Microwave irradiation pretreatment is more conventional alternative technique to the simple heating process as it simply alters theultra-structure of cellulose & degrades or partially removes hemicelluloses and lignin. It also enhances the enzymatic sensitivity of reducing sugars by disruption of silicified waxy surface. According toGabhane et al. [105], microwave irradiation aids in cellulosic disintegration mainly due to dielectric polarization through molecular collision. The main advantages of this method are: high uniformity andselectivity short process time and less energy requirement compared tothe traditional heating.Jackowiak et al. [106] irradiated wheat straw (WS) with MW at150 °C and found that it was able to increase methane yield by 28% forWS as compared with untreated WS. Li et al. [107] investigated thatMW pretreatment at 260 °C had an adverse effect on methane yield andmethane production rate of an energy grass, Pennisetum hybrid. It wasobserved that 175 °C, biogas production decreased due to formation ofrefractory compounds. MW pretreatment might have the side effect ofproducing heat induced inhibitory products like phenolic compoundsand furfural. Hence MW irradiation of lignocellulosic biomass is notfruitful individually due to formation of these inhibitors but usually hasbeen used for providing heat assistance for acid and alkaline pretreatment and also for pretreating micro-organisms (inoculum) to supresstheir methanogenic activity [43]. Montingelli et al. [81] applied MWpretreatment on macroalgal biomass with beating and ball milling andreported its negative impact on bioenergy production with ball milling.