A comprehensive review on lignin obtained from agro-residues: potential source of useful chemicals

Lignin is an aromatic complex polymer that constitutes a major part of biomass, along with cellulose and hemicellulose. Due to its abundant and renewable nature, it can be an ideal candidate for reducing the dependence on fossil resources. However, extraction and further valorization of lignin to useful chemicals has been an uphill task due to its highly branched and recalcitrant nature. Lignin-based biorefineries can be a major boost to a highly populated country like India where there is an ever-rising demand for chemicals. India being an agricultural country produces an exorbitant amount of lignin in the form of agro-residues, which can be properly valorized to achieve the aim of lignin-based biorefineries. In this review, various processes of lignin extraction from biomass residues are discussed in brief, and a major part of the review focuses on recent techniques developed to valorize this aromatic polymer into useful chemicals. These techniques have been compared based on the type of catalyst used, the extent of depolymerization, and the monomeric yield and selectivity of the process. Finally, the potential of lignin as a sustainable source of useful chemicals in India is discussed.

Automated summary

Lignin is a major aromatic polymer that can be an ideal choice for reducing dependence on fossil resources. India, as an agricultural country, can utilize a large amount of agricultural residues to produce lignin and support lignin-based biorefineries. This review discusses various techniques for lignin extraction and utilization, and explores the potential of lignin as a sustainable source of useful chemicals in India.