TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The second solvent extracts into the liquid phase at least 50 (preferably at least 75)% of the lignin present in the lignocellulosic biomass. The first solvent is at least one chemicals selected from hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, polyphosphoric acid, acetic acid, sulfur dioxide, zinc chloride, sodium hydroxide, potassium hydroxide, ammonia, lithium chloride/N,N-dimethylacetamide, 1-butyl-3-methylimidazolium hexafluorophosphate, dimethylsulfoxide/tetrabutylammonium fluoride trihydrate, N-methylmorpholine-N-oxide, cadmium monoxide/ethylenediamine (cadoxen), or water (preferably polyphosphoric acid). The second solvent is at least one chemicals selected from methanol, ethanol, 1-propanol, 2-propanol, acetone, propanal, 1-butanol, 2-butanol, butanal, butanone (methyl ethyl ketone), tert-butanol, or water (preferably acetone and water), where at least two chemicals are added in the step (b1) in a sequential manner. The fourth solvent is at least one materials selected from liquid water, steam, recycle water, process condensate, fermentation-broth condensate, or carbon dioxide. In the solvent combination (c2), the first solvent is polyphosphoric acid and sulfur dioxide, and the second solvent is acetone. In the solvent combination, the first solvent is at least two chemicals selected from (s1), where one of the chemical is selected for the first solvent is sulfur dioxide. Preferred System: The system additionally comprises a device for recovering the first and/or second solvent; and a device for recovering hemicellulose sugars, acetic acid, or lignin.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: During the step (a1), the first solvent dissolves at least 50% (preferably at least 90%, and especially substantially all) of the cellulose or hemicellulose present in the lignocellulosic biomass. During the step (a1), the first solvent dissolves at least 90% of the hemicellulose and cellulose present in the lignocellulosic biomass. During the step (b1), the second solvent precipitates at least 50% (preferably at least 90%, and especially substantially all) of the dissolved cellulose or hemicellulose. During the step (b1), the second solvent precipitates at least 90% of the dissolved cellulose and hemicellulose; and extracts into the liquid phase at least 75% of the lignin present in the lignocellulosic biomass. The method (m1) additionally involves converting the cellulose that precipitates out of the liquid phase in the step (b1) into glucose monomers and/or oligomers, where converting the cellulose to glucose involves enzymatic reactions and acid hydrolysis; recovering and recycling at least one of the solvents back to the steps (a1) and/or (b1). The steps (a1) and (b1) are conducted at 20-80degrees C, and at pressure of 0.1 to 2 bar. The residence time of the steps (a1) and (b1) are each from 5 minutes to 4 hours. One or both of the steps (a1) and (b1) are conducted continuously, semi-continuously, or pseudo-continuously; or in batches. The solvent/solid ratio for the step (a1) is less than 5 (preferably less than 3, and especially less than 2). The method (m1) additionally involves (c1) combining a third solvent with the material of the step (b1) and then separating the substantially solid phase and black liquor, and (d1) combining a fourth solvent with the substantially solid phase from the step (c1) and then separating the solid phase and light liquor; and additionally involves subjecting the black liquor obtained in the step (c1), to (e1) a vapor/liquid separation operation selected from distillation, single-stage evaporation (flash), multiple-effect evaporation, thermocompression, or venturi scrubbing, where the step (e1) involves distillation, and acetic acid is recovered. Where the subjecting step additionally involves recovering at least one solvent selected from the first, second, third, or fourth solvent, and additionally involves recycling at least one of the recovered solvents to at least one of the steps (a1)-(d1), where at least one of the recovered solvents is polyphosphoric acid and acetone; and (f1) a solid/liquid separation operation selected from a centrifuge, filtration device, electrostatic separator, adsorption column, or absorption column (preferably centrifuge), where lignin is recovered. The method (m1) additionally involves subjecting the light liquor, obtained in step the (d1), to (g1) a vapor/liquid separation operation selected from distillation, single-stage evaporation (flash), multiple-effect evaporation, thermocompression, or venturi scrubbing (preferably flash tank), where hemicellulose sugars are recovered. Where the subjecting step involves recovering at least one solvent used in a different step, and additionally involves recycling at least one of the recovered solvents to at least one of the steps (b1)-(d1), where at least one of the recovered solvents is acetone; and additionally involves (h1) a solid/liquid separation operation selected from a centrifuge, a filtration device, an electrostatic separator, an adsorption column, or an absorption column (preferably a centrifuge), and recovering the first solvent and additionally recycling the first solvent to the step (a1). The method (m1) additionally involves fermenting some of the glucose or amorphous cellulose directly, where one of the fermentation products is ethanol or acetone. The lignocellulosic biomass is provided by at least one feedstock modifications selected from reduction of particle size, washing, modifying the moisture content, and conditioning. Alternatively the method (m1) involves process (a): (ia) combining polyphosphoric acid with lignocellulosic biomass, where the polyphosphoric acid dissolves at