The utilization of low-cost and abundant lignocellulosic residues for sustainable production of bioenergy and biofuels (such as biogas) will play a pivotal role in the future decarbonized circular economy energy supply. Among all of the bioconversion technologies for the production of bioenergy and biofuels, anaerobic digestion (AD) has many advantages such as sustainably managing organic wastes, producing renewable biogas, and providing for nutrient recycling with low energy input, all of which are important in contributing to a low-carbon emission circular economy. However, the inherent rigid polymeric structure of lignocellulose makes the material less accessible to microorganisms during the degradation process in AD, resulting in relatively low feedstock conversion efficiency and subsequent sub-optimal biogas production. Pretreatment may be required to alter the lignocellulosic structure to improve the conversion process and biogas production. This chapter presents recently developed pretreatment methods (including physical, chemical, biological) for enhancement of the digestion performance and biogas/biomethane production yield from lignocellulosic residues. Thermochemical bioenergy technologies such as pyrolysis and hydrothermal carbonization may be integrated with AD, contributing to synergistic benefits to future negative emission systems. Future work is required to evaluate the economic feasibility and sustainability of novel pretreatments required for enhanced AD of lignocellulosic residues.