bstract Today, increasing fuel consumption, depletion of fossil fuels, and their environmental problems urge us to find clean and renewable alternatives such as biogas. Lignocellulosic materials are inexpensive, and their use for biofuel production could reduce the environmental pollutions. In this research, pinewood and rice straw, as lignocellulose materials, were used for the production of biogas by aerobic-anaerobic method. In the aerobic-anaerobic method, lignocellulosic biomass was first converted to its monomers and fatty acids during the aerobic stage. In the second stage, these monomers and fatty acids were converted into biogas during the anaerobic digestion. To improve the efficiency of the process, three pretreatments, i.e., ultrasonic, liquid hot water, and alkali sodium hydroxide, were used for pinewood. Also, sodium carbonate pretreatment was performed on rice straw. The sodium hydroxide pretreatment was carried out on pinewood at 100°C for 10 min using 8% (w/v) NaOH solution. The sodium carbonate pretreatment was performed on rice straw at 100°C for 3 h using 0.5 M Na 2 CO 3 solution. For aerobic-anaerobic biogas production, the substrate was subjected to aerobic microbial mixture for 10 days, and then the substrate and the aerobic microbial mixture entered the anaerobic digestion phase for 40 days to produce biogas. The effects of different mechanisms including co-digestion, the biological pretreatment, and the bio-augmentation of aerobic and anaerobic microorganisms on biogas production were investigated. For this purpose, the residue from the aerobic phase was autoclaved and entered the anaerobic digestion phase to investigate bio-augmentation compared to non-autoclaved samples. In addition, the substrates together with aerobic microbial mixture or autoclaved aerobic microbial mixture, directly entered the anaerobic digestion phase to investigate the effect of biological pretreatment and co-digestion, respectively. During the anaerobic digestion, the efficiency of the ultrasonic pretreatment on methane production from raw pinewood was higher than other cases. It increased the methane production from 4.8 to 11.3 mL/g.VS. During the aerobic-anaerobic digestion, these waves had the greatest effect on methane production from hot water-pretreated pinewood. As the methane production yield from hot water-pretreated pinewood was increased from 39.4 mL/g.VS to 45.8 mL/g.VS using the ultrasonic pretreatment. The highest methane production from aerobic-anaerobic digestion of raw pinewood was 76.3 mL/g.VS, which was obtained from the anaerobic digestion of autoclaved aerobic sludge and the substrate. The highest amount of methane yield from sodium hydroxide pretreated pinewood was 208.4 mL/g.VS, which was obtained by autoclaving the substrate after aerobic digestion and entering the anaerobic digestion. The same digestion conditions for rice straw also yielded the highest amount of methane production (215.9 mL/g.VS). The results showed that the use of the aerobic-anaerobic method significantly increased the production of biogas from pinewood and rice straw compared to anaerobic digestion method. Keywords : biogas, pinewood, rice straw, aerobic digestion, bioaugmentation, alkaline pretreatment