Pathway Development for Brewer’s Spent Grain Valorization Using Multi-Objective Optimization

Abstract

Brewer’s spent grain (BSG) represents a significant biowaste stream in the European beer industry with limited valorization beyond animal feed, biogas and landfilling. This study presents a multi-objective optimization approach to guide decision-making in the design of a biorefinery utilizing BSG as feedstock, ensuring a balance between economic profitability and sustainability.In addition to traditional valorization options, a comprehensive review of potential products and conversion pathways – including biological, thermochemical and extraction routes – was conducted based on biomass characterization. The proposed configurations were then evaluated both in terms of economic performance using earnings before interest and taxes and minimum selling prices, and the environmental impact was determined using a carbon footprint analysis compliant with ISO 14067.The results obtained suggest that animal feed remains the optimal processing route for maximizing profitability, while compost production has the lowest carbon footprint. Ethanol and hydrochar also stood out for their environmental value and proximity to market competitiveness, based on their minimum selling price. Furthermore, the comparison of suboptimal configurations was complemented by an evaluation of cascade conversion strategies which suggested that only if synergies between different processing stages are achieved, can the combination of multiple valorization routes maximize resource efficiency and ensure the full utilization of BSG.

Keywords: Superstructure Optimization, Early-Stage Biorefinery Design, OUTDOOR, Minimum Selling Price, Carbon Footprint Analysis