NOVELTY - Treating (m1) a lignocellulosic material involves: performing a steam explosion reaction on lignocellulosic material to form a slurry; adding an alkali material to the slurry in a first conveyor; transferring the slurry from first conveyor to second conveyor; and adding an enzyme solution to the slurry while in, entering or at discharge of the second conveyor, followed by transferring it to a mixer for mixing the slurry, transferring the slurry to a first reactor vessel, and subjecting to enzymatic hydrolysis, where viscosity of the slurry is reduced in first reactor vessel.    USE - For treating a lignocellulosic material (claimed) which are enzymatically hydrolyzed to produce monomeric sugars.    ADVANTAGE - The present method involve the addition of enzymes, optionally in a solution, to a viscous slurry to quickly reduce the viscosity of the slurry. The reduction in viscosity results in the slurry having characteristics more similar to a liquid than to a solid or thick mud like consistency, e.g. the addition of enzymes to a lignocellulosic material causes an enzymatic hydrolysis reaction which reduces the viscosity of the material to the consistency akin to a liquid and yields monomeric sugar(s). The method is also applied to decrease the viscosity of viscous, cellulose-containing material to facilitate transport of the material for other processes.    DETAILED DESCRIPTION - Treating (m1) a lignocellulosic material involves: performing a steam explosion reaction on the lignocellulosic material to produce a slurry including the lignocellulosic material; adding an alkali material to the slurry in a first conveyor, where the alkali material increases the average pH of the slurry moving through the first conveyor; transferring the slurry with the alkali material from the first conveyor to a second conveyor; adding an enzyme solution to the slurry while in, entering or at the discharge of the second conveyor; transferring the slurry with the enzyme solution from the second conveyor slurry to a mixer; mixing the slurry in the mixer, where a second portion of the enzyme solution is added to the slurry during the mixing, and transferring the slurry with the enzyme solution from the mixer to a first reactor vessel; and subjecting the slurry in the first reactor vessel to enzymatic hydrolysis, where the viscosity of the slurry is reduced in the first reactor vessel. INDEPENDENT CLAIMS are included for the following:    (1) liquefaction (m2) involving: performing a steam explosion reaction on a lignocellulosic material to produce a slurry comprising the lignocellulosic material after the steam explosion reaction; mixing the slurry with an alkali-based material in a first screw conveyor until an average pH of the slurry is 4.5-6.5, an average temperature of the slurry is 45-55 degrees C, and the slurry has a consistency of 10-35 wt.% where the wt.% is of insoluble particles as compared to total weight of the slurry; transferring the slurry to a second screw conveyor having an enzyme injection apparatus; discharging from the enzyme injection apparatus a first portion of an enzyme solution to the slurry in the second screw conveyer, where the enzyme is added to the second conveyer from more than one location inside the second conveyor; transferring the slurry to a mixer via a positive displacement pump; mixing the slurry in the mixer at a speed of 400-4000 rpm, for a period of 0.05-200 seconds, where a second portion of the enzyme solution is added to the slurry during the mixing; transferring the slurry to a first reactor to transition the material from a higher viscosity to a lower viscosity to create a liquid material, where the first reactor includes an inverted frustoconical portion having a rotating mixer with arms extending radially from a vertically oriented axial shaft and the arms become successively longer as the diameter of the frustoconical portion expands, and transferring the liquid material to a second reactor for further liquefaction and enzymatic hydrolysis, where the temperature of the slurry is kept at 45-55 degrees C from just prior to the addition of the first portion of the enzyme solution and throughout the duration of the process; and    (2) a system (s1) to liquefy a lignocellulosic material comprising: a steam explosion reactor receiving the lignocellulosic material saturated with water, subjecting the material to a rapid pressure release to cause a steam explosion reaction and discharging a slurry comprising the lignocellulosic material after the steam explosion reaction; a first screw conveyor in fluid communication with a discharge of the steam explosion reactor, and including a rotating screw through which passes the slurry discharged from the steam explosion reactor, and an inlet through which an alkali-based material is injected into the slurry passing through the first screw conveyor; a second screw conveyor in fluid communication with a discharge of the slurry from the first screw conveyor, and including a rotating screw through which passes the slurry from the first screw conveyor and several of inlets for an enzyme to be injected into the slurry in the second screw conveyer; a mixer in fluid communication with a discharge of the second screw conveyor, and including a mixing device rotating at a speed of 400-4000 rpm, where the mixer retains the slurry from the second screw conveyor for 0.05-200 seconds, and the mixing includes an inlet through which the enzyme solution is added to the slurry during mixing; a first reactor to transition the material from a higher viscosity to a lower viscosity to create a liquid material, where the first reactor includes inverted conical upper section having a mixing device with rotating radial arms which are progressively longer in a downward direction through the upper section.