for processing biomass, according to another embodiment of the invention; 
           [0027]      FIG. 10  shows a system for processing biomass, according to another embodiment of the invention; 
           [0028]      FIG. 11  shows a perspective view of a bottom of a chamber, according to an embodiment of the invention; 
           [0029]      FIG. 12  shows a perspective view of a bottom of a chamber, according to an embodiment of the invention; 
           [0030]      FIG. 13  shows multiple screw conveyors at a bottom of a chamber, according to an embodiment of the invention; 
           [0031]      FIG. 14  shows a system for processing biomass, according to another embodiment of the invention; 
           [0032]      FIGS. 15 and 16  show screw conveyors in V-shaped sections, operable to move material towards a conveyor, according to an embodiment of the invention; 
           [0033]      FIG. 17  shows a system for processing biomass, according to an embodiment of the invention; 
           [0034]      FIG. 18  shows a system for processing biomass, according to another embodiment of the invention; 
           [0035]      FIG. 19  shows a system for processing biomass, according to another embodiment of the invention; 
           [0036]      FIG. 20  shows a cone, according to an embodiment of the invention; 
           [0037]      FIG. 21  shows a cone, according to an embodiment of the invention; 
           [0038]      FIGS. 22 and 23  illustrates the use of a jet in conjunction with a cone, according to embodiments of the invention; 
           [0039]      FIG. 24  shows a cone formed in a floor, according to an embodiment of the invention; 
           [0040]      FIG. 25  shows a grate, according to embodiment of the invention; 
           [0041]      FIG. 26  shows an isometric view of a cut-away cone, according to embodiment of the invention; and 
           [0042]      FIGS. 27 ,  28 , and  29  show patterns for cones, according to embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    It should be understood at the outset that although example embodiments of the present invention are illustrated below, the present invention may be implemented using any number of techniques, whether currently known or in existence. The present invention should in no way be limited to the example embodiments, drawings, and techniques illustrated below, including the embodiments and implementation illustrated and described herein. Additionally, the drawings are not necessarily drawn to scale. 
         [0044]    As briefly identified in the Background, processing biomass, especially waste biomass, to recover useful substances has been the focus of numerous efforts. Accordingly, teachings of some embodiments recognize a system and method that converts biomass to carboxylic acids using a mixed culture of microorganisms. Further, teachings of some embodiments of the invention recognize an economical construction of biomass processing systems. Yet further, teachings of some embodiments of the invention recognize a system and methods for integrating pretreatment and fermentation into a single chamber or vessel. Additionally, teachings of some embodiments of the invention recognize a system and methods for removing spent solids from fermenting chambers. 
         [0045]    Particular embodiment may be utilized to process biomass, for example, lignocellulosic biomass and other types of biomass, with lime or other alkali to yield useful recovery products. Other embodiments may be utilize other treatment methods. In addition, in some embodiments, the technology described herein may be utilized in conjunction with the technology described in U.S. patent application Ser. No. 10/698,199, filed Oct. 31, 2003 which is herein incorporated by reference. 
         [0046]      FIG. 1  is a schematic of a system  100  for processing biomass  105 , according to an embodiment of the invention. The system  100  of  FIG. 1  presents example components that may be utilized in such a processing of biomass. For purposes of brevity, the structural details of various components of system  100  are not shown or described. For example, the system may include a cover, which is not shown in  FIG. 1 . Additionally, although specific components are shown with reference to the system  100  of  FIG. 1 , other systems may utilize more, fewer, or different component parts. 
         [0047]    In the embodiment of  FIG. 1 , the system  100  includes a water-impermeable bottom liner  102 , a gravel layer  104 , a drainage device  106 , a perforated pipe  107 , a biomass input device  108 , a lime input device  110 , a calcium carbonate input device  112 , a distribution device  114 , a perforated pipe  115 , a pump  116 , a water supply  118 , an inoculum supply  120 , an air distribution device  122 , a perforated conduit  123 , an air blower  124 , a lime water slurry container  126 , and a heat exchanger  128 . In particular embodiments, the system  100  may be utilized as a multi-use facility, which accepts and stores untreated biomass, pretreats the biomass, and ferments the biomass. Such a multi-use facility in particular embodiments may result in a reduction of biomass handling. 
