Methods of compressing lignocellulosic feedstock into discrete units, and related systems

1. A method of processing lignocellulosic feedstock comprising:

grinding lignocellulosic feedstock to provide ground lignocellulosic feedstock pieces, wherein the ground lignocellulosic feedstock pieces each have a length and a width, and wherein the average length of said ground lignocellulosic feedstock pieces is in the range from 0.25 inches to 12 inches;

and

compressing at least a portion of the ground lignocellulosic feedstock pieces to form a plurality of discrete units, wherein the plurality of discrete units have a bulk density in the range from 4 pounds per cubic foot to 25 pounds per cubic foot as measured by ASAE S269.4.

2. The method according to claim 1 , wherein at least a portion of the ground lignocellulosic feedstock has a moisture content in the range from 10 to 50 percent by total weight of the ground lignocellulosic feedstock.

3. The method according to claim 1 , further comprising contacting the lignocellulosic feedstock and/or the ground lignocellulosic feedstock with and aqueous composition so that at least a portion of the ground lignocellulosic feedstock has a moisture content in the range from 10 to 50 percent by total weight of the ground lignocellulosic feedstock.

4. The method according to claim 1 , wherein the lignocellulosic feedstock comprises hemicellulose and cellulose and further comprising:

contacting the plurality of discrete units with an aqueous composition to hydrolyze at least a portion of the hemicellulose and/or cellulose and form a liquid component and a solid component.

5. The method according to claim 1 , further comprising, before grinding, cleaning the ground lignocellulosic feedstock to remove at least a portion of non-lignocellulosic feedstock material from the ground lignocellulosic feedstock, wherein the non-lignocellulosic feedstock material is selected from the group consisting of dirt, silt, sand, rocks tramp metal, glass, and combinations thereof.

6. The method according to claim 1 , wherein compressing comprises passing the lignocellulosic feedstock through one or more extruder dies to form the plurality of discrete units.

7. The method according to claim 6 ; wherein the one or more extruder dies each have an exit opening shape selected from the group consisting of a square-shaped opening, a rectangular-shaped opening, a circular-shaped opening, and combinations thereof; and wherein the average length of said ground lignocellulosic feedstock pieces is at least 0.5 times the largest dimension of the exit opening shape.

8. The method according to claim 1 , wherein compressing comprises passing the lignocellulosic feedstock through a radial extruding device to form the plurality of discrete units.

9. The method according to claim 1 , wherein the lignocellulosic feedstock comprises corn stover.

10. The method according to claim 1 , further comprising, prior to grinding, unbaling a bale of lignocellulosic feedstock to provide the lignocellulosic feedstock for grinding.

11. The method according to claim 1 , wherein the plurality of discrete units have a Pellet Durability Index of less than 90 as measured by ASAE 5269.4.

12. A system for processing lignocellulosic feedstock comprising:

a source of lignocellulosic feedstock;

a grinding system configured to grind the lignocellulosic feedstock to provide ground lignocellulosic feedstock pieces, wherein the ground lignocellulosic feedstock pieces each have a length and a width, and wherein the average length of said ground lignocellulosic feedstock pieces is in the range from 0.25 inches to 12 inches, and wherein the source of lignocellulosic feedstock is in fluid communication with the grinding system; and

a compressing system configured to compress at least a portion of the ground lignocellulosic feedstock pieces to form a plurality of discrete units, wherein the plurality of discrete units have a bulk density in the range from 4 pounds per cubic foot to 25 pounds per cubic foot as measured by ASAE S269.4, wherein the grinding system is in fluid communication with the compressing system.

13. The system according to claim 12 , further comprising a wetting system coupled to the system for processing lignocellulosic feedstock and configured to apply an aqueous composition to at least a portion of the lignocellulosic feedstock and/or the ground lignocellulosic feedstock.

