Techno‐economic analysis of the valorization of brewers spent grains: production of xylitol and xylo‐oligosaccharides

Abstract

AbstractBACKGROUNDBrewers spent grains (BSG) represents ≤85% of a brewery's solid waste and common disposal to landfill is increasingly more difficult. Yet BSG is a food‐grade by‐product with potential economic valorization that can significantly improve resource efficiency and reduction in carbon emissions. This study investigated valorization of BSG through the application of novel high solids hydrothermal processing technology in a small‐scale biorefinery, annexed to a brewery. It focused on three scenarios for the production of: (A) the sugar replacement xylitol; (B) prebiotic xylo‐oligosaccharide (XOS); and (C) co‐production of xylitol and XOS. Economic assessment was conducted by comparing the capital and operating expenditure from process simulations created in Aspen Plus®. The process models developed were supplemented with experimental data to improve accuracy.RESULTSInternal rate of return (IRR) values obtained were greater than the hurdle rate of 9.7% for all scenarios when considering a conservative market price for xylitol and XOS as US$4500 t–1, yet dedicated production of XOS was economically more favourable with a minimum required selling price (MRSP) of US$2509 t–1 compared to US$4153 t–1 for xylitol. Additionally, the scenario for co‐production of xylitol and XOS achieved the lowest MRSP of US$2182 t–1. By‐products significantly contributed to 32.7%, 14.2% and 27.5% of the revenue generated in scenarios A, B and C, respectively.CONCLUSIONThese results provide a good platform from which to develop the cost‐effective commercial production of XOS and xylitol from BSG. © 2021 Society of Chemical Industry