Sequential multiple compound extraction from biomass using steam explosion as pretreatment: A review

Pretreating biomass efficiently in an environmentally friendly way is crucial for unlocking its valuable components. Among various pretreatment techniques, steam explosion (SE) has shown promising results, characterized by high efficiency, low operating energy, and reduced environmental impact. Pretreating biomass with steam SE is attractive due to its high efficiency, low operating energy, and reduced environmental impact. Nevertheless, temperature, severity factor (SF), and sample presoaking affect an SE pretreatment performance. Higher temperatures improve hydrolysis rates but produce unwanted by-products. Conversely, lower temperatures increase the amount of recalcitrant chemicals in the feedstock. Meanwhile, the SF measures the pretreatment harshness of the temperature and residence time. Higher SF results in more significant biomass fragmentation. In addition, water presoaking is critical in SE pretreatments as it allows feedstock to soak up more steam. The central aim of this review is to explore the potential of SE for the sequential recovery of multiple lignocellulosic components from biomass. This aspect has not been extensively reported in the literature. Moreover, the review assesses the subsequent processes involved in obtaining derivatives from these extracted components and optimizing SE parameters. Overall, the influence of these parameters on the extraction is complex and depends on the specific pretreatment utilized. Generally, based on reported SF required for each component, the extraction of various compounds with multiple SE pretreatments from a biomass sample is feasible in the sequence of: flavonoids and hydrocolloids are extracted first, followed by oils, then cellulose (fiber), hemicellulose and cellulose (for fermentation), and finally lignin. Future studies should focus on improving SE parameters to maximize the sequential recovery of multiple biomass components. Further exploration of this process could yield valuable biomass optimization and utilization advancements.