Deciphering the Impact of Lignin on Anaerobic Digestion: Focus on Inhibition Mechanisms and Methods for Alleviating Inhibition.

China has abundant lignocellulosic biomass resources. These resources are converted into biogas by anaerobic digestion (AD), which not only realizes the comprehensive utilization of waste resources but also obtains abundant biomass energy. However, the low biodegradability of lignocellulosic biomass caused by the complex structure has seriously hindered its utilization by enzymes and microorganisms, resulting in low biogas production and limited development of biogas engineering. The purpose of this work is to analyze the mechanism of lignin inhibiting AD and summarize the main methods for alleviating inhibition. Based on this, this review examines the factors influencing lignin's inhibition of methane production during AD from two key perspectives: (1) discussing lignin's biodegradability challenges, with a focus on its structure, functional groups, and the impact of lignin content in lignocellulosic biomass on its methanogenic potential, and (2) analyzing lignin's impact on each stage of AD. In addition, we provide insights into future research directions in this field.