In this thesis work, Cellruptor pre-treatment was evaluated in order to increase biogas yield. Initially, the effects of residence time (30, 60, 90, 120 and 180 min) and substrate release (rapid/non-rapid) from the draining port of Cellruptor on biosludges were investigated to find the optimum operating conditions of Cellruptor. Under these optimum operating conditions, the effect of Cellruptor pre-treatment on batch reactors of various substrates and semi-continuous digester of biosludge were investigated at mesophil biosludge, dewatered sludge, digested sludge, fibre sludge, hay, maize silage, minced meat, orange peel, seaweed and yeast. From the initial study, 90 min residence time and rapid release of pre-treated substrate from draining port were found to be optimum operating conditions of Cellruptor. From the batch experiments, Cellruptor pretreatment showed maximum and minimum increase of methane yield in hay (32%) and dewatered sludge (2%) respectively. The semi-continuous digester experimental results showed increase in biogas production by 22.4% from Cellruptor pre-treatment of biosludge at HRT of 15 days and OLR of 2.0 g VS/L/day. With further studies, Cellruptor pre-treatment may be deployed in large-scale biogas plants to improve biogas yield.