The biochemical methane potential of co-digestion of OFMSW (organic fraction of municipal solid waste), TWAS (thickened waste activated sludge) (thermal and thermo-alkaline pretreated) and RS (rice straw) (NaOH and H2O2 pretreated) were investigated in this paper. The batch experiments were conducted at three different OFMSW/TWAS/RS (volume basis) ratios of 1:1.5:1.5, 1:0.5:0.5, and 3:0.5:0.5, respectively. In addition, to predict the biogas yield and evaluate the kinetic parameters, modified Gompertz model was introduced. A 3:0.5:0.5 ratio of OFMSW mixed with thermo-alkaline-treated TWAS and H2O2-treated RS produced the highest biogas production (558.5 L/kgVS(added)) and the highest VS (volatile solids) removal efficiency (76.9%) due to the synergistic effect. The modified Gompertz model (R-2: 0.868-0.998 and 0.910-0.999 for mono- and co-digestions, respectively) showed a good fit to the experimental results and the estimated parameters indicated that the pretreatments and co-digestion of substrates markedly improved the biogas production rate. (C) 2016 Elsevier Ltd. All rights reserved.