Effect of Storage Method and Duration On the Bioprocessing of Lignocellulosic Biomass

Lignocellulosic biorefineries require an efficient system of biomass storage between harvesting and processing. This study reports the effect of storage method and duration on the composition and processing performance of sweet sorghum bagasse. Sorghum bagasse was harvested at 85% moisture content, crushed to extract the juice, and then stored. Four storage conditions were used: frozen after crushing (control), ensiled after crushing (67% moisture content), or dried in the field and baled at high (27% by weight) or low (11% by weight) moisture contents. After 24 weeks of storage indoors at 20°C, 5.5% dry matter was lost from low moisture content bales, 29.4% from high moisture bales, and 7% from silage. Compositional analysis and mass balances determined that mass loss was primarily carbohydrates. Pretreatment and SSF at high solids loading (15% w/w) were then carried out for the materials. Distinct differences in performance were noted, with lower enzymatic digestibility of the glucan observed for dry storage compared to wet storage.

To examine non-compositional impacts of storage method, bagasse samples were enzymatically hydrolyzed at 1% w/w solids loading without drying, air-dried (20°C), and oven-dried (45 °C). Release of glucose stopped after <5 hours for dried bagasse with final yields being 70% (air-dried) and 57% (oven-dried) of total glucan. By comparison, non-dried samples continued to hydrolyze beyond 5 hours, resulting 87% glucan yield after 24 hours. These results indicate that hornification during drying may also negatively affect enzyme accessibility to the cellulose and lower bioprocessing performance.