The technical or economic valuation of a feedstock for bioprocessing is inherently dependent upon detailed knowledge of its chemical composition. Although a substantial effort has been extended towards elucidating feedstock composition, water- and/or ethanol-soluble materials are typically only quantified gravimetrically and identified as ‘extractives’. Our group has previously reported the first compositional analyses of water-soluble materials in representative corn stover and switchgrass feedstocks. One finding of particular interest was that water-soluble, fermentable sugars (primarily glucose, fructose, and sucrose) represented up to 17% and 13% of the dry weight of corn stover and switchgrass feedstocks, respectively. These results suggest that a feedstock’s ethanol yield could potentially be improved via independent fermentation of water-soluble sugars found in the ‘extractives’ fraction. Assuming that all water-soluble sugars were converted to ethanol, product yields for corn stover and switchgrass could be improved by 12 and 6 gal/ton, respectively.  More recently, we have assessed the composition of water-soluble materials in seven sorghum variants. These analyses indicate that fermentable sugars represent up to 74% of the dry weight of extractives (29% of the dry weight of the feedstock) in sorghum.  In contrast to the moderate increases in ethanol yield that may be obtained for corn stover and switchgrass, independent fermentation of water-soluble sugars found in these sorghum variants could provide an additional 87 gallons of ethanol per ton of feedstock. This poster will detail these comparisons, as well as provide compositional data resulting in approximate 80% mass closure for extractives in the seven investigated sorghum variants.