TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: In the methods (M1) and (M2), at least 5 wt.% of the cellulosic biomass solids are converted into the glycol. The step (a) comprises adding the polyol organic solvent to the cellulosic biomass solids from an external source. The method (M1) further comprises: at least partially converting the polyol organic solvent into the glycol before converting the cellulosic biomass solids into the reaction product; at least partially drying the reaction product to form a dried glycol, where step of at least partially drying the reaction product comprises a distillation to separate water from the glycol; a step (r1) of transforming at least a portion of the dried glycol into a monohydric alcohol, exposing the monohydric alcohol or a product formed from it to a condensation catalyst and converting the monohydric alcohol to a higher molecular weight compound using the condensation catalyst; separating the dried glycol from the reaction product, exposing the dried glycol or a product formed from it to a condensation catalyst, and converting the dried glycol to a higher molecular weight compound using the condensation catalyst; and a step (u1) of removing at least a portion of the reaction product from the hydrothermal digestion unit and recirculating at least a portion of the reaction product to it, where the reaction product also contains at least a portion of the slurry catalyst. The step (b) is carried out in a hydrothermal digestion unit in the presence of molecular hydrogen and a slurry catalyst capable of activating the molecular hydrogen. The slurry catalyst is: distributed in the cellulosic biomass solids using fluid flow; and circulated through a fluid circulation loop external to the hydrothermal digestion unit. The glycol is at least partially transformed into the monohydric alcohol or the higher molecular weight compound external to the hydrothermal digestion unit. The method (M1) further comprises: (s1) at least partially drying the reaction product external to the hydrothermal digestion unit to form a dried glycol, before at least partially transforming the glycol into the monohydric alcohol or the higher molecular weight compound; and (t1) returning at least a portion of the dried glycol and/or the monohydric alcohol to the hydrothermal digestion unit. The method (M2) further comprises: at least partially converting the glycerol into the glycol before forming soluble carbohydrates; adding the solvent system to the cellulosic biomass solids from an external source; the step (c) as above per se; and the step (s1) as above per se; the step (r1) as above per se; exposing the dried glycol or a product formed from it to a condensation catalyst, and converting the glycol to the higher molecular weight compound using the condensation catalyst; and the step (t1) as above per se; and the step (u1) as above per se. Preferred Components: The polyol organic solvent is derived from a biological source. The polyol organic solvent comprises glycerol. The solvent system further comprises: water; and an additional organic solvent consisting of a glycol and/or a monohydric alcohol. The dried glycol comprises less than or equal to 35 wt.% water. The slurry catalyst is a poison-tolerant catalyst, preferably a sulfided catalyst. EXAMPLE - A 75 ml reactor was charged with 25.05 g of 90 wt.% glycerol in deionized water to provide a solvent mixture. To the solvent mixture, 0.126 g of potassium carbonate buffer was added, along with 0.305 g of the cobalt molybdate catalyst. The reactor was pressurized to 52 bar with hydrogen and heated to 190 degrees C for 1 hour, followed by heating to 230 degrees C for 4 hours. Gas chromatography (GC) analysis revealed the formation of 2.8 wt.% ethylene glycol and 3.9 wt.% 1,2-propylene glycol as the primary products, along with small amounts of other oxygenated intermediates. Subsequent cycles were run following addition of 2.7 g of Southern pine wood minichips (39% moisture), and buffer as needed to maintain the pH at 5-7. Following each cycle, a 1 g sample of product was withdrawn for GC analysis using the same temperature profile and hydrogen addition. Upon opening the reactor for sampling and wood addition, a dark, viscous layer was noted at the top of the reactor. The sequence was continued for 22 cycles, with addition of 56.7 g of wood chips in total. All wood was dissolved, with a final residue of 1.103 g of a viscous phase which could be dissolved in acetone. The glycerol concentration diminished to less than 1 wt.% in the final product, indicating a continued reaction of glycerol during co-processing of the biomass feed.