         [0048]    The liner  102  in particular embodiments may be formed of a water-impermeable material. In operation, the liner  102  supports the gravel layer  104  and prevents water or other materials from entering the ground. The liner  102  may be placed upon any suitable support. In the embodiment of  FIG. 1 , the liner  102  is shown in a pit or bermed wall in the ground. The liner  102  may have any suitable shape and the depth. In particular embodiments, the liner  102  may be designed to handle a desired amount of gravel for the gravel layer  104 . An example depth for gravel layer  104  is approximately three feet; however, other suitable depths may also be utilized for gravel layer  104 . The gravel layer  104  may be comprised of any suitable loose or unconsolidated deposit of rounded pebbles, cobbles, boulders, or other suitable stone-like material that allow water to flow relatively freely therethrough. 
         [0049]    Shown disposed on top of the gravel layer  104  in this embodiment is a pile of biomass  105  that may be delivered over gravel layer  104  via biomass input device  108 . Biomass input device  108  represents any suitable device for creating biomass pile  105 , such as a suitable conveyer system, front-end loader, or other suitable delivery system or device. As described above, the biomass in one embodiment, is lignocellulosic biomass, such as bagasse, corn stover, or other suitable biomass. 
         [0050]    The lime input device  110  and the calcium carbonate input device  112  are any suitable devices operable to deliver lime and calcium carbonate, respectively, to the pile of biomass  105 . In particular embodiments, the lime and/or calcium carbonate may be delivered while the pile of biomass  105  is formed so that the materials are evently distributed throughout. In other embodiments, lime and/or calcium carbonate may utilized to pretreat the biomass. Although the amount of lime added to the pile of biomass  105  may vary depending on the type of biomass  105 , in one embodiment, an amount of lime delivered to the pile of biomass  105  is between approximately 10% and 30% of the biomass by weight. 
         [0051]    Water from water supply  118  may be circulated through biomass pile  105  by pump  116  by delivering the water through distribution device  114 , which may be any suitable device operable to distribute the water to the biomass pile  105 . In particular embodiments, the distribution device  114  may include a perforated pipes  115  while in other embodiments the distribution device  114  may be spray head(s) or other suitable devices. After the water has traveled through the biomass pile  105  and gravel layer  104 , the water is recovered through a drainage device  106 , which may include a perforated pipe  107 . In such an operation, circulation of the water may either be continuous with a relatively low flow rate or may be intermittent with a relatively high flow rate. 
         [0052]    With a continuous circulation and low flow rate, channeling may occur which is undesirable because some portions of biomass pile  105  may not be wetted. Uneven wetting of biomass pile  105  may cause any one or more of the following problems: incomplete pretreatment of the pile of biomass  105 , poor temperature control, and spontaneous combustion of dried portions of the pile of biomass  105 . An intermittent circulation and high flow rate periodically floods the pile of biomass  105 , thus ensuring all or most portions are wetted, thereby overcoming the potential problems of continuous circulation with low flow rate. 
         [0053]    The temperature of the water circulated through the pile of biomass  105  may be regulated with the heat exchanger  128 . The heat exchanger  128  may be any suitable device used to control the temperature of the water circulated through biomass pile  105 . For example, heat exchanger  128  may be a shell-and-tube type heat exchanger designed to offload thermal energy. 
         [0054]    While biomass pile  105  is being pretreated, air may be blown upward through biomass pile  105  to enhance lignin removal by alkaline oxidation. This may be facilitated by air blower  124  forcing air through air distribution device  122 , which may include in particular embodiments a perforated conduit  123  disposed inside the gravel layer  104 . Because air contains carbon dioxide, it may react with lime to form calcium carbonate, an unproductive reaction. To prevent this from occurring in biomass pile  105 , the air may be scrubbed of carbon dioxide by passing it through lime water slurry in container  126 , which may be a suitable packed column or tank. Oxygen enriched air flow may also be used. 
