Clean sugar and lignin from non-chemically pretreated lignocellulosic biomass

Abstract

Methods of producing clean (e.g., low sulfur and metal ion content, and free of fermentation inhibitors) sugar and lignin-rich streams, and downstream conversion products, from lignocellulosic biomass, may include obtaining non-chemically pretreated, milled lignocellulosic biomass, reacting the milled lignocellulosic biomass with an enzymatic agent to produce a slurry that includes converted monomeric lignocellulosic sugars and lignin-rich residuals, and separating the slurry into a sugar stream that includes the converted monomeric lignocellulosic sugars and a lignin-rich stream that includes the lignin-rich residuals. The sugar stream, not including water, includes at least 75% monomeric lignocellulosic sugar, less than 0.20% sulfur, and less than 3.0% metal ion content, and the lignin-rich stream includes at least 35% lignin and less than 0.50% sulfur. Some methods include producing fermentation products such as alcohols and/or organic acids from the sugar stream, and/or use of the lignin residuals in fuels.

What is claimed is: 
     
         1 . A method of lignocellulosic biomass conversion, the method comprising:
 obtaining non-chemically pretreated, milled lignocellulosic biomass having a particle size less than about 300 microns;   reacting the milled lignocellulosic biomass with an enzymatic agent to produce a slurry that includes converted monomeric lignocellulosic sugars and lignin-rich residuals; and   separating the slurry into a sugar composition that includes the converted monomeric lignocellulosic sugars and a lignin-rich composition that includes the lignin-rich residuals;   wherein the sugar composition, not including water, includes at least 75% monomeric lignocellulosic sugar, less than 0.20% sulfur, and less than 3.0% metal ion content; and   wherein the lignin-rich composition includes at least 35% lignin and less than 0.50% sulfur.   
     
     
         2 . The method of  claim 1 , wherein the lignocellulosic biomass is wood. 
     
     
         3 . The method of  claim 2 , wherein the wood is softwood. 
     
     
         4 . The method of  claim 1 , wherein the slurry is free of furans and other fermentation inhibitors. 
     
     
         5 . The method of  claim 1 , wherein separating the slurry includes filtering the slurry to yield a filtrate that includes the sugar composition, and a high solid stream that includes the lignin-rich composition and undigested lignocellulosic biomass. 
     
     
         6 . The method of  claim 1 , further comprising, subsequent to separating the slurry, concentrating the sugar composition to produce a concentrated lignocellulosic sugar mixture. 
     
     
         7 . The concentrated lignocellulosic sugar mixture produced according to the method of  claim 6 . 
     
     
         8 . The method of any of  claim 1 , further comprising, subsequent to separating the slurry, drying the lignin-rich composition to produce a lignin composition having a solid content of at least 80%. 
     
     
         9 . The lignin composition produced according to the method of  claim 8 . 
     
     
         10 . A fuel incorporating the lignin composition of  claim 9 , wherein the fuel is one or more of a solid fuel and a liquid fuel comprising a suspension of the lignin composition. 
     
     
         11 . The method of  claim 1 , wherein the composition of the sugar composition, not including water, includes at least 85.0% (w/w) monomeric lignocellulosic sugar. 
     
     
         12 . The method of  claim 1 , wherein the composition of the sugar composition, not including water, includes at least 90.0% (w/w) monomeric lignocellulosic sugar. 
     
     
         13 . The method of  claim 1 , further comprising producing a fermentation product from the converted monomeric lignocellulosic sugars in the sugar composition. 
     
     
         14 . The method of  claim 13 , wherein the fermentation product includes one or more of an alcohol and an organic acid. 
     
     
         15 . A method of hydrolytic lignocellulosic biomass conversion, the method comprising:
 in a first hydrolysis reaction, reacting non-chemically pretreated, milled lignocellulosic biomass to with an enzymatic agent to produce a first slurry that includes converted lignocellulosic sugars, lignin-rich residuals, and unused enzymatic agent;   mixing additional non-chemically pretreated, milled lignocellulosic biomass with the first slurry to produce a slurry mixture;   separating the converted lignocellulosic sugars from the slurry mixture;   in a second hydrolysis reaction, reacting the non-chemically pretreated, milled lignocellulosic biomass in the slurry mixture with the unused enzymatic agent in the slurry mixture to produce a second slurry that includes converted lignocellulosic sugars and lignin-rich residuals; and   separating the converted lignocellulosic sugars from the second slurry.   
     
     
         16 . The method of  claim 15 ,
 wherein the first hydrolysis reaction is carried out in a hydrolysis unit; wherein the separating is carried out in a filtration unit; and   wherein the mixing is carried out while transporting the slurry mixture from the hydrolysis unit to the filtration unit.   
     
     
         17 . The method of  claim 15 , further including one or more of:
 combining the converted lignocellulosic sugars separated from the first and second slurries, and combining the lignin-rich residuals from the first and second slurries.