TECHNOLOGY FOCUS - BIOLOGY - Preferred Method: The method further comprises measuring the viscosity of the phenolics liquid phase. The steps of reducing the viscosity and measuring the viscosity take place at the same time. The alcoholic component is formed by a catalytic reduction reaction of soluble carbohydrates that are derived from the cellulosic biomass solids. The step of reducing the viscosity of the phenolics liquid phase comprises: reacting the phenolics liquid phase with a base; or heating the phenolics liquid phase in the presence of molecular hydrogen and the slurry catalyst. The phenolics liquid phase is heated to a temperature sufficient, preferably to a temperature of at least 270 degrees C, to at least partially depolymerize the lignin in it. The method further comprises forming methanol from the phenolics liquid phase while reducing its viscosity. The step of reducing the viscosity of the phenolics liquid phase takes place in the presence of the cellulosic biomass solids. The method further comprises separating the phenolics liquid phase from the cellulosic biomass solids after reducing its viscosity, where the phenolics liquid phase is separated from the cellulosic biomass solids before reducing its viscosity. The method further comprises separating the phenolics liquid phase from the aqueous phase before or after reducing the viscosity of the phenolics liquid phase. The viscosity of the phenolics liquid phase is reduced by at most 20%. The viscosity is reduced sufficiently for the slurry catalyst accumulated in the phenolics liquid phase to be separated from it. The method further comprises: separating the phenolics liquid phase and the slurry catalyst accumulated in it from the cellulosic biomass solids; and after reducing the viscosity of the phenolics liquid phase, separating the slurry catalyst from it; and returning the slurry catalyst to the cellulosic biomass solids. The method further comprises circulating at least a portion of the aqueous phase through the cellulosic biomass solids. The second temperature is sufficient to at least partially depolymerize the lignin in the phenolics liquid phase. The second temperature is greater than or equal to 270 degrees C. The first temperature is less than or equal to 250 degrees C. Preferred Components: The alcoholic component comprises a monohydric alcohol, a glycol (preferred) and/or a triol.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The biomass conversion system further comprises: a feedback mechanism communicatively coupled to the viscosity measurement device and a temperature control mechanism, where the temperature control mechanism is activated by a viscosity measurement that is above a threshold value; a solids introduction mechanism (4) coupled to the top of the hydrothermal digestion unit; and a second fluid conduit configured to remove a second fluid from the hydrothermal digestion unit. The first fluid conduit is configured to return the first fluid from an upper portion of the hydrothermal digestion unit to a lower portion of the hydrothermal digestion unit. The viscosity measurement device is located within the second fluid conduit or is in flow communication with the second fluid conduit. The second fluid conduit is configured to return the second fluid to the hydrothermal digestion unit. The second fluid conduit is configured to return the second fluid from a lower portion of the hydrothermal digestion unit to an upper portion of the hydrothermal digestion unit. EXAMPLE - A 75 ml reactor was charged with 20.2 g of 25% 2-propanol solvent in deionized water, 0.12 g of sodium carbonate buffer and 0.302 g of sulfided nickel oxide promoted cobalt molybdate catalyst. The reactor was then charged with 4.98 g of southern pine mini-chips (39% moisture), before pressurizing with 52 bar of hydrogen. The stirred reactor was heated to 190 degrees C for 1 hour, followed by heating to 240 degrees C for 4 hours to complete a 5 hours cycle. At the end of the cycle, the reactor was cooled and allowed to gravity settle overnight. Then 4 g of liquid phase was withdrawn as product, and 4 g of wood chips were added to initiate a subsequent reaction cycle. The foregoing sequence was continued for 28 cycles of wood chip addition, after which time the upper aqueous phase (containing glycols and monooxygenated compounds) was decanted from a black, lower phase which also contained the settled catalyst. The lower phase was too viscous to flow at room temperature. One part of the lower phase was dissolved in 10 parts n-octanol and analyzed by gas chromatography.