         [0055]    The pile of biomass  105  may be subjected to a fermentation process while disposed over gravel layer  104 . To facilitate the fermentation after pretreatment is complete, water may be circulated through biomass pile  105  that contains an inoculum of acid-forming microorganisms obtained from inoculum supply  120 . The acid-forming microorganism start to degrade pile of biomass  105 , forming carboxylic acids that react with calcium carbonate to form calcium carboxylate salts. Water may then be circulated through the pile of biomass  105  to remove the carboxylate salts. 
         [0056]    The storage, pretreatment, and fermentation of biomass may also be accomplished using other suitable storage facilities or systems. Various embodiments of these systems are described below in conjunction with  FIGS. 2A-29 . The components described with reference to  FIG. 1  may be utilized in conjunction with any of the systems described with reference to  FIGS. 2A-29 . 
         [0057]      FIG. 2A-2D  illustrate a system  200  for processing biomass  205 , according to another embodiment of the invention.  FIG. 2A  shows an isometric view of a portion of the system  200 . The system  200  is similar to the system  100  of  FIG. 1  except that system  200  includes a geomembrane  203 , a cover  232 , support ribs  233 , walls  230 , and a conveyor  209 . As described in further details below, the various components of the system  200  may form a chamber  250  that can be used for storing untreated biomass, pretreating the biomass, and fermenting the biomass. 
         [0058]    The geomembrane  203  may be formed from any suitable material and may perform a similar function to the liner  102  of  FIG. 1 . In particular embodiments, the geomembrane  203  may line a substantial portion of the chamber  250 . The geomembrane  203  in this embodiment is disposed beneath a gravel layer  204  on a bottom portion of the system  200 . The geomembrane  203  lines the interior of the walls  230  and extends over chamber  250  with support from the support ribs  204  to form the cover  232 . 
         [0059]    The walls  208  in this embodiment may be made of concrete. In other embodiments, the walls  208  may be made of other suitable materials. In particular embodiments, the walls  208  may extend above a ground level. In other embodiments, the walls may extend into the ground. 
         [0060]    The support ribs  233  may be any suitable structure that can provide support for geomembrane  203  to help form the cover  232 . For example, with reference to  FIG. 2C , the support ribs  233  are shown as an I-beam. However, the support ribs  233  may also be other suitable structural members such as a lightweight truss. 
         [0061]    The geomembrane  203  may be coupled to the support ribs  233  in any suitable manner.  FIG. 2B  illustrates one embodiment of coupling the support ribs  233  (shown as an I-Beam in this embodiment) to the geomembrane  203 . With reference to  FIG. 2B , one or more bolts  234  are utilized to couple geomembrane  203  to the support ribs  233 . Other suitable fasteners other than bolts may also be utilized to couple geomembrane  203  to the support ribs  233 . A pair of stiffener plates  235  may provide stiffness to geomembrane  203 , which is disposed between the stiffener plates  235  and the support ribs  233  and coupled therebetween by bolts  234 . To prevent the corrosion of the bolts  234  and the stiffener plates  235 , a boot  236  formed from the similar or different material than the geomembrane  203  may be utilized to cover the bolts  234  and stiffener plates  235 . 
         [0062]    The conveyor  209  may operate to dispose the biomass  205  (seen in  FIG. 2D ) on top of the gravel layer  204  in the chamber  250 . The conveyor  209  may be supported by the support ribs  233 , running along the length of the system  200 . 