14. The system according to claim 13 , wherein the wetting system is configured to apply an aqueous composition to at least a portion of the lignocellulosic feedstock and/or the ground lignocellulosic feedstock so that the ground lignocellulosic feedstock has a moisture content in the range from 10 to 50 percent by total weight of the ground lignocellulosic feedstock.

15. The system according to claim 12 , wherein the lignocellulosic feedstock comprises hemicellulose and cellulose and further comprising:

a source of an aqueous composition;

a hydrolyzing system in fluid communication with the compressing system and the source of the aqueous composition, wherein the hydrolyzing system is configured to contact the plurality of discrete units with the aqueous composition to hydrolyze at least a portion of the hemicellulose and/or cellulose and form a liquid component and a solid component; and

optionally, a separating system in fluid communication with the hydrolyzing system and configured to separate at least a portion of the liquid component from the solid component, wherein the separating system comprises at least one screen device configured to retain the solid component while at least a portion of the liquid component passes through the screen device to separate at least a portion of the liquid component from the solid component.

16. The system according to claim 12 , wherein the compressing system comprises an extruder device including one or more extruder dies, wherein the extruder device is configured to apply pressure to at least a portion of the ground lignocellulosic feedstock so that at least a portion of the ground feedstock passes through the one or more extruder dies to form the plurality of discrete units having a bulk density in the range from 4 pounds per cubic foot 25 pounds per cubic foot.

17. The system according to claim 12 , further comprising:

a first cleaning system in fluid communication with the grinding system to receive the ground lignocellulosic feedstock, wherein the first cleaning system is configured to remove at least a portion of non-lignocellulosic feedstock material from the ground lignocellulosic material, wherein the non-lignocellulosic feedstock material is selected from the group consisting of dirt, silt, sand, and combinations thereof; and

a second cleaning system in fluid communication with the first cleaning system to receive the ground lignocellulosic feedstock, wherein the second cleaning system is configured to remove at least a portion of non-lignocellulosic feedstock material from the ground lignocellulosic material, wherein the non-lignocellulosic feedstock material is selected from the group consisting of rock, tramp metal, glass, and combinations thereof, wherein the grinding system is in fluid communication with the second cleaning system.

18. The system according to claim 12 , wherein the lignocellulosic feedstock comprises corn stover.

19. The system according to claim 12 , further comprising:

a source of a plurality of bales comprising the lignocellulosic feedstock; and

an unbaling system that can unbale the plurality of bales to provide the unbaled lignocellulosic feedstock to the grinding system.

20. A system for processing lignocellulosic feedstock comprising:

a source of lignocellulosic feedstock;

a grinding system configured to grind the lignocellulosic feedstock to provide ground lignocellulosic feedstock pieces;

a compressing system configured to compress at least a portion of the ground lignocellulosic feedstock pieces to form a plurality of discrete units, wherein the plurality of discrete units have a bulk density in the range from 4 pounds per cubic foot to 25 pounds per cubic foot as measured by ASAE S269.4, wherein the grinding system is in fluid communication with the compressing system;

a wetting system coupled to the system for processing lignocellulosic feedstock and configured to apply an aqueous composition to at least a portion of the lignocellulosic feedstock and/or the ground lignocellulosic feedstock pieces;

a control system operatively coupled to the system to control the bulk density of the plurality of discrete units to be in the range from 4 pounds per cubic foot to 25 pounds per cubic foot, wherein the compressing system comprises an extruder device having an electric extruder motor, wherein the control system comprises a controller configured to execute program instructions, wherein the controller is operatively coupled to the wetting system and the compressing system to cause the wetting system and the compressing system to perform one or more of the program instructions, and wherein the program instructions comprise:

measuring an ampere value of the electric extruder motor;

determining an amount of aqueous composition to apply to the ground lignocellulosic feedstock based on the ampere value to control the bulk density of the plurality of discrete units to be in the range from 4 pounds per cubic foot to 25 pounds per cubic foot.