Characterization of Spent Grain from Irish Whiskey Distilleries for Biorefinery Feedstock Potential to Produce High-Value Chemicals and Biopolymers

Distiller’s spent grain (DSG) is a byproduct generated in large quantities during the mashing process, particularly in the production of alcoholic beverages such as whiskey. This study aimed to characterize DSG from nine different distilleries as a potential biorefinery feedstock for the synthesis of high-value bioproducts. Key components, including protein (12.38–26.32%), cellulose (11.75–32.75%), hemicellulose (6.97–19.47%), lignin (8.44–15.71%), and total phenolics (1.42 to 3.97 mg GAE/g), were analyzed to evaluate their variability and suitability for industrial applications. The results reveal that DSG composition varies significantly across distilleries due to differences in processing techniques, even though the starting grain composition had minimal influence. Statistical analysis highlighted the variability of water- and ethanol-soluble extractives (17.34–31.77%) and their potential impact on product consistency. This compositional variability highlights the importance of understanding DSG’s structural properties to optimize its use as a lignocellulosic biomass feedstock. This study emphasizes the potential for utilizing DSG in the production of nanocellulose, bioplastics, phenolic resins, and other sustainable materials, thereby contributing to the circular economy. By linking compositional insights to specific applications, this work establishes a foundation for tailored utilization of DSG in biopolymer production and chemical synthesis. These findings provide valuable insights for biorefinery operations, addressing both sustainability challenges and the economic potential of industrial byproducts.