         [0063]      FIG. 2D  shows a cross-sectional view of the system  200  of  FIG. 2A , illustrating additional details of system  200  according to an embodiment of the invention. Biomass  205  is shown disposed on top of the gravel layer  204  on a bottom portion of the system  200 . A perforated pipe  223  of an air distribution device  222  is embedded into the gravel layer  204  allowing compressed air from the air blower  224  to be blown up through the pile of biomass  205 . Also, a perforated pipe  207  of the drainage device  206  is embedded into the gravel layer  204  to allow liquid to be pumped via pump  216  from the gravel layer  204  into sprayers  215  of distribution system  214  to wet the top of the pile of the biomass  205 . In a manner similar to that described above with reference to  FIG. 1 , during the pretreatment phase, air may be blown up through the pile of the biomass  205  while water is simultaneously trickled through the pile of the biomass  205 . The action of air plus lime (which may be premixed into the biomass pile) removes lignin from the biomass, rendering it more digestible. When the lime is exhausted, the pH drops near neutrality. At this point, an inoculum of mixed acid-forming microorganisms may be added (e.g., using an innoculum supply  120  such as that shown in  FIG. 1 ), which digests the biomass  205  and converts it to mixed carboxylic acids. The acids react with calcium carbonate (which may be premixed into the biomass pile  205 ) to form carboxylate salts. The pump  216  circulates water through the pile of the biomass  205  to help extract the carboxylate salts as they are formed. During the above operations, the circulating liquid may go through a heat exchanger  228  to regulate temperature. Additionally, a portion of the circulating liquid may be passed to an adjacent chamber  250 , which operates as a fermentor, that is operating at a higher carboxylate salt concentration. The circulating fluid may additionally be harvested and processed to recover the soluble product. 
         [0064]      FIG. 3  shows a illustrate a system  200 B for processing biomass, according to another embodiment of the invention. The system  200 B comprises eight-cells or chambers  250 B. For purposes of brevity, the system  200 B is shown in partial view with only particular components shown (e.g., walls  230 B) and some components ghosted. However, each of the cells or chambers  250 B may operate in a similar manner to the chambers  250  of system  200  described above. For example, each of the chambers  250 B may operate to store untreated biomass, pretreat the biomass, and ferment the biomass. Additionally, each chamber  250 B of system  200 B of  FIG. 3  may include similar or different components than system  200 . Further, each of the chambers  250 B may operate as independent systems or systems that communicate with one another. The cells or chambers  250 B may additionally be operated in a “round robin” manner. That is, one of the cells or chambers  250 B would be in the process of filling with fresh biomass while another cell or chamber  250 B would be in the process of removing spent solids. The other six cells or chambers  250 B may be fermenting, each in a successive stage of digestion. 
         [0065]      FIG. 4  shows a cutaway view of a system  200 C for processing biomass, according to another embodiment of the invention. The system  200 C of  FIG. 4  shows how earth-moving equipment can enter a chamber  250 C to remove spent solids in embodiments of the invention. In a manner similar to the system  200 B of  FIG. 3 , the system  200 C of  FIG. 4  is in partial view with only particular components shown and some components ghosted. The system  200 C in particular embodiments may include an elevated slop  297 C, a wall  230 C, a door  298 C, and a slope passage  299 C. 
         [0066]      FIG. 5  shows a system  300  for processing biomass  305 , according to another embodiment of the invention. The system  300  is similar to system  200  of  FIGS. 2A-2D , including a geomembrane  303 , a gravel layer  304 , a pile of biomass  305 , a chamber  350 , an air blower  324 , an air distribution device  322  with a perforated pipe  323 , a conveyor  309 , a drainage device  306 , a pump  316 , a distribution system  314  with sprayers  315 , a cover  332 , a chamber  350 , and a heat exchanger  328 . The system  300  is different in that the system  300  does not include walls and the cover  332  is a rigid cover. The rigid cover  332  in this embodiment is shown with an inner core  338  between an interior layer  338  and an exterior layer  339 . The inner core  338  may be made from a variety of materials, including, but not limited to “papercrete,” a mixture of cement, sand, and paper pulp. The portions of each component of the papercrete can vary, but in particular embodiments includes the following mixture: cement 20%; sand 20%; and paper 60%. In other embodiments, the inner core  338  may be made of a papier mâché, a mixture of paper pulp and glue, or other suitable materials. The advantage of papercrete and papier mâché is that they can contain waste paper, which renders inner core  338  inexpensive. Also, the paper may act as an insulator, which helps regulate the temperature of the biomass pile. Because the paper component can be damaged when wetted, the inner layer  338  and the exterior layer  339  of the rigid cover  332  in some embodiments may be coated with a water-proofing material, such as tar. 
