Processing Attributes and Performance of Sweet Sorghum Biomass for Large-Scale Biorefineries: A 1-Year Comparison of Commercial Hybrids and a Cultivar

Processing attributes of sweet sorghum biomass are critical for the manufacture of biofuels and bioproducts. Two commercial sweet sorghum hybrids 105 and 106, late and early maturing, respectively, were compared to inbred, later-maturing Top 76-6 cultivar, for processing attributes at the soft dough (SD) and hard dough (HD) maturity stages. Crops were grown in South Louisiana, and juice extracted from topped whole-stalks was pilot plant clarified and vacuum evaporated to syrups. Hybrid 106 contained a marked amount of auxiliary seed-head/stalk (side-branch tillers), which reduced growth of the main stalk and detrimentally affected juice sugar content and turbidity, as well as clarification and evaporation performance. Except for 105 at the HD stage, turbidity removal across clarification was very acceptable (>92%) and directly related to the median size of the starch granules in the initial raw juice. Clarification was generally better at SD than HD stage. Considerable variation (P < 0.05) existed for total starch in raw juice with 106 >>> Top 76-6 > 105; insoluble and soluble starch were both removed in the clarification mud. Overall, the hybrids processed similarly to cultivar Top 76-6, and 105 had the additional advantages of having low starch and no auxiliary seed-head/stalk. Further studies are now warranted to ascertain environmental effects on processing.