Advancements in ammonia-based pretreatment: key benefits and industry applications

Abstract

The development of sustainable pretreatment technologies is essential for improving biomass conversion efficiency in second generation biorefineries. This review provides a comprehensive analysis of ammonia-based pretreatment methods, tracing their evolution from early advancements to recent innovations. It highlights advanced technologies such as Ammonia Fiber Expansion (AFEX), Extractive Ammonia (EA), and Compacted Biomass with Recycled Ammonia (COBRA), alongside other approaches, including dilute ammonia, gaseous, and aqueous methods. These pretreatment methods vary in their effectiveness, particularly in lignin removal and lignin carbohydrate complex modification, with most ammonia preserving cellulose while their impact on hemicellulose and lignin range from minimal alterations to extensive removal. The review also explores the integration of ammonia-based pretreatment with biomass densification strategies, emphasizing their role in improving feedstock logistics while maintaining conversion efficiency. Recent innovations in sustainable ammonia production such as electrochemical synthesis and biomass-based processes are discussed, showcasing opportunities to develop environmentally friendly pretreatment solutions. Additionally, the applications of ammonia-pretreated biomass are examined across three key sectors: biofuel production, leveraging enzymatic hydrolysis and fermentation; animal feed, with enhanced digestibility and nutritional benefits; and biomaterial development, including lipid and protein extraction for value-added products. This review offers a comprehensive understanding of ammonia-based pretreatment technologies and their expanding potential in sustainable biorefining applications.