         [0067]      FIG. 6  shows a system  400  for processing biomass  405 , according to another embodiment of the invention. The system  400  is similar to system  300  of  FIG. 5 , including a geomembrane  403 , a gravel layer  404 , a pile of biomass  405 , a chamber  450 , an air blower  424 , an air distribution device  422  with a perforated pipe  423 , a conveyor  409 , a drainage device  406 , a pump  416 , a distribution system  414  with sprayers  415 , a heat exchanger  428 , a chamber  450 , and a rigid cover  432  having an inner core  438  sandwiched between an interior layer  437  and an exterior layer  439 . The system  400  of  FIG. 6  additionally includes a concrete wall  430  surrounding a base of the system  400 . 
         [0068]      FIGS. 7A and 7B  shows rigid covers  432 A,  432 B, according to embodiments of the invention.  FIG. 7A  show a cut-away view of a domed rigid cover  432 A that may be used with a circular chamber  450  and  FIG. 7B  show a cut-away view of an arched rigid cover  432 B that may be used with a rectangular chamber. Because the construction material is very light and could be blown over by the wind, the rigid covers  432 A,  432 B may be secured to the ground using a cable  440 . The rigid covers  432 A,  432 B shown with reference to  FIGS. 7A and 7B  may be utilized with various embodiments of the invention. 
         [0069]      FIGS. 8A ,  8 B, and  8 C show a system  500  for processing biomass, according to another embodiment of the invention.  FIG. 8A  show tent poles  542  for the system  500 . The tent poles  542  are shown protruding from a gravel layer  504 . In this embodiment, the tent poles  542  include pipes  544  at the center with I-beams  546  welded to the exterior of the pipes  544 . A hoop  548  surrounds the pole  544 , which can be raised or lowered using a winch system (seen in  FIG. 8B ), which can pull on cables  547 . The pipes  544  may include perforations  545  at various levels. The perforations  545  allow a biomass pile to be constructed by pumping an aqueous slurry of the biomass through the pipes  544 . In such an operation, the water carries the biomass to the pile and then drains away from the gravel base. The perforations  545  may also be used to circulate water through the pile during pretreatment or fermentation. Also, the perforations  545  may be used to deliver inoculum to the pile when the pretreatment is completed. 
         [0070]      FIG. 8B  shows the tent poles  542  supporting a flexible cover  555 , which is in the low position. The flexible cover  555  may be made of a variety of materials. A bellows  552 , extending from a support  553  provides flexibility as the flexible cover  555  is raised and lowered. In particular embodiments, the bellows  552  may facilitate a substantial enclosure of the chamber  550 . During fermentation, the flexible cover  555  can be lowered onto the biomass pile. A slight vacuum can be applied to the chamber  550  by sucking away fermentation gases. This ensures that the flexible cover  555  is sucked tightly against the pile, which prevents it from being damaged by the wind. 
         [0071]      FIG. 8C  shows the flexible cover  555  in the raised position. The flexible cover  555  can be raised while the pile is being built, or when the solid residues are being removed. In such a raising of the flexible cover  555 , the winch  554  can pull in the cables  547 , which are attached to the rings  548 , which are attached to the flexible cover  555 . 
