Different methods of pretreatment including alkali treatment, treatment with ultrasound, biological treatment using laccase enzyme and combined treatment like ultrasound-laccase for Napier grass have been tried. With alkali pretreatment optimized conditions obtained were sodium hydroxide 0.3% w/v giving 86% delignification at temperature of 80 degrees C, treatment time of 2 h. In physical methods of treatment ultrasound, at a temperature of 45 degrees C, treatment time of 2 h, operating at frequency 24 kHz and power of 100 W gave 18% delignification. For laccase pretreatment, optimized conditions obtained were 300 rpm impeller speed, enzyme concentration 10 U/gm of Napier grass gave 50% delignification with cellulose. The optimized conditions for delignification by using combination treatment of ultrasound & enzymatic were obtained at 24 kHz frequency, 100W giving 75% of delignification in 6 h. An enhancement in lignin degradation by 25% and reduction in the treatment time from 12 to 6 h is achieved as compared to only laccase treatment. (C) 2016 Elsevier Ltd. All rights reserved.