Recovery of inorganic salt during processing of lignocellulosic feedstocks

A method for producing and recovering an inorganic salt slurry comprising one or more inorganic salts comprising ammonium sulfate salts, potassium sulfate salts, ammonium phosphate salts, potassium phosphate salts or mixtures thereof, and for producing alcohol from a lignocellulosic feedstock, said method comprising:

• a) pretreating the lignocellulosic feedstock by adding one or more than one acid selected from the group consisting of sulfuric acid, and phosphoric acid to the lignocellulosic feedstock to produce a pretreated lignocellulosic feedstock product comprising xylose and cellulose;
• b) adding one or more than one soluble base selected from the group consisting of ammonium hydroxide, ammonia and potassium hydroxide to the pretreated lignocellulosic feedstock product, which pretreated lignocellulosic feedstock product has a pH of between about 0.4 and about 2.0, to adjust the pretreated lignocellulosic feedstock product to a pH of about 4.0 to about 6.0 to produce a neutralized feedstock product containing xylose, cellulose and one or more soluble inorganic salts and cellulose, wherein said inorganic salt salts comprise ammonium sulfate salts, potassium sulfate salts, ammonium phosphate salts, potassium phosphate salts or mixtures thereof;
• c) substantially separating the neutralized feedstock product into a xylose-inorganic & salts product and a cellulose product;
• d) enzymatically hydrolyzing the cellulose product with cellulase enzymes to produce glucose;
• e) producing an alcohol product by fermenting the glucose with one or more microbes;
• f) obtaining a product comprising xylose and a separate inorganic salts product comprising one or more of the inorganic salts from the xylose-inorganic salts product of step c;
• g) recovering the inorganic salt slurry from the inorganic salts product of step f;
• and concentrating the inorganic product.

A method for producing and recovering an inorganic salt slurry comprising one or more inorganic salts comprising ammonium sulfate salts, potassium sulfate salts, ammonium phosphate salts, potassium phosphate salts or mixtures thereof, and for producing a concentrated ethanol product from a lignocellulosic feedstock, said method comprising:

• a) pretreating the lignocellulosic feedstock by adding one or more than one acid selected from the group of sulfuric acid and phosphoric acid to the lignocellulosic feedstock to produce a pretreated lignocellulosic feedstock product comprising xylose and cellulose;
• b) adding one or more than one soluble base selected from the group consisting of ammonium hydroxide, ammonia and potassium hydroxide to the pretreated lignocellulosic feedstock product, which pretreated lignocellulosic feedstock product has a pH of about 0.4 to about 2.0, to adjust the pretreated lignocellulosic feedstock to a pH of about 4.0 to about 6.0 to produce a neutralized feedstock product containing xylose, cellulose and one or more soluble inorganic salts, wherein said inorganic salts comprise ammonium sulfate salts, potassium sulfate salts, ammonium phosphate salts, potassium phosphate salts or mixtures thereof;
• c) enzymatically hydrolysing the neutralized feedstock product with cellulase enzymes to produce a sugar stream and an unhydrolyzed residue;
• d) fermenting the sugar stream to produce a fermentation broth comprising ethanol;
• e) distilling the fermentation broth to produce concentrated ethanol and still bottoms;
• f) obtaining a separate inorganic salts product comprising one or more of the inorganic salts from the still bottoms of step e;
• and
• g) recovering the inorganic salt slurry from the inorganic salts product of step f, and concentrating the inorganic salts product.