         [0072]      FIG. 9  shows a system  600 A for processing biomass  605 A, according to another embodiment of the invention. The system  600 A may be similar to system  400  of  FIG. 6 . However, in the system  600 A of  FIG. 9 , fresh water is added via a pump  617 A at the bottom through a distributor system so that it percolates up through the biomass  605 A, which is submerged under a water line  695 A. Fresh biomass  605 A may constantly be added at the top of a chamber  650 A, for example, through a conveyor  609 A or other suitable mechanism and spent biomass may be removed from the bottom, using embodiments described herein or any suitable mechanism. Product with carboxylate salts may be removed from the top at the area indicated by arrow  658 A, using any suitable device. In particular embodiments, a screen  656 A may be employed to keep solids from entering the liquid product stream. A cover  632 A for the system  600 A may be any suitable cover, including rigid covers, flexible covers, and others. Walls  630 A and a floor  631 A may be made from any suitable material, including but not limited to concrete. 
         [0073]      FIG. 10  shows a system  600 B for processing biomass  605 B, according to another embodiment of the invention. The system  600 B is similar to the system  600 A of  FIG. 9  except that the system  600 B has a significant portion of the biomass  605 B located above a first water line  695 B. Liquid may be removed from a second water line  694 B just below a first water line  695 B, heat exchanged with a heat exchanger  628 B to regulate temperature, and pumped via a pump  616 B onto the sprayers  615 B located in a distribution system  614 B of an arched or domed cover  632 B. The spray percolates through the biomass  605 B above the first water line  695 B. Product with carboxylate salts may be removed from the top at the area indicated by arrow  658 B, using any suitable device. Screens  656 B,  693 B may allow removal of liquid while preventing passage of solids. The cover  632 B for the system  600 B may be any suitable cover, including rigid covers, flexible covers, and others. Walls  630 B and a floor  631 B may be made from any suitable material, including but not limited to concrete. 
         [0074]      FIG. 11  shows a perspective view of a bottom of a chamber  650 , according to an embodiment of the invention. The bottom of the chamber  650 , for example, may be the bottom of chambers  650 A,  650 B of  FIGS. 9 and 10 . The bottom of the chamber  650 , which as referenced above may be used as a fermentor, is shown as a series of V-shaped sections  660  with a screw conveyor  662  located at the tip of the V-shaped sections. In one embodiment, the slope of the “V” is greater than the angle of repose, allowing solids to flow toward the top of the V. 
         [0075]      FIG. 12  shows a perspective view of a bottom of a chamber  650 C, according to an embodiment of the invention. To help lubricate the surface and force solids downward towards the tip of a V-shaped section  660 C, the section  660 C may have water distributors  664 C that employ nozzles  666 C that blast liquid downward, forcing the solids downward. 
         [0076]      FIG. 13  shows multiple screw conveyors  662 D at a bottom of a chamber  650 D, according to an embodiment of the invention. The screw conveyors  662  of the embodiment of  FIG. 13  convey spent solids to a side, where another conveyor  663 D removes them for ultimate disposal. 
         [0077]      FIG. 14  shows a system  700  for processing biomass, according to another embodiment of the invention. The system  700  of  FIG. 14  is similar to the system  600 A of  FIG. 9 , including walls  730 B, a floor  731 B, a water line  795 B, a pump  717 , a screen  756 , biomass  750 , product removal indicated by arrow  758 , a cover  732 , and a water line  795 . However, system  700  includes a conveyor  763  that removes solids for ultimate disposal is located at the center of the chamber  750  rather than the side. The conveyor  763  is serviced by screw conveyors  760  on both sides, which is readily seen in  FIGS. 15 and 16 . 
         [0078]      FIGS. 15 and 16  show screw conveyors in V-shaped sections  760 , operable to move material towards a conveyor  763 , according to an embodiment of the invention. 
