The research: "Enhance biogas production by supplementing rice straw"was conducted in batch anaerobic digesters in laboratory conditions. The mixing ratios of rice straw and pig manure were 100 percent pig manure, 20 percent straw+80 percent pig manure, 40 percent straw+60 percent pig manure, 50 percent straw+50 percent pig manure, 60 percent straw +40 percent pig manure, 80 percent straw+20 percent pig manure, and 100 percent straw. Experiments were conducted randomly in batch anaerobk 21L reactors
each mixing ratio was conducted in five replications and monitored in 60 days continuously. The results showed that rice straw have a high potencial of enhancing biogas production due to mixing with pig manure. Mixing ratios of rice straw and pig manure at 50 percent and 60 percent level had the highest gas yield (846.6 and 841.8 L/kg VS degraded) which were not different from other mixing ratios except of 100 percent straw and 100 percent pig manure (P0.05). Supplementing rice straw could enhance the rate of methane in biogas. Rice straw did not affect on temperature, pH, alkalinity and redox potential of fermentation liquid. The digestate had a high concentration of total nitrogen and total phosphorus that could be used as organic fetilizer. The research results strongly reveal that supplementing of rice straw could improve the biogas efficiency of real biogas reactors.