Mixed lignocellulosic biomass for continuous bioethanol production: logistics, process integration and biodesign

Abstract

The increasing demand for renewable energy and the urgent need to mitigate climate change have driven global interest in bioethanol as a sustainable alternative to fossil fuels. However, reliance on edible feedstocks such as corn, sugarcane or wheat has proven unsustainable due to food-fuel competition. In contrast, second-generation bioethanol production that utilizes lignocellulosic biomass primarily depends on a single biomass, limiting the continuous production because of seasonal variability and high production costs. Mixed lignocellulosic biomass (MLB) utilization has emerged as a promising strategy to address these challenges by integrating diverse agricultural residues, forestry waste, energy crops and industrial by-products within biorefineries. MLB provides supply stability, enhances enzymatic saccharification and minimizes inhibitor formation through synergistic buffering and compositional complementarity. This review comprehensively evaluates the significance of feedstock diversity, pretreatment strategies, enzymatic hydrolysis and fermentation approaches in MLB-based bioethanol production. It further examines process integration strategies, such as simultaneous saccharification and fermentation, consolidated bioprocessing and hybrid reactor systems for year-round operations. Techno-economic assessments demonstrate that MLB reduces the production costs, while life-cycle analyses confirm significant greenhouse gas mitigation potential. Despite these advantages, this study describes challenges in feedstock logistics, inhibitor management, strain robustness and process stability. Moreover, it outlines future directions that emphasize the roles of artificial intelligence and machine learning in feedstock blending, synthetic biology for robust microbial consortia and supportive policy frameworks to promote biomass aggregation. Overall, MLB represents a scalable and sustainable pathway for continuous second-generation bioethanol production, offering environmental, economic and technological advantages over single-feed approaches.