TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The acid of the mixture of step (a1) and (a2) comprises at least one of sulfuric acid, sulfur dioxide, sulfurous acid, hydrochloric acid, oxalic acid and/or hydrogen peroxide. The aqueous first acid comprises aqueous sulfuric acid present in an amount of 1-2.5 wt./wt.% of the solution. The mixture of first step has a consistency of 5-30%. The aqueous second acid comprises aqueous solution of sulfuric acid present in an amount of 2-9 wt./wt.%. The mixture of second step has a consistency of 5-30%.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The step (a1) involves generating a hemicellulose-depleted material and sugars from the hemicellulose, and further includes prior to steps (a2) and (a3), the step of removing the sugars produced from the mixture. The first treatment temperature (T1) is 130-180 degrees C. The second treatment temperature (T2) is 190-210 degrees C. The mechanical size reduction is done by disc refining. The step (a3) includes adjusting the consistency of the material to 5-100% prior to milling. The mechanical size reduction of step (a3) is conducted to produce material having an average length of 0.1-2 mm. The milling of step (a3) involves refining the material to produce fiber bundles having a width of 0.04-0.2 mm. The step (a3) is carried out subsequent to step (a2). The conditions (i), (ii), and (iii) are selected so as to reduce net specific energy consumed in step (a3) by at least 95% when compared to untreated material. The step (a3) includes disc refining the material to a Canadian Standard Freeness (CSF) below about 700 ml determined according to TAPPI T 227, and further involves the step (a4) of enzymatically hydrolyzing the material of step (a3) to form glucose in molar yield of at least 70% based on the cellulose content of the material of step (a1). The method for treating wood chips involves: ia) exposing a first mixture comprising the wood chips and an aqueous sulfuric acid solution (1.0 to 1.5 wt./wt.%), at a temperature of 150 degrees C to 180 degrees C for a period of 15-30 minutes, where the mixture has a consistency of 10-25%, to at least partially hydrolyze hemicellulose of the wood chips; (iia) removing xylose and mannose produced in step (ia) from the mixture; (iiia) exposing a second mixture comprising the wood chips produced in step (ia) and an aqueous sulfuric acid solution (3.0 to 10 wt./wt.%), at a temperature of 180 degrees C to 220 degrees C, where the second mixture has a consistency of 10-25%, to at least partially hydrolyze hemicellulose of the wood chips; and (iva) physically reducing the wood chips produced in step (iiia) by disc refining to produce cellulosic fibers which will undergo hydrolysis to produce glucose at a yield of at least 90% in presence of 15 FPU/g glucan, and where net specific energy consumed in step (iiia) is reduced by at least 95% when compared to disc refining of untreated wood chips of step (ia) under the same conditions of step (iiia). Preferred Components: The cellulose-containing material of step (a1) comprises wood chips having an average length of up to about 50 mm. EXAMPLE - No suitable example given.