Low temperature and low pressure process for agricultural feedstock preparation

Abstract

Methods and systems for preparing agricultural residue or other agricultural feedstock for use as a pulp. The method includes providing non-wood agricultural residue (e.g., corn stover) or other agricultural feedstock that includes agricultural fibers, chemically pulping the agricultural fibers in a preliminary alkaline chemical pulping process at a low consistency and at a low temperature to produce partially pulped agricultural fibers, such step including separating lignin and hemicellulose from the partially pulped agricultural fibers, introducing the partially pulped agricultural fibers into a first reactor, wherein the first reactor operates at a low temperature of less than 100° C. (e.g., 65° C.), introducing the agricultural fibers from the first reactor into a second reactor, where the second reactor operates at a low temperature, of less than 100° C. (e.g., 94-96° C.), the second reactor operating at a higher temperature than the first reactor, to produce pulped agricultural fibers.

What is claimed is: 
     
         1 . A method comprising:
 providing non-wood agricultural feedstock material that includes agricultural fibers, and reducing a size of such agricultural fibers to a desired length, and mechanically refining such agricultural fibers;   chemically pulping the agricultural fibers in an alkaline chemical pulping process to produce an agricultural fiber pulp, wherein chemically pulping the agricultural fibers is achieved at a temperature of less than 100° C. and unpressurized conditions throughout the entire chemical pulping process, without addition of any acids or enzymes, and wherein the method is performed without use of ozone, and without any bleaching; and   introducing the agricultural fiber pulp into a molded pulp product manufacturing machine to make as molded pulp product from the agricultural fiber pulp.   
     
     
         2 . The method of  claim 1 , wherein the pulped agricultural fibers are present as fiber bundles including 2 to 20 fibers. 
     
     
         3 . The method of  claim 1 , wherein the molded pulp manufacturing machine performs at least one of wet pressing or thermoforming of the agricultural fiber pulp to form the molded pulp product. 
     
     
         4 . The method of  claim 3 , wherein the molded pulp product comprises at least one of an egg carton, a molded disposable “paper” plate, a food container, or a molded pulp product used for packaging consumer goods, wherein the molded pulp product is a disposable single use product. 
     
     
         5 . A product, comprising the molded pulp product formed by the method of  claim 1 . 
     
     
         6 . The product as recited in  claim 5 , wherein the product comprises at least one of an egg carton, a molded disposable “paper” plate, a food container, or a molded pulp product used for packaging consumer goods, wherein the molded pulp product is a disposable single use product. 
     
     
         7 . The product as recited in  claim 5 , wherein the product comprises a single use food container. 
     
     
         8 . The product as recited in  claim 5 , wherein the molded pulp product comprises at least one of a waterproofing agent or a sizing agent. 
     
     
         9 . The method of  claim 1 , wherein reducing the size of the agricultural fibers to a desired length and mechanically refining such fibers occurs during or after chemical pulping. 
     
     
         10 . The method of  claim 1 , wherein chemically pulping the agricultural fibers includes chemically pulping with a sodium hydroxide or other active alkali concentration of from 4 g/L to less than 40 g/L, or an active alkali (relative to the agricultural feedstock material) value of from 5% to 30%, for a period of time of from 30 minutes to 5 hours, at a temperature of less than 100° C. 
     
     
         11 . The method of  claim 1 , wherein the molded pulp product includes 10% to 100% by weight of agricultural fibers. 
     
     
         12 . The method of  claim 1 , wherein reducing the size of such agricultural fibers to a desired length, and mechanically refining such agricultural fibers in preparation for pulping comprises hammermilling the agricultural fibers. 
     
     
         13 . The method of  claim 1 , wherein chemically pulping the agricultural fibers in the alkaline chemical pulping process is achieved using a liquor that consists essentially of water and caustic. 
     
     
         14 . The method of  claim 1 , wherein the non-wood agricultural feedstock comprises at least one of corn stover, hemp, wheat straw, rice straw, soybean residue, cotton residue, switchgrass, miscanthus, DDGS, bamboo, or sugarcane bagasse. 
     
     
         15 . A method comprising:
 providing non-wood agricultural feedstock material that includes agricultural fibers, and reducing a size of such agricultural fibers to a desired length, and mechanically refining such agricultural fibers, wherein such agricultural fibers comprise corn stover;   chemically pulping the agricultural fibers in an alkaline chemical pulping process to produce an agricultural fiber pulp, wherein chemically pulping the agricultural fibers includes chemically pulping with a sodium hydroxide concentration of from 4 g/L to less than 40 g/L, or a sodium hydroxide active alkali (relative to the agricultural feedstock material) value of from 5% to 30%, wherein chemically pulping the agricultural fibers is achieved at a temperature of from 60° C. to 99° C. and unpressurized conditions, wherein chemically pulping the agricultural fibers is achieved without addition of any acids or enzymes; and   introducing the agricultural fiber pulp into a molded pulp product manufacturing machine to make a molded pulp product from the agricultural fiber pulp.   
     
     
         16 . The method of  claim 15 , wherein chemically pulping the agricultural fibers is achieved in a 2-step cooking process, comprising:
 introducing the agricultural fibers into a first reactor, wherein the first reactor operates at a low temperature of less than 100° C., and where the agricultural fibers are processed in a first caustic concentration; and   introducing the agricultural fibers from the first reactor into a second reactor, where the second reactor operates at a low temperature, of less than 100° C., the second reactor operating at a higher temperature than the first reactor, to produce the agricultural fiber pulp, wherein the agricultural fibers are processed in a second caustic concentration that is higher than the first caustic concentration of the first reactor.   
     
     
         17 . The method of  claim 16 , wherein the first reactor operates at a temperature in a range of 40° C. to 80° C., and the second reactor operates at a temperature in a range of 85° C. to 99° C. 
     
     
         18 . The method of  claim 17 , wherein the first reactor operates at a ratio of caustic to air dried corn stover or other agricultural feedstock that is from 4% to 12%, or from 5% to 12%. 
     
     
         19 . The method of  claim 16 , wherein chemically pulping the agricultural fibers in the alkaline chemical pulping process is achieved using a liquor that consists of water and caustic.