# Steam Explosion-Based Method for the Extraction of Cellulose and Lignin from Rice Straw Waste
###### Abstract
Conventional methods for cellulose and lignin extraction are predominantly alkaline pulping, which uses sodium hydroxide for effective lignin removal [15; 16; 17; 18]; organosolv pulping, utilising organic solvents for efficient delignification [19; 20; 21]; bleaching, involving chemical treatments to purify cellulose [16; 22; 23]; enzymatic treatment, employing enzymes such as cellulase for hydrolysis [24; 25]; TEMPO-mediated oxidation, which oxidises hydroxyl groups to enhance mechanical fibrillation [15; 26]; and ionic liquid pretreatment, using ionic liquids for cellulose dissolution [27; 28]; among others. Each method's unique conditions contribute to its efficacy. However, these methods often face challenges regarding their energy intensity and environmental impact and typically involve the use of harsh chemicals, elevated temperatures, and a high energy consumption, leading to issues such as environmental pollution and safety concerns [29; 30; 31]. These processes also generate large amounts of residues and require expensive and resistant processing equipment as well as considerable waste treatments, thus increasing their environmental footprint. This has driven the scientific community to seek more sustainable and eco-friendly alternatives for cellulose and lignin extraction, such as steam explosion, ultrasound-assisted pretreatment, supercritical fluid pretreatment, and others, in addition to combining both green and conventional methods in order to reduce the impact and optimise the process [31; 32; 33; 34; 35; 36]. Furthermore, the extraction of cellulose and lignin from biomass such as rice straw is fraught with challenges, including effectively removing silica and developing a practical method to isolate its key components [37]. The steam explosion technique emerged as a promising alternative, leveraging thermal and mechanical forces to break down the complex structure of rice straw. This method involves treating the biomass with high-pressure steam and then rapidly reducing the pressure, causing an explosive decompression that disrupts the lignocellulosic matrix [34; 38]. This hydrothermal method also delignifies the residue and explodes the cellulosic fibrils, maintaining the fibre integrity below 240 \({}^{\circ}\)C and yielding separate solutions of lignin, hemicellulose, and cellulose fibres [39]. This approach aligns with green chemistry, enhancing cellulose and lignin accessibility, improving their purity and yield, and reducing the chemical usage and energy requirements [31]. In this sense, the steam explosion technique is not only promising but has already demonstrated its efficacy in various studies. For instance, [PERSON] et al. [9] reported the extraction of cellulose, reaching up to 64.80% of cellule with a high purity. Similarly, [PERSON] et al. [40] achieved an efficient separation of lignin and cellulose, with a lignin extraction yield of 90% and a cellulose yield of 93.2%. These advances represent a milestone in obtaining high-quality materials from biomass. Furthermore, there has been an increasing trend towards integrating conventional methods and green chemistry approaches in the extraction of cellulose and lignin from natural sources. A notable example of this synergy is demonstrated in the work of [PERSON] et al. [41], who utilised a combined process of acid pretreatment, followed by steam explosion and enzymatic hydrolysis for the valorisation of olive byproducts into sugars. Their research highlighted the most effective condition for steam explosion to be at 195 \({}^{\circ}\)C for a duration of 5 min, thereby emphasising the method's effectiveness in delignifying biomass. This hybrid approach not only maximises the purity and yield but also alignswith the principles of sustainability and energy efficiency, demonstrating the potential of combining traditional and modern techniques in biomass biorefinery.