         [0079]      FIG. 17  shows a system  800 A for processing biomass  805 A, according to an embodiment of the invention. The system  800 A of  FIG. 17  is similar to the system  600 B of  FIG. 10 , including components such as walls  830 A, a floor  831 A, a first water line  895 A, a second water line  894 A, a heat exchanger  828 A, a pump  816 A, a pump  817 A, a first screen  856 A, a second screen  893 A, sprayers  815 A located in a distribution system  814 A, product removal indicated by arrow  858 , and a cover  832 A. However, the system  800 A has a single large cone  892 A at the bottom of the chamber  850 A that collects all spent solids. Further, the pump  817 A pumps into a distribution device  888 A. The biomass  805 A may be introduced into the system using any of a variety of biomass input devices  808 A. And, a conveyor  867 A removes spent solids from the tip of the cone  892 A and conveys them out the top of the cover  832 A. To provide a back-up barrier that would prevent leakage of contents of the chamber  850 A into the groundwater should a leak develop, the floor  831 A and/or wall  830 A that help define the chamber  850 A may be located in a hole  890 A that is filled with a gravel layer  804 A and lined with a geomembrane  803 A. The space between the floor  831 A and/or wall  830 A that help define the chamber  850 A and the geomembrane  803  may be filled with water  891 A, which provides hydraulic head and helps balance the pressure of the liquid inside the chamber  850 A. Such a configuration may allows thinner concrete structures, for example, in the floor  831 A and/or walls  830 A. Additionally, such a configuration may eliminate the need for prestressing the concrete with steel cables that keep the concrete in compression, where it is strongest. 
         [0080]      FIG. 18  shows a system  800 B for processing biomass  805 B, according to another embodiment of the invention. The system  800 B of  FIG. 18  is similar to the system  800 A of  FIG. 17 , including components such as walls  830 B, a floor  831 B, a first water line  895 B, a second water line  894 B, a pump  816 B, a heat exchanger  828 B, a pump  817 B that pumps water into a distribution device  888 B, a first screen  856 B, a second screen  893 B, sprayers  815 B located in a distribution system  814 B, biomass  805 B, product removal indicated by arrow  858 B, a cover  832 B, a cone  892 B at the bottom of the chamber  850 B, a biomass input device  808 B, a hole  890 B, a gravel layer  804 B, a geomembrane  803 B, and water  891 B. However, a conveyor  865 B removes spent solids from the tip of the cone  892 B and removes them from a side of the system  800 B. 
         [0081]      FIG. 19  shows a system  900  for processing biomass  905 , according to another embodiment of the invention. The system  900  of  FIG. 19  is similar to the system  800 A of  FIG. 17 , including components such as walls  930 , a floor  931 , a first water line  995 , a second water line  994 , a pump  916 , a heat exchanger  928 , a pump  917  that pumps into a distribution device  988 , a first screen  956 , a second screen  993 , sprayers  915  located in a distribution system  914 , product removal indicated by arrow  958 , a cover  932 , a hole  990 , a hole  990 , a gravel layer  904 , a geomembrane  903 , and water  991 . Biomass  905  may be delivered to the chamber  950  using a conveyor  909  or other suitable device. The system  900  includes multiple cones  970  for removing spent solids. Each of the cones  970  have a passage  971  at the tip and are supported by concrete ribs  972  extending from the floor  931 . In particular embodiments, a space  973  created by the concrete ribs  972  may be large enough to allow a person to perform maintenance under the cones  970 . In particular embodiments, the space  973  between the ribs  972  may have water circulating so that as solids flow through the cone  972 , they are dispersed into a dilute slurry, which is easily pumped. When the dilute slurry is brought to the surface, the dilute slurry may be sent to a settling tank (not shown), where the solids settle out and the liquid is recovered for recycling back to the space  973 . To help solids flow from the top of the cones  970  to the spaces  973  under the cone, the pressure of liquid circulating in the space  973  may be regulated to be lower than the pressure above the cone  970 . This pressure differential forces the solids to flow through the cone  970  when pressure is applied. To help regulate the pressure in the space  973 , a gas space may be present under the cones  970 , which provides some compressibility. 
