Nonwoody Lignin for Phenolics Production

Nonwoody lignin derived from grasses, crop wastes, and herbaceous plants has various amounts of G, S, and H units. The availability of nonwoody materials provides a potential source for high-value chemicals such as ferulic acid, guaiacol, vanillin, p-coumaric acid, syringol, syringaldehyde, and more, which are utilize in various fields. This chapter presents the process of producing phenolic compounds from nonwoody lignin, including depolymerization, separation, and purification, as well as its industrial applications. The phenolic production of nonwoody lignin is affected by its monolignol structure and depolymerization conditions (temperature, pressure, and catalyst). Some depolymerization methods have been investigated, including thermal-chemical, oxidative, reductive, chemical-catalytic, and biological degradation methods. These techniques are intended to improve the efficiency and efficacy of depolymerization to optimize the yield of phenolic compounds while avoiding repolymerization, which can reduce yield. Separation and purification are also necessary steps after depolymerization to generate high-value phenolic compounds. Future plans should prioritize the integration of diverse technologies and methodologies to improve nonwoody lignin degradation to the purification stage of industrial chain design, allowing for large-scale production of phenolic substances generated from nonwoody lignin.