least 90% of the cellulose present in the lignocellulosic biomass; combining acetone with the resultant material, where at least 90% of the cellulose that is dissolved by the polyphosphoric acid, precipitates out of the liquid phase; combining acetone with the resultant material, and then separating the substantially solid phase and black liquor; and combining water with the substantially solid phase, and then separating the solid phase and light liquor. The process (a) additionally involves separating the black liquor and recovering polyphosphoric acid, where recovering polyphosphoric acid involves burning a process stream and recycling P2O5 and steam back to the step (ia); and recovering acetone from the black and/or light liquor, where the yield of glucose is at least 80 (preferably at least 90, especially at least 95)%, hemicellulose sugars is at least 70 (preferably at least 80, especially at least 85)%, lignin is at least 50 (preferably at least 75)%, acetic acid is at least 80 (preferably at least 90)%. In the process (a), where concurrently the yield of glucose is at least 90 (preferably at least 95)%; hemicellulose sugars is at least 80 (preferably at least 90)%; lignin is at least 50 (preferably at least 75)%; and acetic acid is at least 80 (preferably at least 90)%. Preferred Components: The cellulose that precipitates has reduced crystallinity compared to the initially provided cellulose. The cellulose that precipitates is at least 90% amorphous. EXAMPLE - Corn stover (50 wt.% moisture) was fed into a pretreatment reactor along with recycled polyphosphoric acid, which was present in the reactor at 86 wt.% H3PO4. The ratio of solvent to solids in the reactor was 5. The mixture was allowed to react at 50degrees C for approximately 30 minutes under atmospheric pressure. No heat input was needed during this step because mixing of concentrated acid with water was a weakly exothermic reaction. The polyphosphoric acid not only breaks linkages among lignin, hemicellulose, and cellulose, but also dissolved elementary cellulose fibrils and hemicellulose. A small amount of hydrolysis of large polysaccharides into small fragments occurred. In the precipitation tank, acetone was added to precipitate dissolved cellulose and hemicellulose into insoluble amorphous forms, and to extract solvent-soluble lignin. The solvent/solids ratio in the precipitation tank was 10. The temperature and pressure in the precipitation tank were approximately ambient, and the residence time was one hour. In the unit operation washer 1, more acetone was fed to remove more than 99% of the polyphosphoric acid present as well as the solvent-soluble lignin from the solids. The liquid phase exiting washer 1 was black liquor and contained of polyphosphoric acid, acetone, acetic acid, and dissolved lignin. The temperature and pressure in washer 1 were approximately ambient, and the residence time was 30 minutes. In washer 2, water was fed to wash residual acetone, residual polyphosphoric acid, and water-soluble (low-molecular-weight) hemicellulose oligosaccharides from the solid amorphous cellulose. The liquid stream exiting in washer 2 was light liquor and contained water, acetone, soluble hemicellulose sugars, and a trace amount of polyphosphoric acid. The solid phase comprised of primarily regenerated amorphous cellulose. The temperature and pressure in washer 2 were approximately ambient, and the residence time was 30 minutes. In the distiller, the black liquor containing polyphosphoric acid, acetone, solvent-soluble lignin, and acetic acid was separated along with regeneration of polyphosphoric acid and lignin centrifugation. Acetone and acetic acid were separated easily after distillation and then condensation. With the removal of acetone, the dissolved lignin was precipitated because it had poor solubility in acidic water. The precipitated lignin was separated by centrifugation and drying. In the bottom of the distiller, concentrated polyphosphoric acid containing small amounts of sugars and extractives from the corn stover was regenerated by feeding the bottoms to a furnace. The bottoms were completely burned to produce a mixture containing P2O5, which was recycled to the rector where it forms concentrated polyphosphoric acid. The overall process recovery of polyphosphoric acid was high, such that little or no fresh polyphosphoric acid needs to be added to the reactor. In the flash tank, the light liquor containing acetone, water, some polyphosphoric acid, and soluble hemicellulose sugars was separated by flashing and centrifugation followed by regeneration. A small amount of CaCO3 was added to neutralize the weakly acidic liquid and generate a precipitate, Ca3(PO4)2. CaCO3 was added so that at 99% of the phosphate ion was present in the solid phase. Ca3(PO4)2 was separated, and then regenerated to concentrated polyphosphoric acid by adding concentrated sulfuric acid. Acetone was recycled to a holding tank by flashing and then condensing the vapors. The liquid phase from the bottom of the flash tank was pH-neutral and contains water-soluble hemicellulose sugars. Scanning electron microscopy showed that no fibrillar cellulose remained in the amorphous-cellulose product. The amorphous cellulose was further fed to the hydrolysis tank along with cellulose enzymes. The product from the hydrolysis tank was a solution of glucose, which was fed to the fermenter where ethanol was produced. All of the amorphous cellulose was sent to the hydrolysis tank. The reactivity of the amorphous cellulose was nearly 97% cellulose digestibility that was obtained in a standard digestibility assay (24-hour saccharification time using a Trichoderma enzyme loading of 15 FPU/g glucan at 50degrees C and 10 g glucan per liter solution).