         [0082]      FIG. 20  shows a cone  970 , according to an embodiment of the invention. The cone  970  of  FIG. 20  has a check valve  976  that allows solids to flow in only one direction through the passage  971 . In particular embodiments, the check valve  976  may allows solids to be flushed to the space  973  upon application of pressure, for example, a high-pressure liquid or the like. In other embodiments, the check valve  976  may be actuated using a suitable actuator. Upon opening of the check valve  976 , solids may flow through the passage  971  in the direction of arrow  977 . 
         [0083]      FIG. 21  shows a cone  970 , according to an embodiment of the invention. The cone  970  of  FIG. 21  has a pinch valve  978  adjacent a passage  971 . The center  980  of the pinch valve  978  is flexible rubber and the exterior is a rigid housing  975 . When pressure is applied to the space between the rubber center  980  and the rigid housing  975 , for example through opening  979 , the rubber center  980  closes. When pressure is removed from the space between the rubber center  980  and the rigid housing  975 , the pinch valve  978  opens, allowing the flow through the passage  971  in the direction of arrow  977 . 
         [0084]      FIGS. 22 and 23  illustrates the use of a jet  981  in conjunction with a cone  970 , according to embodiments of the invention. In the embodiments of  FIGS. 22 and 23 , a jet  981  is added to the space above the cone  970 . High pressure fluid (e.g., water) exiting the jet  981  forces solids to flow through the passage  971  of the cone  970 , allowing a flow indicated by arrow  977  and preventing blockage. As shown in  FIG. 22 , in particular embodiments the jet  981  may be used in conjunction with a check valve  976 . As shown in  FIG. 23 , in particular embodiments the jet  981  may be used without a check valve  976 . In  FIG. 23 , the pressure above and below the cone  970  (e.g., on each side of the passage  971 ) may be substantially the same. Accordingly, high-speed fluid (e.g., water) exiting the nozzle  981  forces solids to flow through the passage  971  to the space  973  below the cone  970 , where they can be flushed out in a dilute slurry. 
         [0085]      FIG. 24  shows a cone  970  formed in a floor  931 , according to an embodiment of the invention. The cone  970  is formed into the floor  931 , which as described above may be made of a variety of materials, including, but not limited to, concrete. In such a embodiment, a space  973  may shaped as a pipe in the floor  931  below the tip of the cone  970  to allow removal solids in a dilute slurry. To enhance flow to the space  973 , particular embodiments may use a jet  981  to force solids through a passage  971  at the tip of the cone  970 . 
         [0086]      FIG. 25  shows a grate  982 , according to embodiment of the invention. The grate  982  in particular embodiments may be placed in similar location to the cones of other embodiments and operate in similar manner. A rotating set  983  of nozzles  984 , which may spray in a manner similar to a lawn sprinkler, blasts solids from the grate  982  allowing the solids to drop to the space  973  below where they may be mixed into a dilute circulating slurry, which brings the solids to the surface for ultimate disposal. 
         [0087]      FIG. 26  shows an isometric view of a cut-away cone  970 , according to embodiment of the invention. At the tip of the cone is a passage  971 . 
         [0088]      FIGS. 27 ,  28 , and  29  show patterns for cones, according to embodiments of the invention.  FIG. 27  shows a pattern  1001  by which cones  1070  may be laid on the bottom of a chamber that has a rectangular base, according to an embodiment of the invention. 
         [0089]      FIG. 28  shows a pattern  1101  by which cones  1170  may be laid on the bottom of a chamber that has a circular base, according to an embodiment of the invention. 
         [0090]      FIG. 29  shows a pattern  1201  by which cones  1270  may be laid on the bottom of a chamber that has a circular base, according to an embodiment of the invention. The pattern  1201  is shown as a series of concentric cones  1270 . In other embodiments, the pattern may be a spiral of cones. 
         [0091]    Although the present invention has been described with several embodiments, a myriad of changes, variations, alterations, transformations, and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes, variations, alterations, transformation, and modifications as they fall within the scope of the appended claims.