How to Reduce Char Formation in the Lignin Degradation Process: A Review

Abstract As the most abundant biomass resource in nature, the utilization of renewable aromatic rings contained in lignin has always been the focal point for materials science and chemistry. Many of the current lignin degradation methods need to be carried out under harsh conditions such as extremely high temperatures or high pressures. This leads to the cross‐linking reaction between lignin and depolymerization intermediates to produce solid char. The milder method also requires the use of heating, which may also lead to the polymerization of some intermediates in the reaction to form char. It has been a difficult problem for researchers to find a way to reduce the solid char. This review discusses different methods to avoid or reduce char formation and sedimentation, including thermal degradation, electrochemical catalysis, fungal degradation, and mechanochemical methods. The aim of the review is to help reduce char formation during lignin degradation and to increase the rate of lignin biomass degradation.