A Review on Chemical Pretreatment Methods of Lignocellulosic Biomass: Recent Advances and Progress

The lignocellulose based biorefinery process plays a significant role in the production of value-added products to achieve the sustainable development goals that aim for a bio-circular-green economy. Due to the recalcitrant nature of the biomass components, different types of pretreatment methods are essential to make available carbohydrates for saccharification and fermentation. The mechanism, advantages, challenges, innovations, and technologies of various chemical pretreatment processes are summarized in this review. Based on the literature survey, chemicals such as acids, alkalis, organosolv, oxidative agents, ionic liquids, and deep eutectic solvents are covered in the review. Moreover, combined chemical pretreatment strategies are also discussed in this study, which can be utilized in industries. There are many challenges, such as the efficiency of the process, reaction conditions, formation of inhibitors, techno-economic feasibility, and environmental sustainability, which require further investigations to overcome these limitations to choose the best option for the feasible process. This review could be the guideline for the future direction in the improvement of pretreatment methods for the synthesis of value-added products.