Lignocellulosic substrate is a resource that contains a locked energy reserve that is normally lost during anaerobic digestion. Lignocellulosic substrate is one of the most abundant sources of organic matter available and yet its energy recovery has much room for improvement. Lignocellulosic substrate has cellular properties that are deemed extremely difficult to degrade due to complexity which is why this energy reserve is never unlocked during anaerobic digestion. There are several successful pretreatment methods that are used to degrade this lignocellulosic substrate and unlock this energy reserve. This paper will focus on the methods that include mechanical, irradiation, chemical and combined pretreatment processes. Analysis is conducted on all the studies that are obtained to compare the successes of the different types of pretreatment processes used. Each of the different listed pretreatment processes have different energy requirements, treatment times, and solvent requirement and are acting to enhancing methane production. The improvement in methane production varies from process to process and study to study creating a need to compile all of this valuable data into this research report. This will help future researchers in navigating the available studies of pretreatment of lignocellulosic substrate for improving methane production.