Valorization of Rice Straw for Ethanol Production and Lignin Recovery Through Acidic and Alkaline Pre-treatments

Rice straw is a valuable resource that is rich in beneficial natural substances such as cellulose, hemicellulose, and lignin. These substances are commonly used in the production of biofuels and other value-added products. However, there is still a challenge in applying the biorefinery residue lignin on a large scale. The raw solid products recovered from rice straw usually contain various contaminants and heterogeneous lignin with complex molecular weight distribution. Currently, the most surplus rice straw is inefficiently burned in the field, leading to acute respiratory illnesses and dangerously high pollution levels. This is because of its limited use and low nutritional value as fodder. Therefore, new methods must be developed to use it as a feedstock for producing biofuels and biopower. Recent studies have evaluated changes in the chemical composition, physio-chemical structure, lignin-carbohydrate connections, and accessibility after several pretreatment methods, mainly acid or alkali or combined, to reduce the recalcitrance of rice straw. Utilizing every component of rice straw in a biorefinery-based method makes the process environmentally friendly and sustainable.